An acoustic neruroma (also called a vestibular schwannoma) is a slow growing tumor that develops on the vestibulocochlear nerve, which is in charge of hearing and balance. This type of tumor is usually slow growing, and is seen more often in people with Neurofibromatosis Type 2 than in those with Type 1.
It is thought that acoustic neuromas develop from an overproduction of Schwann cells. Schwann cells help speed up how fast messages are sent along special nerve pathways in the brain. It is estimated that 5% of brain tumors caused by NF are acoustic neuromas.
Signs and Symptoms include:
- Hearing loss -- this is the most common symptom of acoustic neuromas, and is seen in approximately 90% of patients
- Tinnitus (ringing in the ears)
- Problems with balance
- Feelings of pressure inside the ear
- Facial weakness and numbness
The two most common tests used to diagnose acoustic neuromas are ear examinations and hearing tests. Usually the first test performed to diagnose an acoustic neruroma is an audiometry test, which is hearing test that measures how well a person can hear certain sounds. A patient listens to different sounds and speech and is attached to a machine that records the patients responses and measures hearing function. Another test that can be done is called a "brainstem auditory evoked response test", which provides information on a patients brainwave activity as they listen to different tones. While the patient listens to these different sounds, they have electrodes attached to their scalps, which help to pick up the brains responses to different sounds and tones.
MRI and CT scans can be used to determine the exact location of the tumor on the cranial nerve and the size of the tumor
The two primary treatments for acoustic neruromas are surgery and radiation therapy. These surgeries have some pretty funky names so I'll do my best to describe them for you!
1. Translabyrinthine -- an incision is made behind the ear, and the bone behind the ear and some of the middle ear is removed to access the tumor. This type of approach allows the doctor to see the facial nerve, but it unfortunately results in permanent hearing loss.
2. Retrosigmoid/sub-occipital --- the skull is opened near the back of the head. Typically this is used to remove larger tumors, and there is a greater likelihood that hearing would be preserved... Horray!
3. Middle fossa -- a small piece of bone is removed above the ear canal to access smaller tumors, hearing may also be preserved with this approach too!
Radiation therapy is usually used when surgery for whatever reason is not an option.
I hope you all learned something new this week, I know I sure did!