An acoustic neuroma or vestibular schwannoma, is a benign (non-cancerous) tumor that arises on the (8 th cranial) nerve. This is the nerve that affects your hearing and balance. Acoustic neuromas usually grow slowly over a period of years. They expand in size at their site of origin and when large can displace normal brain tissue. The brain is not invaded by the tumor, but the tumor pushes the brain as it enlarges.
The causes of an acoustic neuroma are unknown however research has shown that there are people with certain risk factors who are more likely to develop this condition over those outside of the risk factors. These risk factors include:
- Family history of neurofibromatosis
Early symptoms of acoustic neuromas include partial hearing loss or complete
hearing loss in one ear (this is usually subtle and worsens over time).
More than 80% of patients have reported ringing in the ears (tinnitus) described as high-pitched ringing, sometimes a machinery-like roaring
or hissing sound. Since the balance portion of the nerve is where the
tumor arises, unsteadiness and a disturbed sense of balance, and possibly
vertigo with associated nausea and vomiting may occur during the growth
of the tumor. Larger tumors can press on the
trigeminal nerve, causing facial numbness and tingling - constantly or intermittently. Tumor
related increase of intracranial pressure may cause headaches, clumsy
gait and mental confusion. This can be a life-threatening complication
requiring urgent treatment.
Even though the facial nerve (the nerve that moves the face) may be compressed by the tumor, it is unusual for patients to experience weakness or paralysis of the face from acoustic neuromas - although this may occasionally occur.
Diagnosis of an acoustic neuroma begins with a full medical history of the patient to rule out any other conditions. After medical history is collected a physical examination will be done which may include an audiogram to evaluate the hearing in both ears. A brainstem auditory evoked response test may also be performed. This hearing test measures your brain's response to clicking sounds in your ear. This test helps determine whether the eighth cranial nerve is working and if your hearing and brainstem are functioning properly. If an acoustic neuroma is suspected, an MRI or CT scan will be performed to confirm the presence of a neuroma.
Treatments for acoustic neuroma may include various options: physician monitored conservative treatment, surgical removal and radiotherapy. About 25% of all acoustic neuromas are treated with medical management consisting of a periodic monitoring of the patient's neurological status, serial imaging studies, and the use of hearing aids when appropriate. Choice of treatment are made by both the patient and physician and are dependent upon the size and location of the tumor, patient's age, symptoms, physical health and hearing. At SCCNS we encourage an open discussion with our patients as to their options and educate them on the risk associated with each treatment.
- Conservative Treatment: Because these tumors grow so slowly, a physician may opt for conservative treatment beginning with an observation period. In such a case, the tumor is monitored by annual MRI to monitor growth. This route is common among patients over 70 years old. Since the growth rate of an acoustic neuroma rarely accelerates, annual observation is sufficient.
- Surgical Treatment: Surgery may be necessary if the neuroma is affecting facial nerves, causing hearing loss or causing other problems. Removal of acoustic neuromas may be performed using several approaches. Each approach has its advantages and disadvantages. However surgery risks may include headaches, hearing loss, dizziness, and possibly facial weakness. Occasionally an additional surgery or stereotactic radiosurgery is needed to treat remaining tumor tissue. Acoustic neuroma surgery is highly technically demanding and should be performed by a neurosurgeon or otolaryngologist, alone or together.
- Stereotactic radiosurgery: Radiosurgery such as Gamma Knife uses beams of gamma radiation that are focused on the tumor in a single session. This treatment is designed to stop tumor growth. Regular follow up with your surgeon is necessary to check for any change in tumor growth. SCCNS is proud to offer this treatment at the Southern California Regional Gamma Center at San Antonio Community Hospital in Upland, CA.