Posts Tagged ‘Facial Nerve’

Reporter: Aviva Lev-Ari, PhD, RN

Acoustic Neuroma


Advances in medicine, especially imaging technology have made the identification of small Acoustic Neuromas (AN) possible. After routine auditory tests reveal loss of hearing and speech discrimination (i.e. “I can hear sound in that ear, but can’t understand what’s being said”) a special test for hearing which records responses from the brain-stem called the auditory brainstem response test (ABR, BAER, BSER) maybe done. The results of this test detect the cause of a poorly functioning 8th nerve. If an abnormality in the ABR test suggests an AN, imaging is done to confirm the diagnosis.   I do not perform the ABR test in all patients to diagnose an acoustic neuroma because imaging techniques (MRI/CT scans) are the gold standard for diagnosis. CT scan has proven to be a powerful tool in locating AN’s. The only drawback is that small tumors confined to the internal auditory canal (IAC) may not show on plain CT scan. Such cases require air or contrast materials to be introduced into the body in order to enhance the tumor. Therefore, the MRI, a more recently developed diagnostic test, has become the gold standard for diagnosis of AN. Gadolinium is the contrast material used to define & enhance the tumor.

Small tumorsA small tumor is also called intracanalicular because it is confined within the bony internal auditory canal (figure). A patient with such a tumor may have hearing loss, ringing in the ear or ear noise, and vertigo or dizziness. 
Medium tumorsA medium sized acoustic neuroma is one that has extended from the bony canal into the brain cavity, but has not yet produced pressure on the brain itself (figure). Patients with such tumors have worsening of their hearing, difficulty in balance, in addition to dizziness, and occasionally, the onset of headaches due to irritation of the lining of the brain called dura. Some patients may experience numbness of the mid-face or diminished sensation in the eye during the later stages. 
Large tumorsA large tumor is one that is extended out of the internal auditory canal in to the brain cavity and is sufficiently large to produce pressure on the brain and disturb vital centers in the brain (figure). During this stage, all previous symptoms worsen; facial twitch and weakness may occur, and finally patient may develop hydrocephalus due to the blockage of the cavity which contains CSF-the resultant symptoms are headache, visual loss and double vision. 


The AN usually arises within the nerve trunk of the vestibular part of the 8th nerve. It gradually grows out of the nerve as it increases in size and assumes a peripheral position. The AN’s usually arise halfway along the length of the vestibular nerve, which corresponds to the transition zone of the nerve structure. The typical microscopic appearance of AN’s has two distinct features of arrangement of the cells-either tightly packed (Antoni A) or loosely packed (Antoni B) fibers. The distinction of these two cell types is of no clinical importance. Indeed, regions of Antoni A and B may coexist in the same tumor. As the tumor grows, it follows the direction of least resistance, usually towards the brain (cerebellopontine angle) and may reach considerable size. Thus, most tumors consist of 2 parts: a stalk or stem within the internal auditory canal (IAC) and another portion near the brain region. Microscopic investigations into the effect of AN’s on adjacent facial or 7th nerve have shown tumor involvement in some cases. This involvement may not be recognized by the surgeon during removal of the AN.

This picture shows the microscopic appearance of a normal vestibular (8th) nerve passing through the internal auditory canal (IAC) to supply the organ of balance. The facial (7th) nerve runs along with the 8th nerve in the IAC. The organ of hearing (cochlea) is also seen in this picture.
This picture shows an AN tumor arising from the 8th nerve, within the IAC.
This is a higher magnification of the above picture showing the junction of the tumor and the VII nerve. The arrows indicate the sheath (covering layer) of the tumor.
This picture is a high magnification of the same tumor showing the arrangement of the fibers within the AN. The arrow indicates a whorled appearance of the fibers while the upper part of the tumor shows loosely packed (Antoni B) fibers.

Origin and Cause

diagram of ear

Origin and Cause

What is an acoustic neuroma? 

An acoustic neuroma (sometimes also termed a neurinoma or vestibular schwannoma) is a benign or non-cancerous growth that arises from the 8th or vestibulo-cochlear nerve. The 8th nerve is actually 2 separate nerves, the vestibular nerve and the cochlear nerve. The vestibular nerve is responsible for balance while the cochlear nerve is responsible for hearing. The vestibular nerve has 2 parts-the superior vestibular nerve (SVN) and the inferior vestibular nerve (IVN).These nerves lie adjacent to each other as they pass through a bony canal, from the inner ear to the brainstem. This bony canal is called the internal auditory canal (IAC) and it varies in length from 0.4 to 1.2 cm. We have two figures of a temporal bone (that part of the skull which has the ear in it) dissection to the right.The first figure is a view from the top showing the middle ear and the internal auditory canal (IAC) with the nerves passing through it. The organ of hearing (cochlea) and the dura lining the IAC can be seen clearly.The second figure is a magnification of the IAC region showing the different nerves passing through it. This figure also demonstrates clearly, the cochlear nerve supplying the cochlea. Acoustic neuromas usually arise from the cells of the VIII nerve within the internal auditory canal (third figure).

The third figure is a schematic drawing showing an acoustic neuroma arising from the vestibular nerve within the IAC. The facial or 7th nerve that is responsible for facial movement, along with important blood vessels, also passes with the 8th nerve in the canal (figures).

The cause of acoustic neuroma is unknown. A small percentage of individuals have a hereditary condition called neurofibromatosis type 2 (NF-2). These patients may have an acoustic neuroma on both sides with an aggressive growth pattern and often involve adjacent nerves.

What is the growth pattern? 

Acoustic neuromas usually grow very slowly over a period of many years. Once the tumor fully occupies the internal auditory canal, it often begins to erode the walls of the canal and enlarges it. This bony erosion however, does not always occur. They typically remain within their capsule or lining and displace the surrounding nerves and brain tissue very slowly. This is why the body has ample time to accommodate the abnormal growth. The tumor first distorts the 8th nerve, and then presses on the adjacent 7th nerve. The 7th nerve is gradually stretched into a ribbon like structure over the enlarging tumor (figure; cross section of the 7th nerve is shown in the right half of the figure). As the tumor slowly enlarges towards the brain, it protrudes from the internal auditory canal into an area of the skull called cerebello-pontine angle. The tumor is now pear or mushroom shaped with the smaller end within the canal and the larger part towards the brain (figure). It is at this stage that the tumor presses adjacent nerves like the trigeminal or 5th nerve responsible for facial sensation. Ultimately, with increasing tumor size, it can press on the brainstem which can be life threatening.

How often do acoustic neuromas occur?

Acoustic neuromas have been known to occur in all areas of the world without any predilection for individuals of any ethnic background. Small AN’s without any symptoms, have been found on autopsy in 2.5% of the general population. Estimates of symptomatic AN range from 1 in every 3,500 to 5 in every million people. It appears that women are more affected than men and most AN’s are diagnosed between the ages of 30 & 60 years.

For more information, you may visit the Acoustic Neuroma Association Web site

Early symptoms of AN can occur in other conditions of the ear that can be easily overlooked. Early diagnosis of AN is quite challenging because there is no typical pattern. However, there are symptoms that act as indicators to the possibility if an AN. Patients with “inner ear” problems should be completely evaluated to rule out AN as a cause of these symptoms. It is possible that Meniere’s disease or hardening of the bone of the middle ear (otosclerosis) could be causing these symptoms. Patients with AN may present the following symptoms:

  • Hearing loss
  • Ringing in the ears (tinnitus)
  • Dizziness (vertigo)
  • Difficulty in balance (imbalance or dysequilibrium)
  • Fullness or pressure in the ears
  • Facial numbness or paralysis (for very large tumors)

In over 90 percent of the patients with AN, the first symptom is a reduction in hearing in one ear due to involvement of the VIII nerve. This is usually accompanied by ringing in the ears or ear noise-also called “tinnitus”. The hearing loss is usually subtle and worsens very slowly over a period of time. In some cases, the hearing loss may be sudden. Some patients may experience a sense of fullness in the affected ear. Unfortunately, since hearing loss is often mild and there is no pain, patients tend to ignore the change in hearing and merely shift the phone to the opposite ear or make other compromises for the one-sided hearing loss rather than seek medical attention.

The tumor usually arises from the vestibular or balance nerve.  As a result, unsteadiness or balance problems may be one of the earlier symptoms in the growth of the tumor. Since the remainder of the balance system compensates for this loss, balance problems may be forgotten after some time.

If the tumor grows larger in size it may start to press on other nerves, mainly the trigeminal nerve, causing facial sensation to become affected.  Patients may then experience constant or intermittent numbness and facial tingling. Patients may also have facial tics or spasms. If the tumor grows larger and presses on the brainstem raised intracranial pressure may cause headaches, facial weakness, vertigo and an unsteady gait to ensue.

There are 3 treatment options available for AN

1) Observation

2) Microsurgical removal (partial or total)

3) Stereotactic radiation therapy (radiosurgery)

AN are occasionally discovered incidentally while evaluating another problem or when the tumor is very small with subtle symptoms. Since AN are benign tumors and produce symptoms due to pressure on surrounding structures, careful observation over a period of time may be appropriate for some patients. For instance, a small tumor diagnosed in an elderly patient may only require observation to study the growth rate of the tumor if acute symptoms are not present. If it appears that the tumor will not need to be treated during the patient’s normal life expectancy, treatment and its potential risks and complications maybe avoided. In these patients, MRI is performed periodically to monitor growth of the tumor. If there is no growth, observation is continued. On the other hand, if the tumor shows increase in size, treatment may become necessary. Another group of patients for whom observation is preferred is in patients who have a tumor in their only or better hearing ear, particularly if it is a size where hearing preservation is unlikely. In such cases, periodic MRI is done to monitor growth and surgery is considered only if the hearing is lost or the tumor size becomes life threatening.

Microsurgical removal
At the present time, the only treatment that can cure the patient is removal of the tumor by surgery. Within the last 2 decades, microsurgical techniques have been pioneered and refined. Use of the operating microscope, finely scaled surgical instruments, alternate cutting & tumor reducing tools, and better anesthesia, have reduced the death rate extremely. In addition, results have improved as surgeons have gained experience in the delicate removal process of the tumor.

Three main surgical approaches are used depending upon the location, tumor size and hearing level of the patient. They are- middle fossa (MF), sub-occipital (SO), and the trans-labyrinthine (TL) approach. Surgery for AN’s is done under general anesthesia using an operating microscope. Postoperatively, one to several days may be spent in the intensive care with careful monitoring. Problems that may develop in the immediate postoperative period including headache, dizziness, imbalance, vomiting and decreased mental alertness due to the development of a blood clot causing obstruction to the flow of cerebrospinal fluid (CSF).

Other early complications may include cerebrospinal fluid leak and meningitis, an infection controlled with antibiotics that will require a longer hospitalization. Some patients and their surgeons prefer incomplete removal of an AN in order to reduce the risk of complications, realizing that further surgery maybe needed in the future. Occasionally in cases with large tumors, disturbances in the vital brain centers during surgery require ending the surgery prior to complete tumor removal. In these cases, the tumor which was left behind is followed with MRI scans and if tumor growth is demonstrated, further surgery maybe necessary to remove the growing tumor. On the other hand, if the tumor shows no growth, observation is continued. Partial tumor removal maybe also be required in a patient with an only hearing ear such as a Neurofibromatosis-2 (NF 2) patient. Unfortunately, partial removal may result in substantial hearing loss in these patients and this risk must be considered.

Small tumor

If the hearing is still preserved in such tumors, a middle fossa approach, incision for which is in front of the ear (figure) may be considered. A small square piece of bone from the side of the skull is then removed (blue shaded area in the figure). The tumor is removed completely in most cases. On rare occasions, partial removal is possible. This approach attempts to preserve the hearing in all cases while removing the tumor. In about half of the patients, the tumor involves the hearing nerve or the artery supplying the inner ear and in such cases, total loss of hearing occurs in the operated ear.  In addition, the risk to the facial nerve is far greater in this approach/

Medium tumor

The operation for medium sized tumors is performed by the sub-occipital and/or the trans-labyrinthine approach. The incision for these approaches is behind the ear, overlying the mastoid, the bony projection felt behind the ear (figures). The mastoid and the inner ear structures are removed to expose the tumor, and remove it completely. The opening created in the mastoid bone is closed with fat taken from the abdomen. The translabyrinthine approach sacrifices the hearing and balance mechanism since the inner ear is entered. Consequently, the ear is made permanently deaf. In such cases, the balance mechanism of the opposite ear compensates for the non-functioning operated ear and provides stabilization for the patient within few weeks to months.

Large tumor

Surgery for large tumors requires extensive removal of bone to properly expose the tumor and control the large blood vessels that make access to the tumor difficult. For this reason, special studies of the arteries (arteriograms) may be required in addition to the other investigations, in order to diagnose and establish the size of the acoustic tumor. The operation for large tumors is performed by the TL-SO approach as described for medium tumors. The figure to the right shows the area of the skull approached via the TL and the SO approaches. In these patients, total removal is attempted unless changes in vital signs occur. If there are changes in blood pressure, pulse rate, or respiratory rate, the surgery must be terminated even if the tumor has not been totally removed. The opening in the mastoid is closed with abdominal fat. For large tumors, it is often necessary to monitor the patient’s general status by inserting a small tube (arterial line) into an artery in the arm or leg. In these cases, occasionally a blood clot may form in the artery following surgery. In case this complication occurs, further surgery maybe required to remove the blood clot. A very rare complication of this arterial line monitoring is the loss of a finger, toe, or even a hand or a foot.

Stereotactic Radiation Therapy (Radiosurgery):
This is a technique based on the principle that a single relatively high dose of radiation delivered precisely to a small area will arrest or kill the tumor while minimizing injury to the surrounding nerves & brain tissue. The source of radiation is from either radioactive cobalt (called gamma ray) or a linear accelerator (LINAC). The treatment team consists of a neurosurgeon, radiophysicist and a radiation oncologist working together to develop a treatment plan based on the size & shape of the tumor. Radiation, even at relatively high doses such as those used in radiosurgery, does not kill or injure cells immediately. Some tumor cells die in weeks while others die more gradually over 6-18 months after radiation. This treatment usually arrests growth of the tumor and some tumors shrink, but they rarely disappear.

Follow-up of these patients is important because approximately 20% of tumors continue to grow after radiosurgery or at some time in the future. A tumor that has been irradiated and grows may be more difficult to remove than an un-radiated tumor. Symptoms such as dizziness & disturbances in balance typically improve earlier after microsurgical tumor removal than after radiosurgery. This is because effects of radiosurgery may require up to 18 months. Residual dizziness & imbalance may be less after microsurgical treatment. The side effects of radiosurgery may be headache, dizziness, nausea, facial numbness, or rarely, cranial nerve paralysis. In the long term requires follow-up MRI’s over the years and there is a potential for additional treatment in cases of continued growth or later re-growth.

Microsurgery requires follow-up MRI’s suggested at perhaps 1 and 5 years if the tumor has been completely removed. Radiosurgery may be considered in selected patients in whom the risk of surgery is excessive because of advanced age or pre-existing health problems, patients having small to moderate sized tumors or patients with tumors on both sides, or in the only hearing ear.


Microsurgery of an AN is a complex and delicate procedure. The smaller the tumor at the time of surgery, the fewer the chances are for complications. As the tumor size increases, the chances of complications become greater. Thus, there may be problems with the cranial nerves affected by the tumor (like facial paralysis or hearing loss) following surgery that may or may not have been present before tumor removal.  Here is a list of some of the more common post-operative issues and problems encountered.

Residual problems

This period is the days or perhaps weeks following surgery. There is a possibility of fatigue or tiredness and increased drowsiness, although some patients may experience “survival euphoria” and a renewed sense of energy and vigor. A period of emotional lows is common as the patient adjusts to physical changes. One symptom that may occur after discharge is a nasal drip of clear colorless fluid, which is particularly noticeable when bending over. This may indicate a cerebrospinal fluid leak and should be reported to the surgeon right away due to the risk of infection.

Follow-up period :After being discharged from the hospital, patients operated for an AN are followed up regularly (every 2-3 months for the first year, every 6 months for the 2nd year, and every year thereafter). These follow up visits are important to monitor the hearing (in patients operated by the MF or SO approach), facial nerve paralysis if any and for recurrence of tumor.

With small tumors, it may be possible to save hearing. In larger tumors, especially those that have extended into the brain cavity, the hearing has usually been partially or totally lost and cannot be restored. This loss means the patient will continue having problems locating sound, hearing on the deaf side and understanding speech over high background noise. Consultation with an audiologist is required for these patients for amplification options like traditional hearing aids or a CROS hearing aid (a device which crosses sound over from the operated ear to the opposite ear) or a BAHA.

Ear noises usually remain the same as before surgery, though in a few cases noises may increase or begin after surgery. A masking device may help some people affected by tinnitus.

Since the facial nerve which controls muscles of facial expression is in close proximity with the AN, it is usually necessary to manipulate and at times remove the portion of the nerve. In some cases however, even though the nerve is intact after surgery, nerve damage or swelling may cause temporary or in some cases permanent facial paralysis. Regrowth of the nerve is a slow process that may take up to a year for recovery to be noticeable. If recovery is not observed by 1 year, a second operation may be required to connect the healthy portion of the facial nerve to a nerve in the neck usually the one supplying one side of the tongue. This procedure is called the hypoglossal-facial nerve anastamosis and can restore some but not all facial movement. Spontaneous movements like laughing are asymmetric. There may be loss of tongue function. There are some other procedures that adapt available muscles and nerves to help in toning or reanimating the sagging face. If it becomes necessary to remove a portion of the facial nerve during surgery, the facial nerve may be reconnected directly or by inserting a nerve graft. Usually, the result is asymmetric but will provide some spontaneous movement.


Studies have shown that at least half of those who have had an acoustic neuroma removed develop long term eye discomfort and other eye problems, particularly if the tumor was medium or large. Loss of eyelid function and/or altered tear production can cause irritation and scratchiness in the eye because it is dry & unprotected. To deal with this problem, there are various surgical procedures that can be done to protect the cornea. They include canthoplasty (bringing together tendons in either or both corners of the eye), a spring implantation in the upper lid, an elastic prosthesis secured around the upper and lower lids, a gold weight implant in the upper lid; and a tarsorapphy (sewing the lids together). Artificial tears or eye lubricants maybe needed for a short time or permanently. Taping part of the lids together, using protective glasses and moisture chamber, using bandage contact lenses and avoiding eye irritants may be helpful. In a few patients, double vision may be present due to pressure on the 6th cranial nerve that controls the muscles that move the eyes.

There maybe some changes in taste and amount of saliva secretion for a short time following surgery. In some cases this may be prolonged. In the others, increased salivation occurs while chewing or there maybe increased tearing while eating. The appetite maybe affected for some time.

In a small number of patients, AN surgery affects the nerves which control the throat, swallowing and voice production leading to hoarseness & difficulty in swallowing. These symptoms usually improve slowly over time.

The vestibular portion of the VIII nerve is almost always removed during surgery. Usually this part of the nerve is non-functional and has already been destroyed because of the AN. Dizziness is common following surgery and maybe severe for a time. After a while, the balance apparatus of the opposite or normal ear compensates for this loss, and balance improves. This compensation may not be perfect, particularly in darkness, when the patient is fatigued, when there is a sudden change in body position, or while walking on uneven surfaces. Maintaining a good general physical health through proper diet and moderate exercise, can improve balance & general vitality to a great extent.

Fatigue sometimes remains a prolonged problem for some patients after some of the other symptoms have subsided. It is important in such patients to adjust their pace of life in harmony with their energy level.


Headaches can be a problem for some patients while still in the hospital. This maybe related to tension from holding the head rigidly, changes in intracranial pressure, muscle spasm, or anxiety. Headaches are almost never related to tumor recurrence. Treatment is with analgesics & muscle relaxation. If severe headaches persist after hospital discharge, medical help should be sought.

If the patient has facial paralysis, food tends to get lost in the mouth on the affected side and can lead to dental problems. Washing and rinsing the mouth is therefore necessary, as well as brushing & flossing the teeth several times a day is important.

It is important to provide sensible protection to the opposite or good ear that has the remaining hearing apparatus. This is done by avoiding extreme or sudden exposure to loud noises like firearms or some cordless phones near the good ear. Some physicians suggest follow-up MRI scans and/or audiograms for some time following AN removal.

For some patients, adjustment to a new self after AN removal can be a challenging task. This is because in addition to changes in hearing, the appearance may now be altered along with the presence of other impairments. Return to normal activity may be slow. Concentrating on strengths rather than on weaknesses will help such patients to return to all former activities and also expand their abilities in new areas.



Proton beam radiosurgery for vestibular schwannoma: tumor control and cranial nerve toxicity.

Weber DCChan AWBussiere MRHarsh GR 4thAncukiewicz MBarker FG 2ndThornton ATMartuza RLNadol JB JrChapman PHLoeffler JS.


Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts, USA. damien.weber@psi.ch



We sought to determine the tumor control rate and cranial nerve function outcomes in patients with vestibular schwannomas who were treated with proton beam stereotactic radiosurgery.


Between November 1992 and August 2000, 88 patients with vestibular schwannomas were treated at the Harvard Cyclotron Laboratory with proton beam stereotactic radiosurgery in which two to four convergent fixed beams of 160-MeV protons were applied. The median transverse diameter was 16 mm (range, 2.5-35 mm), and the median tumor volume was 1.4 cm(3) (range, 0.1-15.9 cm(3)). Surgical resection had been performed previously in 15 patients (17%). Facial nerve function (House-Brackmann Grade 1) and trigeminal nerve function were normal in 79 patients (89.8%). Eight patients (9%) had good or excellent hearing (Gardner-Robertson [GR] Grade 1), and 13 patients (15%) had serviceable hearing (GR Grade 2). A median dose of 12 cobalt Gray equivalents (range, 10-18 cobalt Gray equivalents) was prescribed to the 70 to 108% isodose lines (median, 70%). The median follow-up period was 38.7 months (range, 12-102.6 mo).


The actuarial 2- and 5-year tumor control rates were 95.3% (95% confidence interval [CI], 90.9-99.9%) and 93.6% (95% CI, 88.3-99.3%). Salvage radiosurgery was performed in one patient 32.5 months after treatment, and a craniotomy was required 19.1 months after treatment in another patient with hemorrhage in the vicinity of a stable tumor. Three patients (3.4%) underwent shunting for hydrocephalus, and a subsequent partial resection was performed in one of these patients. The actuarial 5-year cumulative radiological reduction rate was 94.7% (95% CI, 81.2-98.3%). Of the 21 patients (24%) with functional hearing (GR Grade 1 or 2), 7 (33.3%) retained serviceable hearing ability (GR Grade 2). Actuarial 5-year normal facial and trigeminal nerve function preservation rates were 91.1% (95% CI, 85-97.6%) and 89.4% (95% CI, 82-96.7%). Univariate analysis revealed that prescribed dose (P = 0.005), maximum dose (P = 0.006), and the inhomogeneity coefficient (P = 0.03) were associated with a significant risk of long-term facial neuropathy. No other cranial nerve deficits or cancer relapses were observed.


Proton beam stereotactic radiosurgery has been shown to be an effective means of tumor control. A high radiological response rate was observed. Excellent facial and trigeminal nerve function preservation rates were achieved. A reduced prescribed dose is associated with a significant decrease in facial neuropathy.

Proton Beam Radiosurgery (Neurosurgery)

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The Proton Beam Unit was founded in 1962 and has the largest experience with stereotactic radiosurgery of any center in the United States. Information regarding non-invasive proton beam radiosurgery and fractionated radiosurgery for brain and spinal tumors and arteriovenous malformations.The Purpose of this Center is to provide a complete range of services for the diagnosis, and treatment with non-invasive proton beam radiosurgery and fractionated radiosurgery for brain and spinal tumors and arteriovenous malformations. Patients may be referred for consultation only, care in partnership with referring physician, or complete management.

Bragg Peak Proton Beam Radiosurgery Unit – The Proton Beam Unit was founded in 1962 and has the largest experience with stereotactic radiosurgery of any center in the United States. Proton beam offers certain theoretical advantages over other modalities of stereotactic radiosurgery (i.e. gamma knife and linear accelerators) because it makes use of the quantum wave properties of protons to reduces doses to surrounding tissue beyond the target to a theoretical minimum of zero. In practice, the proton facility offers advantages for the treatment of unusually shaped brain tumors and arteriovenous malformations. The homogeneous doses delivered also makes fractionated therapy possible. Proton beam radiosurgery also has the ability to treat tumors outside of the cranial cavity. These properties make it the ideal post-resection therapy for many chordomas and certain chondrosarcomas of the spine and skull base as well as an excellent mode of therapy for many other types of tumors.

HCL: The Harvard Cyclotron Laboratory (HCL) has now closed. The ‘Particles Newsletters’ have been transfered to the MGH PTCOG web and the main PSI-PTCOG system.

NPTC: Information, proton radiosurgery treatments and support services have been transfered to the new The Northeast Proton Therapy Center (NPTC). Located on the main hospital campus of the Massachusetts General Hospital (MGH), the NPTC represents the forefront of technological advancement in radiation therapy. The construction of the facility was jointly funded by the hospital and the National Cancer Institute to meet the increasing medical demand for high precision radiation therapy provided by proton therapy. The program builds on more than forty years of pioneering work and experience gained by the physicians, physicists, and clinical support personnel at Harvard University’s Cyclotron Laboratory where more than nine thousand patients were treated with proton therapy from 1961 to it’s closing in 2002.


Selected Publications

  • Rabinov JD, Brisman JL, Cole AJ, Lee PL, Bussiere MR, Chapman PH, Loeffler JS, Cosgrove GR, Chaves T, Gonzalez RG.: MRI changes in the rat hippocampus following proton radiosurgery. Stereotact Funct Neurosurg. 2004;82(4):156-64.
  • Brisman JL, Cole AJ, Cosgrove GR, Thornton AF, Rabinov J, Bussiere M, Bradley-Moore M, Hedley-Whyte T, Chapman PH.: Radiosurgery of the rat hippocampus: magnetic resonance imaging, neurophysiological, histological, and behavioral studies. Neurosurgery. 2003 Oct;53(4):951-61; discussion 961-2.
  • Weber DC, Chan AW, Bussiere MR, Harsh GR 4th, Ancukiewicz M, Barker FG 2nd, Thornton AT, Martuza RL, Nadol JB Jr, Chapman PH, Loeffler JS.: Proton beam radiosurgery for vestibular schwannoma: tumor control and cranial nerve toxicity. Neurosurgery. 2003 Sep;53(3):577-86; discussion 586-8.
  • Barker FG 2nd, Butler WE, Lyons S, Cascio E, Ogilvy CS, Loeffler JS, Chapman PH.: Dose-volume prediction of radiation-related complications after proton beam radiosurgery for cerebral arteriovenous malformations. J Neurosurg. 2003 Aug;99(2):254-63.
  • Harsh GR, Thornton AF, Chapman PH, Bussiere MR, Rabinov JD, Loeffler JS.: Proton beam stereotactic radiosurgery of vestibular schwannomas. Int J Radiat Oncol Biol Phys. 2002 Sep 1;54(1):35-44.
  • Barker FG 2nd, Amin-Hanjani S, Butler WE, Lyons S, Ojemann RG, Chapman PH, Ogilvy CS.: Temporal clustering of hemorrhages from untreated cavernous malformations of the central nervous system. Neurosurgery. 2001 Jul;49(1):15-24; discussion 24-5.
  • Chapman PH, Tarbell: Proton beam therapy. In: Pediatric Neurosurgery. Surgery of the Developing Nervous System, 4th ed. Ed: McLone DG: WB Saunders: Philadelphia, pp. 1255-1262, 2001.
  • Loeffler JS, Singer RJ, Chapman PH, Ogilvy CS: Proton-beam radiation therapy. In: LINAC and Gamma Knife Radiosurgery. Ed: Germano IM. The American Association of Neurological Surgeons: Park Ridge, IL, pp. 71-74, 2000.
  • Harsh G, Loeffler JS, Thornton A, Smith A, Bussiere M, Chapman PH: Stereotactic Proton Radiosurgery. Neurosurg Clin N Am 1999; 10:243-256.
  • Tatter SB, Butler WE, Chapman PH. Technical and clinical aspects of proton-beam stereotactic radiosurgery. In: Textbook of Stereotactic and functional Neurosurgery. Eds: Gildenberg PL, Tasker RR. McGraw-Hill, New York pp. 705-710, 1998.
  • Serago CF, Thornton AF, Urie MM, Chapman P, Verhey L, Rosenthal SJ, Gall KP, Niemierko A: Comparison of proton and x-ray conformal dose distributions for radiosurgery applications. Med Phys 22:2111-16, 1995.
  • Butler WE, Ogilvy CS, Chapman PH, Verhy L , Zervas NT. “Stereotactic alignment for Bragg peak radiosurgery.” In Radiosurgery: Baseline and Trends, ed. L. Steiner. 85-91. New York: Raven Press, 1992.
  • Chapman PH, Ogilvy CS , Butler WE. “A new stereotactic alignment system for charged-particle radiosurgery at the Harvard Cyclotron Laboratory, Boston.” In Stereotactic Radiosurgery, ed. Eben Alexander III, Jay S. Loeffler, and L. Dade Lunsford. 105-108. New York: McGraw-Hill, 1993.
  • De Salles AA, Asfora WT, Abe M, Kjellberg RN: Transposition of target information from the magnetic resonance and computed tomography scan images to conventional X-ray stereotactic space. Applied Neurophysiology 50: 23-32, 1987.
  • Gall KP, Verhey LJ, Wagner M: Computer-assisted positioning of radiotherapy patients using implanted radiopaque fiducials. Medical Physics 20: 1153-9, 1993.
  • Kjellberg RN, Hanamura T, Davis KR, Lyons SL , Adams RD: Bragg-peak proton-beam therapy for arteriovenous malformations of the brain. New England Journal of Medicine 309: 269-74, 1983.
  • Kjellberg RN, Shintani A, Frantz AG, Kliman B: Proton-beam therapy in acromegaly. New England Journal of Medicine 278: 689-95, 1968.
  • Urie MM, Fullerton B, Tatsuzaki H, Birnbaum S, Suit HD, Convery K, Skates , Goitein M: A dose response analysis of injury to cranial nerves and/or nuclei following proton beam radiation therapy. International Journal of Radiation Oncology, Biology, Physics 23: 27-39, 1992.


Radiotherapy for vestibular schwannomas: a critical review.


Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH 44195, USA. murphye3@ccf.org


Vestibular schwannomas are slow-growing tumors of the myelin-forming cells that cover cranial nerve VIII. The treatment options for patients with vestibular schwannoma include active observation, surgical management, and radiotherapy. However, the optimal treatment choice remains controversial. We have reviewed the available data and summarized the radiotherapeutic options, including single-session stereotactic radiosurgery, fractionated conventional radiotherapy, fractionated stereotactic radiotherapy, and proton beam therapy. The comparisons of the various radiotherapy modalities have been based on single-institution experiences, which have shown excellent tumor control rates of 91-100%. Both stereotactic radiosurgery and fractionated stereotactic radiotherapy have successfully improved cranial nerve V and VII preservation to >95%. The mixed data regarding the ideal hearing preservation therapy, inherent biases in patient selection, and differences in outcome analysis have made the comparison across radiotherapeutic modalities difficult. Early experience using proton therapy for vestibular schwannoma treatment demonstrated local control rates of 84-100% but disappointing hearing preservation rates of 33-42%. Efforts to improve radiotherapy delivery will focus on refined dosimetry with the goal of reducing the dose to the critical structures. As future randomized trials are unlikely, we suggest regimented pre- and post-treatment assessments, including validated evaluations of cranial nerves V, VII, and VIII, and quality of life assessments with long-term prospective follow-up. The results from such trials will enhance the understanding of therapy outcomes and improve our ability to inform patients.

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Reporter: Aviva Lev-Ari, PhD, RN

In researching Intracanalicular Meningiomas, Vestibular Schwannomas — we presented on 10/15/2012 the following article:

Facial Nerve, Intracanalicular Meningiomas, Vestibular Schwannomas: Surgical Planning


Our research continues by tracing all Clinical Trials – active for Schwannoma

1 Recruiting Intraarterial Cerebral Infusion of Avastin for Vestibular Schwannoma (Acoustic Neuroma)

Condition: Vestibular Schwannoma
Intervention: Drug: Bevacizumab (Avastin)
2 Active, not recruiting Bevacizumab for Symptomatic Vestibular Schwannoma in Neurofibromatosis Type 2 (NF2)

Conditions: Neurofibromatosis 2;   Vestibular Schwannoma;   Acoustic Neuroma
Intervention: Drug: bevacizumab
3 Active, not recruiting Stereotactic Radiation in Vestibular Schwannoma

Condition: Vestibular Schwannoma
Interventions: Radiation: stereotactic radiotherapy;   Radiation: stereotactic radiosurgery
4 Not yet recruiting Study of RAD001 for Treatment of NF2-related Vestibular Schwannoma

Conditions: Neurofibromatosis Type 2;   Neuroma, Acoustic
Intervention: Drug: RAD001, everolimus
5 Active, not recruiting Efficacy and Safety Study of RAD001 in the Growth of the Vestibular Schwannoma(s) in Neurofibromatosis 2 (NF2) Patients

Condition: Neurofibromatosis 2
Intervention: Drug: RAD001
6 Recruiting Concentration and Activity of Lapatinib in Vestibular Schwannomas

Conditions: Vestibular Schwannoma;   NF2;   Neurofibromatosis 2;   Acoustic Neuroma;   Auditory Tumor
Intervention: Drug: lapatinib
7 Recruiting Hearing Outcomes Using Fractionated Proton Radiation Therapy for Vestibular Schwannoma

Conditions: Vestibular Schwannoma;   Acoustic Neuroma
Intervention: Radiation: Fractionated proton radiation
8 Recruiting A Study of Nilotinib in Growing Vestibular Schwannomas

Conditions: Volumetric Tumor Response and Lack of Tumor Progression;   Quality of Life of Patients on Nilotinib Versus Not
Intervention: Drug: Nilotinib
9 Active, not recruiting Lapatinib Study for Children and Adults With Neurofibromatosis Type 2 (NF2) and NF2-Related Tumors

Conditions: Neurofibromatosis 2;   Vestibular Schwannoma
Intervention: Drug: Lapatinib
10 Recruiting Stereotactic Body Radiotherapy for Spine Tumors

Conditions: Spinal Metastases;   Vertebral Metastases;   Benign Spinal Tumors;   Chordoma;   Meningioma;   Schwannoma;   Neurofibroma;   Paragangliomas;   Arteriovenous Malformations
Intervention: Radiation: stereotactic body radiotherapy
11 Recruiting Natural History Study of Patients With Neurofibromatosis Type 2

Conditions: Spinal Cord Disease;   Intracranial Central Nervous System Disorder;   Neurologic Disorders;   Brain Neoplasms
12 Recruiting Using Positron Emission Tomography to Predict Intracranial Tumor Growth in Neurofibromatosis Type II Patients

Conditions: Neoplasms;   Nervous System Disease;   Vestibular Disease
13 Unknown  Hippocampal Radiation Exposure and Memory

Conditions: Arteriovenous Malformation;   Schwannoma;   Trigeminal Neuralgia
14 Completed Recovery of Visual Acuity in People With Vestibular Deficits

Conditions: Vestibular Neuronitis;   Vestibular Neuronitis, Bilateral;   Vestibular Schwannoma
Interventions: Other: Control exercises;   Other: gaze stabilization exercises
15 Recruiting Bevacizumab in Treating Patients With Recurrent or Progressive Meningiomas

Conditions: Acoustic Schwannoma;   Adult Anaplastic Meningioma;   Adult Ependymoma;   Adult Grade I Meningioma;   Adult Grade II Meningioma;   Adult Meningeal Hemangiopericytoma;   Adult Papillary Meningioma;   Neurofibromatosis Type 1;   Neurofibromatosis Type 2;   Recurrent Adult Brain Tumor
Intervention: Biological: bevacizumab
16 Unknown  NF2 Natural History Consortium

Conditions: Schwannoma, Vestibular;   Neurofibromatosis 2;   Meningioma
17 Completed Analysis of NF2 Mutations in Radiation-Related Neural Tumors

Condition: Neural Tumors
18 Completed Corticosteroids in Prevention of Facial Palsy After Cranial Base Surgery

Condition: Facial Palsy
Intervention: Drug: methylprednisolone
19 Recruiting Phase II Study of Everolimus (RAD001) in Children and Adults With Neurofibromatosis Type 2

Condition: Neurofibromatosis Type II
Intervention: Drug: Everolimus (RAD001) , Afinitor®
20 Completed Phase II Study of Imatinib Mesylate in Patients With Life Threatening Malignant Rare Diseases

Condition: Life Threatening Diseases
Intervention: Drug: Imatinib mesylate
21 Recruiting Taste Disorders in Middle Ear Disease and After Middle Ear Surgery

Condition: Taste Disturbance
Interventions: Other: taste measurement;   Other: Symptom questionnaire;   Behavioral: Quality of life questionnaire;   Other: Nerve sample
22 Completed Vasopressin and V2 Receptor in Meniere’s Disease

Condition: Meniere Disease
Intervention: Genetic: vasopressin, V2 receptor and cyclic AMP
23 Recruiting Gemcitabine and Docetaxel in Combination With Pazopanib (Gem/Doce/Pzb) for the Neoadjuvant Treatment of Soft Tissue Sarcoma (STS)

Conditions: Sarcoma;   Leiomyosarcoma;   Malignant Peripheral Nerve Sheath Tumor;   Malignant Fibrous;   Histiocytoma/Undifferentiated Pleomorphic Sarcoma
Intervention: Drug: Gemcitabine and Docetaxel in Combination with Pazopanib
24 Recruiting Pazopanib Hydrochloride Followed By Chemotherapy and Surgery in Treating Patients With Soft Tissue Sarcoma

Conditions: Adult Alveolar Soft-part Sarcoma;   Adult Angiosarcoma;   Adult Desmoplastic Small Round Cell Tumor;   Adult Epithelioid Hemangioendothelioma;   Adult Epithelioid Sarcoma;   Adult Extraskeletal Chondrosarcoma;   Adult Fibrosarcoma;   Adult Leiomyosarcoma;   Adult Liposarcoma;   Adult Malignant Fibrous Histiocytoma;   Adult Malignant Hemangiopericytoma;   Adult Malignant Mesenchymoma;   Adult Neurofibrosarcoma;   Adult Synovial Sarcoma;   Dermatofibrosarcoma Protuberans;   Stage IIA Adult Soft Tissue Sarcoma;   Stage III Adult Soft Tissue Sarcoma;   Stage IV Adult Soft Tissue Sarcoma
Interventions: Drug: pazopanib hydrochloride;   Drug: doxorubicin hydrochloride;   Drug: ifosfamide;   Other: placebo;   Procedure: therapeutic conventional surgery;   Radiation: external beam radiation therapy;   Other: pharmacological study;   Other: laboratory biomarker analysis
25 Active, not recruiting Trial of Dasatinib in Advanced Sarcomas

Conditions: Rhabdomyosarcoma;   Malignant Peripheral Nerve Sheath Tumors;   Chondrosarcoma;   Sarcoma, Ewing’s;   Sarcoma, Alveolar Soft Part;   Chordoma;   Epithelioid Sarcoma;   Giant Cell Tumor of Bone;   Hemangiopericytoma;   Gastrointestinal Stromal Tumor (GIST)
Intervention: Drug: Dasatinib
26 Active, not recruiting Sorafenib and Dacarbazine in Soft Tissue Sarcoma

Conditions: Sarcoma;   Synovial Sarcoma;   Leiomyosarcoma;   Malignant Peripheral Nerve Sheath Tumor
Intervention: Drug: Sorafenib and Dacarbazine
27 Recruiting Safety Study of PLX108-01 in Patients With Solid Tumors

Conditions: Solid Tumors;   Mucoepidermal Carcinoma (MEC) of the Salivary Gland;   Pigmented Villo-nodular Synovitis (PVNS);   Gastrointestinal Stromal Tumors (GIST);   Anaplastic Thyroid Carcinoma (ATC);   Solid Tumors With Documented Malignant Pleural or Peritoneal Effusions;   Malignant Peripheral Nerve Sheath Tumor (MPNST);   Neurofibromatosis Type I (NF-1);   Melanoma
Intervention: Drug: PLX3397
28 Active, not recruiting Depsipeptide (Romidepsin) in Treating Patients With Metastatic or Unresectable Soft Tissue Sarcoma

Conditions: Adult Alveolar Soft-part Sarcoma;   Adult Angiosarcoma;   Adult Epithelioid Sarcoma;   Adult Extraskeletal Chondrosarcoma;   Adult Extraskeletal Osteosarcoma;   Adult Fibrosarcoma;   Adult Leiomyosarcoma;   Adult Liposarcoma;   Adult Malignant Fibrous Histiocytoma;   Adult Malignant Hemangiopericytoma;   Adult Malignant Mesenchymoma;   Adult Neurofibrosarcoma;   Adult Rhabdomyosarcoma;   Adult Synovial Sarcoma;   Gastrointestinal Stromal Tumor;   Metastatic Ewing Sarcoma/Peripheral Primitive Neuroectodermal Tumor;   Recurrent Adult Soft Tissue Sarcoma;   Recurrent Ewing Sarcoma/Peripheral Primitive Neuroectodermal Tumor;   Stage III Adult Soft Tissue Sarcoma;   Stage IV Adult Soft Tissue Sarcoma
Intervention: Drug: romidepsin
29 Completed S0330 Erlotinib in Treating Patients With Unresectable or Metastatic Malignant Peripheral Nerve Sheath Tumor

Condition: Sarcoma
Intervention: Drug: erlotinib hydrochloride
30 Recruiting IMC-A12 and Doxorubicin Hydrochloride in Treating Patients With Unresectable, Locally Advanced, or Metastatic Soft Tissue Sarcoma

Conditions: Adult Angiosarcoma;   Adult Desmoplastic Small Round Cell Tumor;   Adult Epithelioid Sarcoma;   Adult Extraskeletal Chondrosarcoma;   Adult Extraskeletal Osteosarcoma;   Adult Fibrosarcoma;   Adult Leiomyosarcoma;   Adult Liposarcoma;   Adult Malignant Fibrous Histiocytoma of Bone;   Adult Malignant Hemangiopericytoma;   Adult Malignant Mesenchymoma;   Adult Neurofibrosarcoma;   Adult Rhabdomyosarcoma;   Adult Synovial Sarcoma;   Childhood Angiosarcoma;   Childhood Desmoplastic Small Round Cell Tumor;   Childhood Epithelioid Sarcoma;   Childhood Fibrosarcoma;   Childhood Leiomyosarcoma;   Childhood Liposarcoma;   Childhood Malignant Hemangiopericytoma;   Childhood Malignant Mesenchymoma;   Childhood Neurofibrosarcoma;   Childhood Synovial Sarcoma;   Dermatofibrosarcoma Protuberans;   Metastatic Childhood Soft Tissue Sarcoma;   Mixed Childhood Rhabdomyosarcoma;   Pleomorphic Childhood Rhabdomyosarcoma;   Previously Treated Childhood Rhabdomyosarcoma;   Previously Untreated Childhood Rhabdomyosarcoma;   Recurrent Adult Soft Tissue Sarcoma;   Recurrent Childhood Rhabdomyosarcoma;   Recurrent Childhood Soft Tissue Sarcoma;   Stage III Adult Soft Tissue Sarcoma;   Stage IV Adult Soft Tissue Sarcoma
Interventions: Biological: cixutumumab;   Drug: doxorubicin hydrochloride;   Other: laboratory biomarker analysis
31 Active, not recruiting Combination Chemotherapy in Treating Patients With Stage III or Stage IV Malignant Peripheral Nerve Sheath Tumors

Conditions: Neurofibromatosis Type 1;   Sarcoma
Interventions: Biological: filgrastim;   Drug: doxorubicin hydrochloride;   Drug: etoposide;   Drug: ifosfamide;   Procedure: conventional surgery;   Radiation: radiation therapy
32 Terminated Imatinib Mesylate Treatment of Patients With Malignant Peripheral Nerve Sheath Tumors

Condition: Malignant Peripheral Nerve Sheath Tumors
Intervention: Drug: imatinib mesylate
33 Recruiting Study of Everolimus With Bevacizumab to Treat Refractory Malignant Peripheral Nerve Sheath Tumors

Conditions: Malignant Peripheral Nerve Sheath Tumors;   MPNST;   Sarcoma
Interventions: Drug: everolimus;   Drug: bevacizumab
34 Recruiting Gemcitabine Hydrochloride With or Without Pazopanib Hydrochloride in Treating Patients With Refractory Soft Tissue Sarcoma

Conditions: Adult Alveolar Soft-part Sarcoma;   Adult Angiosarcoma;   Adult Desmoplastic Small Round Cell Tumor;   Adult Epithelioid Hemangioendothelioma;   Adult Epithelioid Sarcoma;   Adult Extraskeletal Chondrosarcoma;   Adult Extraskeletal Osteosarcoma;   Adult Fibrosarcoma;   Adult Leiomyosarcoma;   Adult Liposarcoma;   Adult Malignant Fibrous Histiocytoma;   Adult Malignant Hemangiopericytoma;   Adult Malignant Mesenchymoma;   Adult Neurofibrosarcoma;   Adult Rhabdomyosarcoma;   Adult Synovial Sarcoma;   Childhood Alveolar Soft-part Sarcoma;   Childhood Angiosarcoma;   Childhood Desmoplastic Small Round Cell Tumor;   Childhood Epithelioid Hemangioendothelioma;   Childhood Epithelioid Sarcoma;   Childhood Fibrosarcoma;   Childhood Leiomyosarcoma;   Childhood Liposarcoma;   Childhood Malignant Hemangiopericytoma;   Childhood Malignant Mesenchymoma;   Childhood Neurofibrosarcoma;   Childhood Synovial Sarcoma;   Dermatofibrosarcoma Protuberans;   Metastatic Childhood Soft Tissue Sarcoma;   Nonmetastatic Childhood Soft Tissue Sarcoma;   Recurrent Adult Soft Tissue Sarcoma;   Recurrent Childhood Soft Tissue Sarcoma;   Stage III Adult Soft Tissue Sarcoma;   Stage IV Adult Soft Tissue Sarcoma
Interventions: Drug: gemcitabine hydrochloride;   Drug: pazopanib hydrochloride;   Other: placebo;   Other: laboratory biomarker analysis
35 Recruiting Proton Therapy for Spinal Tumors

Conditions: Malignant Peripheral Nerve Sheath Tumors of the Spine;   Neurofibroma
Intervention: Radiation: Proton Therapy
36 Recruiting Natural History Study of Patients With Neurofibromatosis Type I

Conditions: Neurofibromatosis Type 1;   Malignant Peripheral Nerve Sheath Tumor;   Plexiform Neurofibroma;   Optic Glioma;   Neurofibroma
37 Completed Phase II Study of the Multichannel Auditory Brain Stem Implant for Deafness Following Surgery for Neurofibromatosis 2

Condition: Neurofibromatosis 2
Intervention: Device: Multichannel Auditory Brain Stem Implant
38 Completed An Implant for Hearing Loss Due to Removal of Neurofibromatosis 2 Tumors

Condition: Neurofibromatosis 2
Intervention: Device: Penetrating auditory brainstem implant
39 Suspended PTC299 for Treatment of Neurofibromatosis Type 2

Condition: Neurofibromatosis 2
Intervention: Drug: PTC299
40 Unknown  Sunitinib in Treating Patients With Recurrent or Unresectable Meningioma, Intracranial Hemangiopericytoma, or Intracranial Hemangioblastoma

Conditions: Brain and Central Nervous System Tumors;   Neurofibromatosis Type 1;   Neurofibromatosis Type 2;   Precancerous Condition
Intervention: Drug: sunitinib malate




Benign Intracranial Tumors Radiosurgery Treatment

Points to remember

  • Radiosurgery is focused delivery of radiation to an image-defined target performed in 1 to 5 sessions.
  • When used as an alternative to or in conjunction with open neurosurgical techniques, radiosurgery is an effective, less invasive option for treating many benign intracranial tumors, including meningiomas, vestibular schwannomas, and pituitary adenomas.

The challenge

Benign intracranial tumors occur about as often as primary malignant brain tumors. Most benign tumors are noninvasive, well defined and well visualized on MRI, and have a slow rate of progression. Each of these features makes them good candidates for radiosurgery.

Radiosurgery can deliver a destructive dose of radiation to the target with little or no radiation effects on adjacent structures. Proper patient selection for this procedure is critical.

Defining selection criteria

With 2 decades of experience performing radiosurgery, Mayo Clinic neurosurgeons have accumulated a depth of expertise and a vast database that includes patient characteristics, radiosurgical dosimetry, and outcomes.

After reviewing more than 1,400 cases of meningiomas, vestibular schwannomas, and pituitary adenomas, Mayo clinicians observe that radiosurgery is an excellent choice when these types of benign tumors are small, occur in critical locations, or have recurred following previous surgery.

Radiosurgery is also well tolerated and of particular utility in elderly patients with medical conditions that put them at risk for an open procedure. Additionally, radiosurgery does not preclude an open procedure, should that be necessary at a later time.

Radiosurgery for meningiomas

The rate of recurrence for a surgically removed meningioma is about 18% to 25% at 10 years. For this reason, Mayo neurosurgeons recommend maintaining extended surveillance of meningiomas. In contrast, radiosurgery has been found to reduce the risk of recurrence or progression.

Tumor progression outside the field of radiation and tumor histology can affect both long- and short-term outcomes. Tumors that can be clearly imaged and those that are benign and without atypical histology have a far greater rate of 5-year progression-free survival.

Radiosurgery is also an effective therapy for cavernous sinus meningiomas, except when there is symptomatic mass effect, an unusual clinical presentation, or nontypical features on imaging.

Radiosurgery is typically not recommended for convexity and parasagittal meningiomas.

Radiosurgery for vestibular schwannomas

Several studies report that radiosurgery for small to moderate-sized vestibular schwannomas is associated with higher rates of hearing preservation and improved facial nerve outcomes when compared to surgical removal. This conclusion was supported by a Mayo Clinic study comparing surgical resection and radiosurgery for vestibular schwannomas with an average diameter of less than 3 cm. These Mayo investigators also found that the radiosurgical patients experienced less postprocedure dizziness.

Image of MRI of patient's brain with parathyroid carcinoma before radiosurgery

MRI of patient’s brain with parathyroid carcinoma before radiosurgery


Image of MRI of patient's brain with parathyroid carcinoma 12 years after radiosurgery

MRI of patient’s brain with parathyroid carcinoma 12 years after radiosurgery


Radiosurgery for pituitary adenomas

Radiosurgery is considered safe and effective for hormone-secreting pituitary adenomas. When compared with radiotherapy, radiosurgery appears to shorten by more than half the time required to achieve biochemical remission and normal hormone levels.

Controversy remains over whether pituitary-suppressive medications at the time of surgery have a negative impact on tumor control. Several studies, however, including a series of 46 acromegaly cases at Mayo Clinic, found that patients were more than 4 times as likely to reach normal hormone levels if they were taken off such medications before surgery.

At Mayo Clinic, patients with oversecretion of growth hormone or adrenocorticotropic hormone and patients who experience new or progressing visual field deficits are referred for surgical resection. Patients with tumors that extend into the cavernous sinuses and patients with recurrent tumors after prior surgery, however, are generally treated with radiosurgery if the tumor does not directly involve the optic nerves and chiasm.

Across Mayo Clinic’s 3 sites in Arizona, Florida, and Minnesota, patients are seen by neurosurgeons with expertise in both open procedures and radiosurgery. When used as an alternative to or in conjunction with traditional neurosurgery, radiosurgery is an effective, noninvasive option for treating benign intracranial tumors.




Radiosurgery Treatment is  Radiotherapy in following versions:

  • single-session stereotactic radiosurgery,
  • fractionated conventional radiotherapy,
  • fractionated stereotactic radiotherapy, and
  • proton beam therapy.

Radiotherapy for vestibular schwannomas: a critical review.

Murphy ESSuh JH.


Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH 44195, USA. murphye3@ccf.org


Vestibular schwannomas are slow-growing tumors of the myelin-forming cells that cover cranial nerve VIII. The treatment options for patients with vestibular schwannoma include active observation, surgical management, and radiotherapy. However, the optimal treatment choice remains controversial. We have reviewed the available data and summarized the radiotherapeutic options, including single-session stereotactic radiosurgery, fractionated conventional radiotherapy, fractionated stereotactic radiotherapy, and proton beam therapy. The comparisons of the various radiotherapy modalities have been based on single-institution experiences, which have shown excellent tumor control rates of 91-100%. Both stereotactic radiosurgery and fractionated stereotactic radiotherapy have successfully improved cranial nerve V and VII preservation to >95%. The mixed data regarding the ideal hearing preservation therapy, inherent biases in patient selection, and differences in outcome analysis have made the comparison across radiotherapeutic modalities difficult. Early experience using proton therapy for vestibular schwannoma treatment demonstrated local control rates of 84-100% but disappointing hearing preservation rates of 33-42%. Efforts to improve radiotherapy delivery will focus on refined dosimetry with the goal of reducing the dose to the critical structures. As future randomized trials are unlikely, we suggest regimented pre- and post-treatment assessments, including validated evaluations of cranial nerves V, VII, and VIII, and quality of life assessments with long-term prospective follow-up. The results from such trials will enhance the understanding of therapy outcomes and improve our ability to inform patients.


Below, seminal papers on the subject

Meningioma of the internal auditory canal.

Laudadio PCanani FBCunsolo E.


Department of Otolaryngology–Head and Neck Surgery, Maggiore Hospital, Bologna, Italy.


A comprehensive literature search identified only 14 well-documented cases of intracanalicular meningioma. A case is presented of meningioma confined to the internal auditory canal which was excised using a sub-occipital retrosigmoid approach. Preoperative MRI and CT scans were suggestive of intracanalicular vestibular schwannoma. Only the intraoperative findings, which were confirmed by the histological data, revealed that the tumor was a meningioma. We review the literature and discuss the diagnostic and therapeuticissues relating to these tumors.

Facial nerve paralysis and meningioma of the internal auditory canal.

Hilton MPKaplan DMAng LChen JM.


Department of Otorhinolaryngology, Sunnybrook and Women’s College Health Science Centre, University of Toronto, Canada. malcolmhilton@hotmail.com


Pathological lesions confined to the internal auditory canal (IAC) commonly present with cochleovestibular symptoms; sensorineural hearing loss, tinnitus and balance disturbance. The commonest lesion of the IAC is vestibular schwannoma. Other lesions include meningioma, facial neuroma, cavernous haemangioma, lipoma and arachnoid cyst. Presentation with facial palsy and an intracanalicular lesion is suggestive of pathology other than acoustic neuroma. Magnetic resonance imaging (MRI) cannot reliably distinguish intracanalicular vestibular schwannomas from meningiomas. Particular care is required for surgery of these lesions: the facial nerve typically does not lie in a protected anterior position within the IAC.

Meningiomas of the internal auditory canal.

Nakamura MRoser FMirzai SMatthies CVorkapic PSamii M.


Department of Neurosurgery, Nordstadt Hospital, Teaching Hospital Hannover Medical School, Hannover, Germany. mnakamura@web.de



Meningiomas arising primarily within the internal auditory canal (IAC) are notably rare. By far the most common tumors that are encountered in this region are neuromas. We report a series of eight patients with meningiomas of the IAC, analyzing the clinical presentations, surgical management strategies, and clinical outcomes.


The charts of the patients, including histories and audiograms, imaging studies, surgical records, discharge letters, histological records, and follow-up records, were reviewed.


One thousand eight hundred meningiomas were operated on between 1978 and 2002 at the Neurosurgical Department of Nordstadt Hospital. Among them, there were 421 cerebellopontine angle meningiomas; 7 of these (1.7% of cerebellopontine angle meningiomas) were limited to the IAC. One additional patient underwent surgery at the Neurosurgical Department of the International Neuroscience Institute, where a total of 21 cerebellopontine angle meningiomas were treated surgically from 2001 to 2003. As a comparison, the incidence of intrameatal vestibular schwannomas during the same period, 1978 to 2002, was 168 of 2400 (7%). There were five women and three men, and the mean age was 49.3 years (range, 27-59 yr). Most patients had signs and symptoms of vestibulocochlear nerve disturbance at presentation. One patient had sought treatment previously for total hearing loss before surgery. No patient had a facial paresis at presentation. The neuroradiological workup revealed a homogeneously contrast-enhancing tumor on magnetic resonance imaging in all patients with hypointense or isointense signal intensity on T1- and T2-weighted images. Some intrameatal meningiomas showed broad attachment, and some showed a dural tail at the porus. In all patients, the tumor was removed through the lateral suboccipital retrosigmoid approach with drilling of the posterior wall of the IAC. Total removal was achieved in all cases. Severe infiltration of the facial and vestibulocochlear nerve was encountered in two patients. There was no operative mortality. Hearing was preserved in five of seven patients; one patient was deaf before surgery. Postoperative facial weakness was encountered temporarily in one patient.


Although intrameatal meningiomas are quite rare, they must be considered in the differential diagnosis of intrameatal mass lesions. The clinical symptoms are very similar to those of vestibular schwannomas. A radiological differentiation from vestibular schwannomas is not always possible. Surgical removal of intrameatal meningiomas should aim at wide excision, including involved dura and bone, to prevent recurrences. The variation in the anatomy of the faciocochlear nerve bundle in relation to the tumor has to be kept in mind, and preservation of these structures should be the goal in every case.

Surgical management of jugular foramen schwannomas with hearing and facial nerve function preservation: a series of 23 cases and review of the literature.

Sanna MBacciu AFalcioni MTaibah A.


Gruppo Otologico, Piacenza-Rome, Rome, Italy. mario.sanna@gruppotologico.it



Schwannomas of the jugular foramen are rare lesions and controversy regarding their management still exists. The objective of this retrospective study was to analyze the management and outcome in a series of 23 cases collected at a single center.


This study was conducted at a quaternary private otology and skull base center.


Charts belonging to patients with a diagnosis of jugular foramen schwannoma attending our center between May 1988 and April 2006 were examined retrospectively.


The study group consisted of 23 patients. One patient (a 73-year-old woman) with normal lower cranial nerves function was managed with watchful expectancy and regular clinical and radiologic follow ups. The infratemporal fossa approach-type A (IFTA-A) was performed in 3 cases. One patient underwent a transcochlear-transjugular approach. Of the 22 patients surgically treated, 12 patients were operated on by the petrooccipital transsigmoid approach (POTS). In one patient with a preoperative dead ear, a combined POTS-translabyrinthine approach was adopted. Two patients were operated on through the POTS approach combined with the transotic approach. In another case (a 67-year-old woman), a subtotal tumor removal through a transcervical approach was planned to resect a 10-cm mass in the neck. One patient underwent a first-stage combined transcervical-subtotal petrosectomy approach to remove a huge tumor in the neck; the second-stage intradural removal of the tumor was accomplished through a translabyrinthine-transsigmoid-transjugular approach. The last patient underwent a first-stage combined transcervical-subtotal petrosectomy approach to remove the neck tumor component; this patient is now waiting for the second-stage intradural removal of the tumor. Complete tumor removal was accomplished in 21 cases and in one case, a residual schwannoma was left in place in the area of the jugular foramen. The 3 patients who were operated on by IFTA-A underwent permanent anterior transposition of the facial nerve. At 1-year follow up, 2 of these patients had House-Brackmann grade I and 1 reached grade IV. The patient who underwent a transcochlear-transjugular approach had a permanent posterior transposition of the facial nerve. At 1-year follow up, he had grade III facial nerve function. Postoperative facial nerve function was normal (House-Brackmann grade I) in all patients operated on by the POTS approach. Twelve patients had hearing-preserving surgery using the POTS approach. Good hearing was preserved in 10 cases (83.3%), the majority of whom (58.3%) maintained their preoperative hearing level. There was no perioperative mortality. One patient (4.5%) experienced a postoperative cerebrospinal fluid leak. After surgery, all patients did not recover the function of the preoperatively paralyzed lower cranial nerves. A new deficit of one or more of the lower cranial nerves was recorded in 50% of cases. So far, no patient has experienced recurrence during the follow-up period as ascertained by computed tomography or magnetic resonance imaging.


Surgical resection is the treatment of choice for jugular foramen schwannomas. The POTS approach allowed single-stage, total tumor removal with preservation of the facial nerve and of the middle and inner ear functions in the majority of cases. Despite the advances in skull base surgery, new postoperative lower cranial nerve deficits still represent a challenge.

Meningiomas and schwannomas: molecular subgroup classification found by expression arrays.

Martinez-Glez VFranco-Hernandez CAlvarez LDe Campos JMIsla AVaquero JLassaletta LCasartelli CRey JA.


Unidad de Investigación, Hospital Universitario La Paz, 28046 Madrid, Spain. vmartinezg.hulp@salud.madrid.org


Microarray gene expression profiling is a high-throughput system used to identify differentially expressed genes and regulation patterns, and to discover new tumor markers. As the molecular pathogenesis of meningiomas and schwannomas, characterized by NF2 gene alterations, remains unclear and suitable molecular targets need to be identified, we used low density cDNA microarrays to establish expression patterns of 96 cancer-related genes on 23 schwannomas, 42 meningiomas and 3 normal cerebral meninges. We also performed a mutational analysis of the NF2 gene (PCR, dHPLC, Sequencing and MLPA), a search for 22q LOH and an analysis of gene silencing by promoter hypermethylation (MS-MLPA). Results showed a high frequency of NF2 gene mutations (40%), increased 22q LOH as aggressiveness increased, frequent losses and gains by MLPA in benign meningiomas, and gene expression silencing by hypermethylation. Array analysis showed decreased expression of 7 genes in meningiomas. Unsupervised analyses identified 2 molecular subgroups for both meningiomas and schwannomas showing 38 and 20 differentially expressed genes, respectively, and 19 genes differentially expressed between the two tumor types. These findings provide a molecular subgroup classification for meningiomas and schwannomas with possible implications for clinical practice.

Histological classification and molecular genetics of meningiomas.

Riemenschneider MJPerry AReifenberger G.


Department of Neuropathology, Heinrich-Heine-University, Duesseldorf, Germany.


Meningiomas account for up to 30% of all primary intracranial tumours. They are histologically classified according to the World Health Organization (WHO) classification of tumours of the nervous system. Most meningiomas are benign lesions of WHO grade I, whereas some meningioma variants correspond with WHO grades II and III and are associated with a higher risk of recurrence and shorter survival times. Mutations in the NF2 gene and loss of chromosome 22q are the most common genetic alterations associated with the initiation of meningiomas. With increase in tumour grade, additional progression-associated molecular aberrations can be found; however, most of the relevant genes are yet to be identified. High-throughput techniques of global genome and transcriptome analyses and new meningioma models provide increasing insight into meningioma biology and will help to identify common pathogenic pathways that may be targeted by new therapeutic approaches.

The neurofibromatosis type 2 gene is inactivated in schwannomas.

Twist ECRuttledge MHRousseau MSanson MPapi LMerel PDelattre OThomas GRouleau GA.


Centre for Research in Neuroscience, McGill University, Montreal, Canada.


Schwannomas are tumors arising from schwann cells surrounding peripheral nerves. Although most schwannomas are sporadic, they are seen in approximately 90% of individuals with neurofibromatosis type 2 (NF2), an autosomal dominantly inherited disease with an incidence of 1:40000 live births. The NF2 gene has recently been isolated on chromosome 22 and encodes a putative membrane organizing protein named schwannomin. It is believed to act as a tumor suppressor gene based on the high frequency of loss of heterozygosity (LOH) on this autosome in both sporadic and NF2 associated schwannomas and meningiomas and the identification of inactivating mutation in NF2 patients. In this study we examined 61 schwannomas including 48 sporadic schwannomas (46 of which are vestibular schwannomas) and 12 schwannomas obtained from NF2 patients, for mutations in 10 of the 16 coding exons of the NF2 gene. Twelve inactivating mutations were identified, 8 in sporadic tumours and 4 in tumors from people with NF2. These results support the hypothesis that loss of function of schwannomin is a frequent and fundamental event in the genesis of schwannomas.

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Reporter: Aviva Lev-Ari, PhD, RN
Just learned about that diagnosis given to a long time professional colleague. Started to research this topic and found an excellent clinical paper which I found appropriate for our Scientific Web Site – an Open Journal edifying the public on health related issues, BioMedical, Pharmaceutical and the Life Sciences.

Intracanalicular Meningioma Mimicking Vestibular Schwannoma

  1. Katsuyuki Asaokaa,
  2. David M. Barrsb,
  3. John H. Sampsonc,
  4. John T. McElveen Jrb,d,
  5. Debara L. Tuccid and
  6. Takanori Fukushimaa

+Author Affiliations


  1. athe Carolina Neuroscience Institute for Skull Base Surgery, Raleigh

  2. bthe Carolina Ear Research Institute, Raleigh

  3. cthe Division of Neurosurgery, Duke University Medical Center, Durham, NC

  4. dthe Division of Otolaryngology, Duke University Medical Center, Durham, NC
  1. Address reprint requests to Katsuyuki Asaoka, MD, PhD, Carolina Neuroscience Institute for Skull Base Surgery, 4030 Wake Forest Road, Suite 115, Raleigh, NC 27609


Summary: Three cases of intracanalicular meningioma mimicking vestibular schwannoma are presented. In each case, a contrast-enhancing mass filling the internal auditory canal was identified on MR images and was originally diagnosed as a vestibular schwannoma. Although it is difficult to differentiate definitively between these lesions preoperatively, imaging findings inconsistent with a diagnosis of vestibular schwannoma can be identified. Preoperative identification of intracanalicular meningiomas permits alterations in surgical planning that allow for the more complete resection of these rare tumors.


Meningiomas that occupy the cerebellopontine angle usually arise from the posterior surface of the petrous bone or the petrotentorial junction. Although, in some instances, a large cerebellopontine angle meningioma secondarily involves the internal auditory canal (IAC), meningiomas primarily arising from and mainly confined to the IAC are rare (110). We herein present three cases of intracanalicular meningioma, each with a different type of extracanalicular extension, that were initially suspected to be cases of vestibular schwannoma, and we discuss the diagnostic and therapeutic issues related to this disease entity.


Case Reports

Case 1

A 66-year-old man had a 3-month history of decreased hearing and high-pitched tinnitus in the left ear. He was seen by the local otologic service and the diagnosis of a vestibular schwannoma in the left IAC was made on the basis of MR imaging findings (Fig 1). He was referred to our institute for tumor resection. The preoperative audiologic examination showed that hearing on the left side was decreased to 50 dB pure tone average (500–3000 Hz), with a word recognition score of 56%. Because the patient’s hearing was still serviceable, we decided to use the middle fossa approach to attempt tumor eradication with hearing preservation. In the IAC, a tan, multilobulated, soft tumor with abundant vascularity was seen displacing the facial nerve posteriorly. The tumor did not appear to be a vestibular schwannoma and on frozen section was confirmed to be a meningioma. The tumor was meticulously dissected, with preservation of the facial and vestibulocochlear nerves. The origin of the tumor was the anterior wall of the IAC. The tumor, including the dural attachment, was totally removed. Postoperatively, the patient’s hearing worsened to a word recognition score of 20%, but the facial nerve function was normal. The final histologic examination revealed a meningioma with numerous psammoma bodies.


Fig 1.

FIG 1.

Case 1: 66-year-old man with an entirely intracanalicular meningioma. Contrast-enhanced axial T1-weighted MR image (450/14 [TR/TE]) reveals a homogeneously enhancing mass filling the IAC.


Case 2

A 39-year-old man noted a 1-year history of progressive decrease in hearing in his left ear, which had been of relatively sudden onset. He did not have tinnitus or dizziness. His MR images showed an enhancing mass occupying the left IAC and extending toward the petrous apex (Fig 2A and B). The preoperative audiogram showed a complete hearing loss in his left ear at 106 dB pure tone average. With a preoperative diagnosis of vestibular schwannoma, the tumor was removed by means of a translabyrinthine approach. Because of the anterior extension of the tumor, the facial nerve was completely skeletonized from the descending segment in the mastoid to the IAC. After incising the IAC dura, a friable, hypervascular tumor was exposed. The tumor entirely engulfed and was severely adherent to the facial nerve, with invasion into the anterior petrosal bone. A frozen histologic section showed a meningioma. The facial nerve was sharply dissected from the tumor and was rerouted inferiorly after cutting the greater superficial petrosal nerve. The invaded petrosal bone, including the cochlea, was extensively drilled away toward the petrous apex to totally remove the tumor. After surgery, mild left facial weakness (House-Brackmann grade III) was observed, which gradually returned to normal. The permanent pathologic specimen revealed a meningioma with tumor invasion into bone (Fig 2C). Immunohistochemistry showed that the tumor cells stained strongly for vimentin and did not stain for S-100 protein, features consistent with meningioma.


Fig 2.

FIG 2.

Case 2: 39-year-old man with an intracanalicular meningioma.


A, Contrast-enhanced axial T1-weighted MR image (540/12) shows an enhancing mass in the IAC extending toward the petrous apex and the cerebellopontine angle.


B, Contrast-enhanced coronal T1-weighted MR image (540/12) shows dural enhancement (arrow) in the IAC, which was noticed retrospectively.


C, Photomicrograph of specimen shows meningioma infiltrating into bone. (hematoxylin and eosin, original magnification ×100).


Case 3

A 67-year-old woman who had left hearing loss approximately 20 years previously gradually developed left facial weakness over a 2- to 3-year period. As a result, she underwent MR imaging that revealed an enhancing mass occupying the IAC and extending out to the porus acoustics (Fig 3) and was then referred to our institute with a diagnosis of vestibular schwannoma. Neurologic examination showed left facial weakness (House-Brackmann grade III) and left deafness. On the basis of our experience with the former two cases, we suspected a possibility of meningioma as a differential diagnosis because of the broad-based extension pattern of the tumor, which is unusual for vestibular schwannoma, and the association of facial weakness with a small intracanalicular tumor. The patient underwent surgery by means of translabyrinthine approach. The tumor was hypervascular and showed the typical appearance of meningioma under the operating microscope with numerous small calcifications. The frozen histologic section also revealed a meningioma. The origin of the tumor was the dura near the porus acoustics in the IAC. Because the tumor severely adhered to the facial nerve in the IAC, we had to leave a small amount of the tumor tissue on the nerve to avoid its damage. The histologic diagnosis was meningioma.


Fig 3.

FIG 3.

Case 3: 67-year-old woman with an intracanalicular meningioma. Contrast-enhanced axial T1-weighted MR image (600/9) shows an enhancing mass occupying the IAC and extending out to the cerebellopontine angle.



The development of high-spatial-resolution MR imaging has facilitated detection of small intracanalicular lesions. Although vestibular schwannomas account for most intracanalicular lesions, other, less common pathologic abnormalities including meningioma should always be considered, because they have implications for management strategy (11113). Intracanalicular meningioma, which originates from and mainly occupies the IAC, is a rare entity. To the best of our knowledge, 14 cases have been reported in the literature before our three cases. Eleven of 17 cases, including ours, were diagnosed by using contrast-enhanced MR imaging.


Origin of the Tumor

It is known that the origin of meningiomas is the arachnoid villi that are primarily found along major venous sinuses, especially around the superior sagittal sinus. Meticulous histologic study has shown that these arachnoid villi can also be within the IAC and could serve as a site of origin for intracanalicular meningiomas. Nager and Masica (14) found that arachnoid villi were distributed not only along the dural sinuses and in the gasserian envelopes but also along the greater superficial petrosal nerve, within the IAC, around the geniculate ganglion of the facial nerve, and within the jugular foramen. Guzowski et al (15) histologically examined 200 randomly selected temporal bones and confirmed the presence of arachnoid granulations around the petrous apex, near the trigeminal impression, and in the sulcus for the greater superficial petrosal nerve. Although they could not find true arachnoid granulations in the IAC, there were small clusters of arachnoid epithelium that could also serve as an origin of meningioma.


Diagnostic Considerations

It is difficult to differentiate small intracanalicular meningiomas from vestibular schwannomas preoperatively. The clinical symptoms caused by intracanalicular meningiomas are mostly identical to those caused by vestibular schwannomas and other lesions that occupy the IAC. Most of the cases initially manifest a hearing problem. The subtle difference is that facial nerve symptoms are more likely to occur with meningiomas than with vestibular schwannomas when the size is small. Four of 17 cases presented facial nerve symptoms, three with facial paralysis and one with hemifacial spasm, yet vestibular schwannomas of a similar size rarely cause facial paresis. Needless to say, the facial nerve schwannoma should also be considered when the patient presents with facial nerve symptoms.


Signal intensity of these masses on MR images will not contribute to the accurate radiographic diagnosis of the intracanalicular meningioma. Both lesions are isointense to hypointense on T1-weighted MR images and are of variable signal intensity on T2-weighted MR images. They will also both brightly enhance after administration of contrast medium. Vestibular schwannomas that originate from the IAC comprise approximately 90% of cerebellopontine angle tumors (16). In this context, when a patient is found to have an enhancing mass in the IAC, it is usually assumed to be a vestibular schwannoma. Most of the reported cases of intracanalicular meningiomas, including our three cases, were initially suspected to be vestibular schwannomas (3,510).


Nonetheless, there are some radiographic findings that should raise the suspicion of intracanalicular meningioma. Calcification and a “dural tail” may be helpful, although these findings are also nonspecific (117). In our second case, we retrospectively discovered intracanalicular dural enhancement in the coronal section of contrast-enhanced MR images. Another key is the extension pattern of the tumor. On the basis of the reported 17 cases, we categorized the extension patterns into following four types: 1) entirely intracanalicular (seven cases); 2) intracanalicular with cerebellopontine angle extension (five cases); 3) intracanalicular with both cerebellopontine angle extension and invasion into surrounding bone (three cases); and 4) intracanalicular with bone invasion but no cerebellopontine angle extension (two cases). Although it is very difficult to differentiate a meningioma from a vestibular schwannoma if an entirely intracanalicular type is encountered, other extension patterns may provide some information leading to the correct diagnosis. When the tumor extends out to the cerebellopontine angle, as in our third case, the growing pattern outside the IAC deserves attention. We think that broad-based extension into the petrous bone and a rugged medial tumor surface are valuable clues to the diagnosis of meningiomas, whereas vestibular schwannomas usually have a more spherical shape and have a smoother surface. Meningiomas in the IAC also have a tendency to involve adjacent nerve tissues or bones, (1279) as presented in our second case. Nager and Masica (14) showed, by histologic examination, that meningiomas located in the IAC can invade the labyrinth and cochlea by following their individual nerve fibers to their ends. Meningiomas can also infiltrate widely into surrounding petrous bone marrow spaces and air cells. Conversely, dilatation of the IAC due to bone erosion is a more common radiologic finding with vestibular schwannomas and extensive bone invasion is unusual. Thus, the presence of bone invasion around the IAC is suggestive the diagnosis of meningioma.


Therapeutic Issues

Preservation of facial nerve function is one of the most important issues in the surgery of intracanalicular lesions. It is important to note that the anatomic relationship between the tumor and the facial nerve in cases of intracanalicular meningioma is different from that in cases of vestibular schwannoma. With vestibular schwannoma, the facial nerve is compressed and classically displaced rostrally and medially by the tumor mass in the IAC. However, in our experience with these three cases of intracanalicular meningiomas, the tumor did not just compress the facial nerve but intimately involved it. Both in our second and third cases, the facial nerve was totally engulfed in the tumor. The adhesions between meningiomas and the facial nerve are also much more difficult to separate, even for smaller tumors, than those found in cases of vestibular schwannoma. Meticulous sharp dissection is very important to avoid damage to the facial nerve, even in cases of small intracanalicular meningiomas.



Complete resection of these tumors is important, because meningiomas are also more likely to recur than vestibular schwannomas. One of the reasons for this characteristic is considered to come from invasiveness into the adjacent structures, as mentioned above. Surgery of an intracanalicular meningioma, therefore, should be more extensive, resecting the tumor mass along with the attached dura and the invaded petrous bone. Because the preoperative differential diagnosis of intracanalicular lesions is usually difficult to make, intraoperative histologic diagnosis is essential. If meningioma is found, a more radical resection is accomplished to attempt to prevent recurrence. Preoperative suspicion of intracanalicular meningioma will assist the surgeon by allowing alterations in surgical planning that permit better exposure and more extensive resection of these difficult lesions.



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  • Received February 5, 2002.
  • Accepted after revision April 2, 2002.

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