[Hemifacial spasm due to vascular compression of the distal portion of root exit zone of the facial nerve: report of two cases].

It has been generally assumed that only vascular contact at the root exit zone (REZ) of the facial nerve can cause hemifacial spasm. We treated two cases of hemifacial spasm in which compression of the distal site of the REZ of the facial nerve produced symptoms. The microvascular decompression for the patients showed excellent results. Extreme care must be taken not to stretch the internal auditory artery during surgical manipulation. The ABR monitoring is useful to prevent the postoperative hearing loss. It must be kept in mind that the compression of distal portions of the facial nerve may be responsible for hemifacial spasm in cases in which neurovascular compression at the REZ is not confirmed intraoperatively.