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Acoustic NeuromaThe acoustic nerve lies deep within the skull base and connects the inner ear to the brainstem. This area of the brain controls heart rate, blood pressure and breathing functions. The hearing and balance portions of the nerve are intertwined as they exit the brainstem, then split into their respective divisions as the enter the inner ear through a bony channel called the internal auditory canal.
Acoustic neuromas comprise approximately six percent of all tumors which arise inside the skull. Approximately 2,500 new cases are diagnosed per year in the U.S. Recent studies have shown that these tumors commonly grow at a rate of 1/10 of an inch per year, although some may grow over 1/2 inch per year. As the tumor grows, it causes pressure on the surrounding structures, causing symptoms such as inner ear problems, especially involving only one ear. Since hearing loss is the initial symptom in the majority of patients, a complete hearing evaluation in a sound-proof booth is usually the first test obtained to screen for these tumors. Hearing loss in acoustic neuroma occurs on the side of the tumor and usually involves higher frequencies or higher-pitched sounds. Other symptoms include:
Microsurgical RemovalThe only treatment currently available to cure these tumors is complete removal through microsurgery. Significant advancements have been made in the last 30 years. Total tumor removal can be accomplished by one of several surgical approaches. The recommended approach is dependent upon the exact location and size of the tumor, as well as a determination of whether an attempt to preserve residual hearing is warranted. Partial or incomplete removal of an acoustic neuroma may be necessary under certain circumstances with the understanding that further surgery may be needed in the future. Prevention of further deterioration is the goal of surgery, and the residual tumor may not grow enough in the patient's lifetime to cause further problems. Follow-up MRI scans are used to detect any future growth. Among the microsurgical techniques used are:Translabyrinthine removal: the bone directly behind the ear (mastoid bone) is removed to expose the inner ear structures which are also removed. The internal auditory canal is exposed along its entire length and is then opened to remove the tumor. By removing the inner ear, all residual hearing is lost; thus this approach is used only when the hearing loss is already severe or if hearing preservation is not realistic. Retrosigmoid removal: the bone behind the mastoid and inner ear is removed to expose the tumor and the posterior aspect of the internal auditory canal. The back wall of the canal is removed to allow access to this portion of the tumor. This method can allow for hearing preservation in certain cases and may be used for small and large tumors. Middle fossa removal: this method is reserved for small tumors with good residual hearing that is salvageable. Bone is removed above the ear to expose the top of the inner ear and internal auditory canal, allowing access to the tumor. Patients who undergo surgical removal of their acoustic neuroma are generally hospitalized for five to seven days. Patients are generally advised to remain off work for a minimum of four to six weeks or longer, depending on their occupation. Stereotactic Radiation Therapy (Radiosurgery)A single large dose of radiation is delivered to the tumor in a single session. The radiation dose is delivered precisely to the tumor in an attempt to arrest growth while minimizing injury to the surrounding nerves or brain. Two sources or stereotactic radiation exist: radioactive cobalt (gamma knife) and linear accelerator. Either can deliver a precise dose of the radiation to the tumor. Radiation therapy does not kill or injure tumor cells immediately following treatment. The goal of radiation therapy is to arrest the growth or shrink the tumor, not cause complete disappearance. Some tumor cells are destroyed in a manner or weeks, while others die gradually over a period extending up to 18 months. With stereotactic radiation, patients often return home several hours after treatment and may return to work in several days. In the case of either microsurgery or stereotactic radiation therapy, the patient's doctor provides full information about any post-procedure problems. Support GroupsSupport groups consisting of other patients who have been diagnosed with acoustic neuroma can be helpful. For further information about a support group in your area, contact: The Acoustic Neuroma Association
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An acoustic neuroma is a non-cancerous tumor that originates from the nerves of
hearing (cochlear nerve) and balance (vestibular nerve). There are 12 cranial nerves that exit each side of the brainstem and serve
various function. The acoustic nerve is a combination of the cochlear and vestibular nerves, and is the eighth of the 12 cranial
nerves.