Acoustic neuroma, also known as “vestibular schwannoma,” is a tumor of 8th nerve which serves hearing and balance functions. The 8th nerve arises from the brainstem behind the ear. The tumor is considered benign and slow growing; however, it is in a dangerous part of the brain and its growth can be disabling and life limiting. National incidence is 1/100,000 and patients typically present after age 30 years.
The three most common early symptoms are hearing loss (slow and progressive), tinnitus (ringing in the ear), and disequilibrium. Sudden hearing loss occurs in 10% of cases. Other symptoms include headache, facial numbness/weakness, double vision, nausea/vomiting, otalgia (pain in the ear), and change in taste. Left untreated, the tumor can grow, compress the brainstem, and ultimately result in coma and death. Pregnancy can accelerate the growth of tumor.
Findings of cranial nerve dysfunction (CN 5-12) will depend on the size of the tumor. Findings of brainstem compression and increased intracranial pressure are more disturbing.
Magnetic resonance imaging (MRI) of the brain and internal auditory canal (w/wo contrast) will demonstrate the tumor and is the diagnostic exam of choice. Hearing exam and electronystagmography (ENG) are also performed.
Why does this occur?
Acoustic neuromas arise as a result of loss of a tumor-suppressor gene on the long arm of chromosome 22. In most cases this is a somatic mutation. In neurofibromatosis-2 (NF2) this is inherited and may be transmitted to children. Bilateral Acoustic neuroma is diagnostic of NF2 and any patient under 40 with unilateral Acoustic neuroma should be checked for NF2. Neurofibromatosis-1 (von Recklinghausen’s) will have unilateral Acoustic neuroma.
Recommended for elderly or sick patients with small tumors, and little to no symptoms. Serial MRI follow-up is advised and if tumor growth is relatively fast, surgery is advised.
Best performed by an experienced neurosurgeon and neuro-otologist team. Various approaches are available and choice depends on many factors including tumor size, location, and attempted hearing preservation. Surgery involves making a craniectomy (opening in the skull) behind the ear. The tumor is dissected off the nerves with the help of a microscope and nerve monitoring. The facial nerve (CN7) is usually draped over the tumor and can be thinned significantly. Saving CN7 can be a challenge with large tumors. Large tumors can parasitize the blood vessels from the brainstem forcing subtotal resection to avoid a stroke.
Stereotactic radiation (radiosurgery) can be done alone or after surgery. The dose of radiation rises significantly with the size of the tumor and can damage surrounding nerves. Outcome from radiosurgery alone is generally not as good as surgery. Radiosurgery is best used to treat residual tumor after surgery.
Outcome of Surgery
Size of tumor is the greatest determinant of outcome risk for hearing preservation and facial paralysis after surgery. Even if CN7 is anatomically preserved, temporary or permanent dysfunction may occur (mimicking Bell’s palsy). Permanent facial paralysis can be treated with plastic surgery for a satisfactory cosmetic result.
Local tumor control is the goal of surgery. Serial MRI follow-up is advised since 5% of treated cases can recur. Radiosurgery or repeat surgery for any recurrence may be needed.
We have the latest techniques and neurosurgical/neuro-otologic approaches available to us for your benefit. We take an aggressive approach to the treatment of acoustic neuromas. We have the clinical experience for great outcomes with a personal touch.