An acoustic neuroma is a tumor in the lining of the nerve that connects the inner ear with the brain. On the basis of each patient’s individual needs, the neurosurgeons at Columbia’s Skull Base Tumor Center choose among the treatment options: observation, stereotactic radiotherapy or surgical removal.
Acoustic neuromas are benign tumors, and most grow very slowly. Since they are benign, acoustic neuromas do not invade nearby tissue or spread elsewhere in the body. However, depending on their size and location, they have the potential to cause severe symptoms.
Acoustic neuromas arise in the lining of the eighth cranial nerve. This nerve carries information about hearing and balance, and the tumor can disrupt the transmission of this information. The tumor may also interfere with the seventh cranial nerve, which controls facial muscles and runs alongside the eighth cranial nerve through a small bony channel. Most acoustic neuromas begin growing inside this channel, and a growing tumor may compress the seventh cranial nerve against the bony walls.
Medium- and large-sized acoustic neuromas expand out of the bony channel. The end of the tumor free of the channel can grow larger than the end inside the channel, so such tumors have a pear shape. The larger end of the “pear” may compress the trigeminal nerve, causing facial pain. It may also compress the brainstem and cerebellum, causing hydrocephalus or interfering with vital functions.
Acoustic neuromas are also known as acoustic neurinomas or vestibular schwannomas.
Exact symptoms vary depending on a tumor’s size and location. An acoustic neuroma may cause:
- Hearing loss, especially on one side; this is by far the most common symptom of acoustic neuroma
- Loss of balance
- Facial numbness
To diagnose an acoustic neuroma, a doctor will first take a medical history and conduct a neurological exam. The doctor may order or conduct a hearing test. If symptoms and results are suspicious for an acoustic neuroma, the doctor may order an imaging scan.
The scan that allows the most accurate diagnosis of acoustic neuroma is an MRI with gadolinium contrast enhancement. An MRI uses magnets, radio waves, and a computer to create images of soft tissues such as nerves and tumors. Contrast enhancement is the injection of a dye (in this case, gadolinium) that makes even small amounts of tumor tissue stand out more clearly on the scan.
Most acoustic neuromas are not associated with any known risk factors.
Researchers have identified only one environmental risk factor for acoustic neuromas: exposure to ionizing radiation. This type of radiation is found naturally in the environment, as well as in X-rays and CT scans. It is not produced by microwaves or cell phones. However, exposure to ionizing radiation is not a factor in most cases of acoustic neuroma.
About 5% of acoustic neuromas are caused by a rare inherited condition called neurofibromatosis 2, or NF2. Though most patients with acoustic neuroma develop only one tumor, individuals with NF2 are likely to develop acoustic neuromas on both sides, and may develop other tumors as well.
Various treatment options exist for acoustic neuroma. Our neurosurgeons can help patients decide on the best treatment plan on an individual basis: observation, stereotactic radiotherapy, or surgical removal.
Observation may be appropriate for small tumors that don’t cause symptoms. Patients and surgeons may also choose observation when the patient’s age or general health increases the risks of surgery.
Stereotactic radiosurgery may be appropriate for some tumors. This treatment uses highly focused beams of radiation to disrupt the tumor’s growth. Unlike conventional surgery, it does not require an incision, and patients are generally able to return to normal life quickly after the procedure. However, it may take months or years to see the full effect of radiosurgery. Regular follow-up scans are required.
Surgical removal is necessary in some cases. The goals of surgery are to prevent or relieve compression of the brainstem or cerebellum, to remove as much tumor as possible, to preserve hearing when possible and to preserve facial nerve function when possible. Our surgeons are experienced with several different surgical approaches, each of which has its own set of risks and benefits. When weighing surgical approaches, a neurosurgeon considers the tumor’s size and location, a patient’s general health and current symptoms, individual variations in blood flow and anatomy of the inner ear, and a patient’s treatment priorities.
Our experienced neurosurgeons can help you weigh the risks and benefits of all treatment options.