Is Acoustic Neuroma A Brain Tumor?
Acoustic neuroma (AN) also known as vestibular schwannoma is a benign tumor arising from the cochlear part of the vestibulocochlear nerve which is the 8th cranial nerve. Acoustic neuroma is quite rare and approximately affects 1 in 100,000 persons in the population. Roughly about 2500 new cases of Acoustic neuroma are diagnosed each year and the incidence has increased in a recent couple of years. It is more common in women than in men and commonly seen in the age group of 30-60 years.
The vestibulocochlear nerve runs from the inner ear to the pons and it is responsible for hearing and equilibrium of the body. Acoustic neuroma arises from the Schwan cells which cover the nerve and it’s a slow-growing tumor. Since it arises from the 8th cranial nerve it is a benign brain tumor. It usually occurs in the internal auditory meatus and slowly grows and expands to the brain stem. The exact cause of Acoustic neuroma is not known, the only risk factor found so far associated with Acoustic neuroma is neurofibromatosis type 2 which is an autosomal dominant disease and accounts for about 5% of Acoustic neuroma cases. (3)
Can Acoustic Neuroma Cause Death?
Even though Acoustic neuroma is a slow-growing tumor with time it can expand and become a large tumor. Most patients are asymptomatic during the initial stages so until the tumor becomes large and compress the adjacent structures symptoms might not appear. Acoustic neuroma can cause some permanent damage and serious complications such as:
- Permanent hearing loss
- Difficulty in maintaining balance
- Facial weakness
- Continuous tinnitus
- Hydrocephalus (2)
Out of this hydrocephalus is serious and it occurs due to blockage of the cerebrospinal fluid flow by a large tumor. Hydrocephalus can increase the intracranial pressure which can damage the brain, lead to stroke, coma; brainstem herniation and death. The incidence of hydrocephalus due to Acoustic neuroma is quite rare. There is a case report of a 32-year-old woman presenting the emergency department with headache, nausea, and vomiting. She had a lesion in the cerebellopontine angle which was suspected as Acoustic neuroma. The initial CT scan revealed a 4th ventricle compression and hydrocephalus, a ventricular drain was inserted but the intracranial pressure remained high. The CT and MRI scan did after the procedure revealed brainstem herniation and brain infarction and brain death was confirmed. Therefore, identification of hydrocephalus and early treatment is needed.
Most of the mortality occurs during surgery or due to a complication of surgery. A nationwide study was done in the US to assess the morbidity and mortality rates following the operative excision of Acoustic neuroma tumors from 1994 through 2003. According to the results, 10,297 patients sought admission for Acoustic neuroma and out of those patients 4886 (47.5%) underwent retrosigmoid surgical excision and 75% of these lesions were large. The mortality rate following surgical excision was 0.5% (22 patients died) and the rate of adverse outcomes was 6.1% and the most common adverse outcome was facial nerve disorder which occurred in 25% of the patients. The in-hospital morbidity rate was 26.7%. Translabyrinthine surgical excision carries an intraoperative mortality rate 0-2% and the middle cranial fossa excision has a 0% mortality rate. (1) (4)
Acoustic neuroma is a benign type of a brain tumor arising from the cochlear parts of the vestibulocochlear nerve which is the 8th cranial nerve. Acoustic neuroma is quite rare and approximately affects 1 in 100,000 persons in the population. Acoustic neuroma arises from the Schwan cells which cover the nerve and it’s a slow-growing tumor and It usually occurs in the internal auditory meatus and slowly grows and expands to the brain stem. A patient can die if the Acoustic neuroma tumor becomes large and obstruct the cerebrospinal fluid flow causing hydrocephalus which leads to increased intracranial pressure, if not treated properly leads to herniation of the brainstem and death. However, hydrocephalus is a rare complication. More commonly patients die following surgical excision of Acoustic neuroma, the mortality rate is about 0.5% and the adverse outcome rate following surgery is 6.1%. Translabyrinthine surgical excision carries an intraoperative mortality rate 0-2% and the middle cranial fossa excision has a 0% mortality rate.
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