Acoustic Neuroma/Vestibular Schwannoma
Mount Sinai has made important contributions to the management of these benign tumors, which produce hearing loss, tinnitus, and dizziness. While surgery for acoustic neuromas may carry the risk of facial weakness and hearing loss, the majority of our patients experience no facial weakness or minimal temporary facial weakness. Similarly, hearing is preserved for a large percentage of patients, depending upon the preoperative hearing level and tumor size. Early diagnosis and treatment are critical to achieving excellent operative results, which Mount Sinai reports to be on par with few top institutions in the world.
About Acoustic Neuroma
Acoustic neuroma (vestibular schwannoma) is a benign tumor of the hearing and balance nerve that usually causes progressive hearing loss in one ear. Although it is an uncommon condition, in experienced hands a good outcome can be expected in most cases.
Acoustic neuromas are among the most common brain tumors. Nevertheless, their incidence is low, about 1 in 100,000, according to the National Cancer Institute. This works out to about 3,000 new cases of acoustic neuromas in the United States each year.
Diagnosis of Acoustic Neuroma
In most cases of acoustic neuroma, the chief complaint is hearing loss in one ear. Hearing loss tends to progress gradually, although sudden hearing loss is a possibility. Patients may also have trouble understanding phone conversations. Tinnitus (ringing in the ear) is also common, and tinnitus in one ear can be the first sign that something is wrong.
Not every patient with an acoustic neuroma has hearing loss, though. Some people maintain normal hearing even with large tumors. The degree of hearing loss does not depend on the size of the tumor.
Other symptoms of an acoustic neuroma include: balance problems, facial numbness or tingling, and other neurological problems, such as facial twitching, eyelid spasms and headaches.
Acoustic neuromas are usually discovered after abnormal hearing test (audiogram). An MRI will show the tumor. Other tests, including special hearing tests (ABR) and CT scans, may be recommended to develop a treatment plan.
Treatments for Acoustic Neuroma
The treatment of acoustic neuroma is individualized for each patient. The choice of treatment depends on several factors:
- Size of the tumor
- Symptoms and their duration
- Your age and health
Patients with newly discovered acoustic neuromas receive a full consultation with examination of the hearing, balance, and nerves. Special diagnostic tests of the hearing and balance systems are ordered when needed. Because we are a multi-disciplinary center specializing in the treatment of skull base tumors, consultations from our colleagues in neurosurgery and radiation therapy are usually obtained.
The treatment options for acoustic neuroma include:
- Serial observation: Because acoustic neuromas are usually slow growing tumors, we often recommend monitoring the tumor at regular intervals for signs of growth. For example in older patients, if the tumor is small it may never reach a size where it becomes life-threatening, and simple observation may be all the treatment that is needed. In properly selected patients, around 50 percent of tumors may remain stable in size and avoid the need for treatment with surgery or radiation.
- Surgical excision: Surgical removal of the tumor is the only treatment for acoustic neuroma that routinely results in cure. Recently, the techniques used in microsurgical treatment of acoustic neuromas have become quite advanced; the use of the microscope, microsurgical instruments, continuous facial nerve monitoring and stimulation, and continuous auditory monitoring have led to total cure with minimal risk for most patients. At Mount Sinai we have extensive experience with microsurgical removal using a team approach between neurosurgeon and neurotologist. We have achieved total tumor removal in almost every case. We preserve normal facial nerve function in the great majority of cases, and maintain hearing when the tumor is small, preoperative hearing is good, and ABR waveforms are present. The chance of tumor re-growth after complete microsurgical removal is extremely low. Surgical removal can be performed by a few different surgical approaches.
- Translabyrinthine surgery, in which the tumor is removed through the mastoid bone, behind the ear. This approach is appropriate for tumors with poor hearing status. The advantages are that this is a direct approach to the facial nerve, with minimal chance of brain swelling or postoperative headache.
- Retrosigmoid (suboccipital) approach, in which an opening is made in the skull behind the ear. This is appropriate for most large tumors, or small tumors where hearing preservation is a goal.
- Middle cranial fossa approach, in which small tumors are removed through an opening above the ear bone.
We use continuous electrical monitoring of the facial nerve during this surgery which, along with precise microsurgical dissection, has allowed us to preserve normal facial nerve function in most cases. When hearing preservation is a goal, we use continuous auditory evoked response monitoring during the surgery.
These surgical approaches have more similarities than differences, and the selection of the approach is largely a technical matter. Each route achieves excellent results. Our philosophy is to select the best approach for each patient, based on his or her age and health, tumor size, and hearing status.
- Stereotactic radiation: Acoustic neuromas can be treated by a specialized form of radiation, called stereotactic radiotherapy (“radiosurgery”). This treatment delivers a very high dose of radiation to the tumor, while avoiding spill-over to the sensitive tissues of the surrounding brain, nerves, and bone. In properly selected patients, radiotherapy is effective in controlling tumors about 90 percent of the time, with rapid recovery and return to work.