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| NIH Consensus Statement on treatment of acoustic neuroma | ||
Here is the anatomy of the area where acoustic tumors occur.
Here is a picture of a large acoustic tumor
(the white shape toward the lower left, with the slight "tail" pointing toward the upper left).
| In our experience, the differential diagnosis of tumors in the area of the internal auditory canal of the temporal bone include the following: |
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| The alternatives are observation, radiation including gamma knife, and conventional microsurgery. |
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Observation
is indicated when there is a reasonable chance that the patient's life
expectancy is less than the length of time needed for the tumor to grow
to a life-threatening size, typically 4 cm in diameter or more.
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Radiation is indicated when a patient needs treatment, but has medical problems too severe to allow the patient to undergo surgery or if the patient refuses surgery (opinion of the National Institute of Health's Consensus Conference on acoustic tumors). This is consistent with published reports that support control of tumor growth for a period of one to three years after treatment. Longer follow up is not available. An attraction of radiation is an avoidance of the short-term morbidity and risk of mortality associated with surgery. However, the long-term morbidity and risk of mortality after radiation is comparable to the short-term risk of surgery. Many regional centers for the surgical treatment of acoustic tumors, such as ours, have lower complication rates than reported for radiation. Similar to surgery, the outcome following radiation is better with smaller tumors than with larger ones. Although some radiotherapists will treat all sizes of tumors, there is increased risk in radiating large tumors. Tumors often increase in size following radiation because of swelling. Tumor swelling may cause potentially life-threatening brain swelling and hydrocephalus. |
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| Microsurgery is the best choice for patients who need treatment. The alternative approaches are as follows: translabyrinthine, middle fossa, and suboccipital. |
| Translabyrinthine |
| Translabyrinthine is an approach through the mastoid and semicircular canals to the internal auditory canal. The advantages include the following. Few muscles are attached to the mastoid so that there is little muscle pain after surgery. There is an excellent view of the tumor in the internal canal. The surgical approach can be performed relatively quickly. There is little need for brain retraction. Disadvantages include the following. The exposure is relatively small. Removal of large tumors may take longer. Hearing preservation is difficult. Balance preservation is impossible. |
| Middle fossa |
| Middle fossa is an approach above the ear. The advantages include the following. There is an excellent view of the tumor in the internal canal. The chance of preserving hearing and possibly balance function in patients with tumors confined to the internal canal is as good as with any other approach. Disadvantages include the following. The temporalis muscle covering the bone flap is thin. Any irregularity in the bone flap may be felt as an annoying irregularity. The facial nerve often lies between the surgeon and the tumor. In these cases, the nerve must be retracted to remove the tumor. This puts the patient at greater risk of incurring a temporary facial muscle paresis after surgery. Removal of tumors extending beyond the internal canal is difficult because of limited exposure of the cerebellopontine angle. |
| Suboccipital |
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Suboccipital is an approach behind the mastoid. The advantages include the following. There is a large exposure of the cerebellopontine angle, an advantage for removing large tumors compressing the brainstem and cerebellum. The rate of hearing preservation for all sizes of tumor in our series is better than with any other approach. The rate of hearing preservation for tumors confined to the internal canal ranges from 65 to 85% (comparable to the best results reported for middle fossa surgery); tumors extending out of the canal but without brainstem compression from 25 to 45%; and tumors compressing the brainstem about 15% (largest tumor with hearing preservation is 3.5 cm). Proponents of translabyrinthine surgery state that facial nerve preservation is better with that approach; however, in our series facial nerve preservation is as good as with the translabyrinthine approach. We have been able to preserve the facial nerve in all patients with tumors less than 3 cm, and in 90% of patients with tumors 3 cm and larger. Disadvantages include the following. The cervical muscles must be separated from the subocciput to gain exposure. Muscle pain following surgery is common. One estimate is that 50% of patients will be experiencing headaches at six months after surgery, 25% at one year, and 10 to 15% at two years. Patients with muscle tension headaches prior to surgery are more likely to have headaches after surgery. |
| Antibiotic prophylaxis |
| Typically patients are given a dose of antibiotic just before surgery. The rationale follows below (reviewed in The Medical Letter on Drugs and Therapeutics Vol. 35, October 1, 1993). |
| Antistaphylococcal antibiotic |
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general terminology | complications | block terminology
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For information on support groups in Washington, and for connections to the national Acoustic Neuroma Association USA, click here. |
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