What causes acoustic neuromas and what is its growth pattern?
The cause of most acoustic neuromas is unknown.There is a small group of patients who have neurofibromatosis type 2, which is genetically determined. Acoustic Neuromas usually grow slowly over a period of many years. They characteristically remain within their lining (encapsulated) and displace normal tissue. The body accommodates to this abnormal growth. An acoustic neuroma first distorts the eighth nerve, then presses on the seventh nerve. The slowly enlarging tumor protrudes from the internal auditory canal into an area behind the temporal bone called the cerebellopontine angle. It now assumes a pear shape, with the small end in the canal. The tumor presses on adjacent nerves, such as the fifth, or trigeminal, which is the nerve of facial sensation. Ultimately, the tumor can press on the brainstem, which can be life threatening.
