Microvascular Decompression of a Facial Nerve in Hemifacial Spasm

Yu.A. Shulev, K.S. Gordienko

(Medical Academy of Postgraduate Education, Municipal Multi-Field Hospital N 2, Saint Petersburg)

The Study Goal. A neurovascular conflict is considered to be the most significant cause of hemifacial spasm (HFS). The study goal has been to estimate zones of a neurovascular conflict, which either cause or do not cause HFS.

Methods. The relationship between a facial nerve and adjacent vessels was studied in all 179 cases (98 females and 81 males; a mean age of 51.3 years), subjected to micovascular decompression. Trigeminal neuralgia and HFS were watched in 162 and 17 cases respectively.

We estimated three anatomic zones: a zone of a pontine-medullary fold and ventral segment of the pons (1); a cisternal segment of a facial nerve (2); an intrameatal segment of a facial nerve (3).

Results. Zones of a neurovascular conflict, located in a cisternal segment of a facial nerve, were revealed in 39 (24%) out of 162 cases with trigeminal neuralgia. Not a single case of this group had clinical manifestations of HFS.

There were 17 cases, operated for HFS; 14 of them (group I) had a conflict in a pontine-medullary fold zone (6) and in a zone of the pons ventral segment (8). Besides, 7 patient of group I demonstrated conflict zones in a cisternal segment. However, they turned out to be only an additional area of compression. Microvascular decompression in a cisternal segment, performed in 3 cases, had no positive effect. It was obtained after repeated operation with decompression in a zone of a pontine-medullary fold. Compression by a major vessel was diagnosed in 11 out of 14 cases of group I (basilar artery 9, vertebral artery 2, inferior posterior cerebellar artery (IPCA) 2, inferior anterior cerebellar artery (IACA) 1).

The IPCA loop was located in a meatal segment of the internal acoustic meatus in 3 cases with HFS. Meatotomy resulted in its displacement. Complete regression of hemispasm was observed in all cases.

Conclusions. A neurovascular conflict, watched in a mobile segment of a facial nerve (a cisternal segment), did not cause HFS. A major vessel, irritating the pons ventral segment (a zone of nuclei) and an area of the nerve exit from the pons, was a cause of HFS in 64.7% of cases. Operating patients with HFS, it is necessary to examine a pontine-medullary fold and the pons ventral surface. This examination can be given up only in cases with marked compression of the above nerve in a meatal segment of the internal acoustic meatus, caused by a major vessel (IPCA, IACA).