Ear Tumour : Acoustic Neuroma
The nervous system consists of the brain and the spinal cord. There are 12 pairs of nerves which arise directly from the brain and pass through openings in the skull to reach their locations. These are called the cranial nerves.
The eighth cranial nerve (properly known as the ‘vestibulocochlear’ nerve) is the one which serves hearing and balance. It is really in two parts: one part of the nerve is associated with transmitting sound information and the other with sending balance information to the brain from the hearing and balance organs located within the inner ear.
An acoustic neuroma is a benign (non-cancerous) growth that arises from the sheath surrounding the eighth cranial nerve.
Acoustic neuromas occur in conjunction with a fairly rare hereditary condition called neurofibromatosis 2, in which multiple cranial nerve tumours arise.
Acoustic neuroma is diagnosed only once per year per 100,000 people so from that point of view it is uncommon. However small acoustic neuromas, not causing any symptoms, can be found in up to nearly 3 per cent of elderly people. There is no known cause for these tumours, other than the hereditary type.
Acoustic neuromas usually grow slowly over a period of years and when large may press on normal brain tissue. Larger tumours can press on another nerve in the same area (the fifth cranial nerve or ‘trigeminal’ nerve) which is the nerve concerned with facial sensation.