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Total Microsurgical Removal
At this time, the only treatment that can cure the patient with an acoustic neuroma is microsurgical removal. Within the last three decades, microsurgical techniques have been refined so that the risk of total tumor removal has been greatly reduced. Microsurgical instruments and the operating microscope are routinely employed. Damage to the surrounding nerve tissue has been markedly decreased and the mortality rate is extremely low.
Facial nerve function is routinely monitored during surgery, which has reduced the frequency and severity of facial nerve injury. Cochlear nerve monitoring is also employed during surgery where it appears feasible to preserve hearing. According to the 1991 NIH Consensus Statement, "the best published surgical outcomes in the treatment of vestibular schwannoma are from medical centers that have highly organized an dedicated teams with a specific interest in these tumors and sufficient continuing experience to develop, refine, and maintain proficiency. Our specially trained audiologists participate in the surgery by monitoring facial function and hearing.
There are several surgical approaches which may be used to remove an acoustic tumor. The route depends upon the location and size of the tumor, as well as the presence of residual hearing.
Middle Fossa Approach
In this approach, the bone is opened above the ear and the bone overlying the tumor is removed. The middle fossa approach may be selected for small tumors with good hearing. This approach is usually limited to tumors that extend out of the internal auditory canal no further than one centimeter toward the brainstem.
Retrosigmoid Approach
In this approach, the bone is opened behind the mastoid and inner ear and the tumor is approached from behind. This approach also allows the possibility of hearing preservation and may be used for both small and large tumors.
Translabyrinthine Approach
In the translabyrinthine approach, the incision is located behind the ear and the mastoid bone is removed. This approach involves removing the inner ear structures, and thus destroys hearing. It is, therefore, used only for those cases where hearing loss is already severe or the tumor is so large that hearing conservation is not a realistic goal.
Regardless of the approach, the patient is observed in the intensive care unit for one or two days with careful monitoring. Headache, nausea, vomiting, and decreased mental alertness may occur regardless of the surgical approach. Other postoperative problems include cerebrospinal fluid leak and meningitis. The cerebrospinal fluid leak may be treated by drainage of the spinal fluid through the lower back, or in rare cases, secondary surgery. Meningitis is an infection in the fluid surrounding the brain and is treated with antibiotics.
Each of the surgical approaches has advantages and disadvantages. Excellent results have been achieved using each of the above approaches. This decision is individually based on patient preferences, hearing capabilities and tumor characteristics.
Hospital stay after microsurgery ranges from 4-7 days with approximately 4 weeks suggested for recovery. Regrowth rates after microsurgery are less than 5%.
Partial Microsurgical Removal
Incomplete removal of an acoustic neuroma is elected by some patients and their surgeons in order to reduce the risk of complication with the realization that further surgery may be needed in the future. Occasionally, because of disturbances of the patient's vital brain centers during surgery, the operation is terminated before the tumor is totally removed. In that case, the residual tumor is followed with MRI scans and, if tumor growth is shown, further surgery to totally remove the tumor may be necessary. On the other hand, if the tumor shows no growth, continued observation can take place.
Partial tumor removal has been advocated in some patients who have a tumor in their only hearing ear. This is primarily in patients who have Neurofibromatosis Type 2. Unfortunately, partial removal may result in substantial hearing loss in these patients and this risk must be considered.
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