An acoustic neuroma is a benign tumor of the vestibular nerve that begins within the base of the skull and slowly expands into the skull cavity. The primary role of the vestibular nerve is to transform vestibular information (related to balance) into a frame of reference based on the position of the head in relation to the body. The vestibular nerve updates the frame of reference of motor movement based on the orientation of the head in relation to the body. As an example, when standing upright and facing forward, if you wished to tilt your head to the right you would need to perform a slight leftward motor movement (shifting more of your weight to your left side) to maintain balance. While the head is still in motion, the response magnitude of alteration to motor coordinates is significantly reduced when compared to when the head is fixated in one position.
The acoustic neuroma appears near the inner ear and their symptoms occur progressively in most patients. Some of these symptoms include slow and progressive destruction of hearing in the affected ear, a sense of imbalance and an altered gait, vertigo, nausea and vomiting. Interestingly, there is minimal or no tumor growth in some individuals.
If an acoustic neuroma does grow large enough, however, it can lead to increased intracranial pressure, which is associated with severe headaches and altered consciousness. The adjacent brainstem may also be compressed by these larger tumors, which affects a variety of local cranial nerves. The nearby facial nerve may also be affected. An acoustic neuroma that pushes against this nerve can lead to such symptoms as facial weakness and decreased facility of facial movements, facial numbness, sensory impairment, taste loss and the suppression of glandular secretions.
Peak incidence of acoustic neuromas occurs during the fifth and sixth decades of a patient’s life and both men and women are affected equally. In acoustic neuroma treatments, Gamma Knife radiosurgery has proven an exceptionally effective alternative to open surgery. Over the past 25 years, thousands of patients suffering from vestibular schwannomas have been successfully treated by means of the Gamma Knife and the results compare favorably with the published results of surgery.
While surgery is currently the only method of physically removing a vestibular schwannoma, it involves much higher risks than Gamma Knife procedures. In the treatment of acoustic neuromas, Gamma Knife surgery avoids the need for actual incisions. There is minimal discomfort and no post-treatment recovery period. While Gamma Knife treatments do not entail the physical removal of an acoustic neuroma, they do enable doctors to control, halt, and sometimes even reverse the growth of the tumor. With Gamma Knife, there is low risk of cranial nerve complications.