[Posterior fossa microvascular decompression for hemifacial spasm and trigeminal neuralgia--some improvements on operative devices and technique].

Microvascular decompression has been widely used as a method for the treatment of hemifacial spasm and trigeminal neuralgia. We have experienced 30 such cases in the last 2 years; 25 of them were hemifacial spasm and 5 trigeminal neuralgia. Excellent results were obtained in 26 cases; the remaining two cases, both hemifacial spasm, were partially cured. Mild facial paresis appeared several days after the operation in 3 patients. In all the cases, the facial paresis recovered completely within several weeks. The cause of the facial paresis was not known. In 2 cases a slight hearing deficits were noticed after surgery, which has been gradually improving over several months. As this operation is functional surgery, operative complications must be avoided as much as possible. It has been our policy that we first try medical treatment and/or some kinds of nerve block and if no effects are obtained, we recommend the microvascular decompression. For microvascular decompression, suboccipital craniectomy is performed in lateral position. From the point of view of surgical technique, we stress several important points as follows: The head is elevated about 30 degrees, and it is kept approximately horizontal and should not be excessively rotated. Craniectomy is made as far laterally as the sigmoid sinus; its shape is elongated oval. Retraction of the cerebellum should not be done in the direction of the cranial nerves to avoid post-operative hearing deficit. Two tapered retractors are effectively used for cerebellar retraction. A third slim, tapered retractor is useful for holding an offending artery when exploring the root exit zone or placing a sponge for decompression.(ABSTRACT TRUNCATED AT 250 WORDS)