What is Acoustic Neuroma?
An acoustic neuroma is a tumour. In most cases, these tumors grow slowly over a period of years, but sometimes the rate of growth is more rapid. In a very small number of cases they can be cancerous. Sometimes they are referred to as ‘Acoustic Schwannomas’, ‘Vestibular Schwannomas’ or ‘Vestibular Neuromas’. Also known as the vestibulocochlear or eighth cranial the nerve runs from the brainstem to the inner ear and carries signals from the sounds we hear and also gives us the sensation of balance. They may present as sizable by the time that symptoms become apparent.
Radiosurgery for acoustic neuromas is well established and can be useful in the treatment of both unilateral and bilateral neuromas. Radiosurgery can be planned to try and preserve any residual hearing in the side being treated, although this is not always guaranteed. The choice of treatment may be based on tumour size, hearing in the ear at time of diagnosis, patient age and health, and patient preference.
What are the causes?
The cause of acoustic neuroma is not well understood however, it is currently thought that one-sided sporadic acoustic neuromas arise due to a spontaneous mutation (alteration in genetic material) on chromosome 22. This produces an overproduction of the Schwann cells and the formation of a lump, as they multiply producing a tumour filling the canal housing these nerves.
How common are neuromas?
The incidence is approximately 2 per 100,000 per year, accounting for 8 out of 100 cases of primary brain tumours. That equates to 1200 new diagnoses per year assuming a UK population of 60 million. Based on MRI studies, the true prevalence may be around 0.05% (1 in 200) of the population, which equates to 30,000 people, also assuming a UK population of 60 million. They have an increasing incidence with age, and are often found more commonly in women.
Diagnosing acoustic neuromas
The diagnosis of this condition is made after the patient reports symptoms. There is then a careful examination of the ear and the hearing and balance systems, along with a complete neurological examination and then sophisticated audiometry to test the hearing along with a clinical balance assessment. An MRI scan is used to make the final diagnosis and this is the gold standard diagnostic test.
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