The Definitive Guide to Vestibular Schwannomas
Table of Contents
What is a Vestibular Schwannoma?
A vestibular schwannoma is also known as a neurilemmoma or a benign peripheral nerve sheath tumor. Although it is sometimes referred to as an acoustic neuroma, this is not technically correct as the tumor is not a neuroma. A neuroma is a disorganized growth of cells that occurs after a nerve has been cut or disrupted.
The non-cancerous tumor is caused by the overproduction of Schwann cells on the vestibulocochlear nerve, one of the cranial nerves. This is the main nerve from the inner ear to the brain. It is responsible for hearing (cochlear nerve) and balance (vestibular nerve). The Schwann cell’s role is to support and protect these nerves by forming sheaths around them.
Vestibular schwannomas account for 10% of brain tumors.
There are two types of vestibular schwannoma:
- Unilateral vestibular schwannomas occur in one ear, usually between the ages of 30 and 60. This is the most common type of vestibular schwannoma.
- Bilateral vestibular schwannomas occurs in both ears.
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Genetics of Vestibular Schwannoma
In most instances, a unilateral vestibular schwannoma occurs by chance and is a one-off single tumor, the causes of which are unknown.
The bilateral vestibular schwannoma (tumors affect both hearing nerves) is a characteristic of neurofibromatosis 2 (NF2), a disease of the nervous system that affects how nerve cells grow, causing tumors to grow on the nerves. Neurofibromatosis 2 can be inherited if one parent has the gene mutation.
It is extremely rare for a unilateral vestibular schwannoma to have been caused by an NF2 gene mutation.
Symptoms of Vestibular Schwannoma
A vestibular schwannoma can be challenging to diagnose due in part to its slow-growing nature. It can be several years before symptoms are experienced, and as a result, in most instances, the symptoms are very subtle.
Although the symptoms are generally related to hearing and balance, the tumor can also put pressure on the facial (CN VII) and trigeminal nerves (CN V), which control facial movement and sensation, respectively.
The most common symptoms of a vestibular schwannoma are as follows:
- Hearing loss, most commonly in the high-frequency range, in one ear
- Feeling of fullness in the ear
- Tinnitus or ringing in the ear
- Balance difficulties or unsteadiness on feet
- Clumsy gait
- Mental confusion
- Facial tingling and numbness (rare)
Diagnosis of Vestibular Schwannoma
Early diagnosis presents the best option for successful treatment; however, the location of vestibular schwannoma in the inner ear can make diagnosis difficult as other parts of the brain surround this area. The first steps in any diagnosis will typically involve an examination of the ear and hearing tests.
A computerized tomography (CT scan) or Magnetic Resonance Imaging (MRI scan) is often used to determine the location and size of any tumor. In some instances, a biopsy will be taken to confirm the diagnosis.
There are three options for treating a vestibular schwannoma.
- Surgical Removal
- Radiation Treatment
Observation is often recommended for small tumors that do not appear to be growing, where the patient is asymptomatic. Regular MRI scans typically do the monitoring.
The surgical removal of the tumor is dependent to a large degree on its location and size. There are several nerves and important brain structures within the face and skull, so as the tumor grows, it is likely to grow around these brain structures and nerves. This makes it harder to remove surgically because there is a risk of damaging the other nerves or brain parts. If the tumor is large, it is likely to have affected the nerves that control hearing, balance, and facial movement and sensation.
Radiation treatment is used to kill the tumor and prevent further growth and symptoms. This is often used in patients who may not withstand surgery due to poor health, elderly patients, patients with bilateral vestibular schwannoma, or patients where the tumor only affects hearing.
Gamma Knife Radiosurgery Treatment
Gamma knife radiosurgery treatment is also known as brain stereotactic radiosurgery. It is not surgery in the traditional sense as it does not involve cutting into the brain tissue. Specialized equipment is used to focus around 200 beams of targeted radiation directly to the vestibular schwannoma. The radiation has minimal effect on the other areas of the brain because it is precisely delivered to the point where the rays converge.
Gamma Knife radiosurgery has become the first-line treatment for small or medium size vestibular schwannomas. It is a safe and effective treatment option, with one study finding it stopped or shrunk the tumor in 97.1% of cases which is in effect a cure for vestibular schwannoma.
Gamma knife radiosurgery is a same-day treatment, completed as an outpatient, with most people experiencing no, or only minimal, side effects. The main benefits of Gamma Knife radiosurgery include it is virtually painless, and the patient can return to pre-treatment activities very soon after treatment.
The National Institute of Deafness and Other Communication Disorders (NIDCD) maintains a directory of organizations that provide further information regarding vestibular schwannoma and other conditions.
Research into vestibular schwannoma is ongoing, with scientists focusing on investigating gene therapies to control Schwann cells so they don’t produce tumors and robotic surgery technologies.
While hearing that you have any sort of brain tumor is a scary proposition for most people, a vestibular schwannoma has a low mortality rate. It can be treated effectively with relatively little discomfort to the patient. In most instances, treatment can alleviate the symptoms quickly and see the patient return to normal functioning.
Gamma Knife radiosurgery is one of the leading treatments and should be one of the things asked about when diagnosed with a vestibular schwannoma.
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