An acoustic neuroma is a noncancerous (benign), often slow-growing tumor of the nerve that connects the ear to the brain. They usually grow slowly, gradually expanding the tunnel of bone (internal auditory canal), which houses the nerves that travel from the brainstem to the ear. As the tumors enlarge, they often protrude from the hole toward the brain, ultimately compressing the brainstem.
The symptoms vary based on the size of the tumor. Common symptoms include hearing loss in the affected ear, ringing in the ear (tinnitus), abnormal sensation of movement (vertigo) and occasionally dizziness and loss of balance. Pain is not usually a symptom of acoustic neuroma.
An MRI or CT scan usually identifies the acoustic neuroma. Frequently, it is discovered during an evaluation for hearing loss. Occasionally, a hearing test reveals the classical findings of sensory neural hearing loss. This type of hearing loss is related to the abnormal functioning of the hearing nerve (auditory nerve). Given the benign, non-cancerous and slow growing nature of these tumors, they are often discovered incidentally as part of a work-up for headaches or other neurologic symptoms.
Oftentimes the tumors are extremely slow-growing, and immediate treatment is not initially necessary. In certain cases, doctors may choose to perform follow-up MRI scans to evaluate for growth of the tumor. This is frequently the initial clinical approach to elderly patients who are found to have an acoustic neuroma. If the tumor is found to be growing, or if a tumor is found in a younger individual, then treatment is usually recommended. The two most common forms of treatment include surgery versus stereotactic radiosurgery. The goal of surgery is to remove as much of the tumor as possible as safely as possible, without injuring the facial nerve and causing facial paralysis. Tumors may be removed through a retromastoid approach, which involves making an opening in the back of the skull behind the ear. Another type of surgery involves a translabyrinthine approach, which involves approaching the tumor through the inner ear.
Stereotactic radiosurgery is a form of radiation therapy performed in a single sitting. The goal of radiosurgery is to slow or stop the tumor growth, not to cure or remove the tumor. Radiosurgery is limited to the treatment of acoustic neuromas which are less than 3 cm in size. Gamma Knife radiosurgery is the most precise form of radiosurgery and the most extensively-studied radiosurgical treatment of acoustic neuromas.
Both open microsurgery and stereotactic radiosurgery have associated risks and benefits, and the choice of treatment algorithm is made in conjunction with the patient, taking into account the patient’s age, size of the tumor, and symptoms. Many times patients may benefit from having both treatment modalities in a staged fashion.
An acoustic neuroma is not cancer. This tumor does not spread to other parts of the body, but it may continue to grow and press on important structures in the brain. With proper treatment, either surgery or stereotactic radiosurgery, patients are usually able to overcome the diagnosis of acoustic neuroma and lead a normal life.