Conditions: Acoustic Neuroma

What is an acoustic neuroma

What causes an acoustic neuroma?

An acoustic neuroma typically forms on one side or the other (about 95% of cases), and is due to random genetic changes that are usually not inherited. Less commonly, a specific inherited genetic condition called neurofibromatosis type 2 (now also called NF2-related schwannomatosis) is the cause of acoustic neuromas on both sides (bilateral) in the same individual. Neurofibromatosis type 2 causes tumors in nerves throughout the body, including within and directly under the skin, and can also lead to other tumors such as meningiomas, but in some cases, the diagnosis of neurofibromatosis type 2 is made only after the diagnosis of bilateral acoustic neuromas.

Acoustic neuroma and hearing loss, tinnitus, and facial weakness.

Due to its location, an acoustic neuroma can interfere with the function of the hearing, balance, and facial nerves on the affected side. Since this bundle of nerves passes through a bony canal (the internal auditory canal) that has little room to spare, a growth on the nerve within this canal can pinch the nerve fibers and their blood supply. Even though the tumor typically grows very slowly, loss of function of the facial and vestibulocochlear nerve may occur either gradually or suddenly, sometimes when the blood supply to the nerve becomes compromised. This may present as a change in hearing, an increase in tinnitus, or (less commonly) as a weakness of the facial muscles.

How is an acoustic neuroma diagnosed?

An acoustic neuroma is typically diagnosed based on radiologic imaging of the brain or part of the brain. Symptoms such as asymmetric sensorineural hearing loss, asymmetric tinnitus, or facial nerve weakness may be the impetus leading to obtaining imaging, or in other circumstances, imaging performed for another reason may incidentally demonstrate an acoustic neuroma. Magnetic Resonance (MR) imaging with a contrast dye (gadolinium) is the most accurate and detailed test to image an acoustic neuroma, but a large tumor may also be seen on a computed tomography (CT) scan.

How is an acoustic neuroma treated?

The treatment options for acoustic neuroma depend on several factors such as the size, location, and growth rate of the tumor, as well as your symptoms, hearing, age, and overall health. For small tumors that are not causing significant symptoms, the most common approach is observation (also called "wait and scan"), in which the tumor is monitored with regular MRI scans and treatment is started only if the tumor grows. When treatment is needed, the main options are radiation therapy (often a focused form called stereotactic radiosurgery), which uses precisely targeted radiation to stop the tumor from growing, and surgery to remove the tumor. Surgery is often recommended for larger tumors or those causing significant symptoms. The best option is chosen for each person and is often decided together with a team of specialists, which may include an ear surgeon, a neurosurgeon, and a radiation specialist.