Arteries in contact with the cisternal portion of the facial nerve in autopsy cases: microsurgical anatomy for neurovascular decompression surgery of hemifacial spasm.

The cisternal portion of the facial nerve and its contact arteries were examined anatomically in relation to neurovascular decompression surgery to treat hemifacial spasm. Thirty-five sides of brains from 20 autopsied adult patients were examined under a surgical microscope (x 5-x 25). One attaching point was found on 10 facial nerves, two points on 20 nerves, and three points on four nerves. More than two thirds of the facial nerves were attached at two points: the root exit zone and the distal cisternal portion. In a case of distal attachment, the contact artery formed an arterial-nerve complex with the distal portions of the facial and acoustic nerves. The arterial attachment at the root exit zone was evident on 24 of the 35 facial nerves (69%), and most of the contact arteries were the anterior inferior cerebellar artery and its branches. In five nerves, the root exit zone was attached at two points to arteries. The anatomy of autopsied brains without hemifacial spasm is not identical to that of actual clinical cases of hemifacial spasm; nevertheless, the results do aid in intraoperative anatomical orientations.