SURGICAL ANATOMY OF THE SINGULAR NERVE

Rare cases of chronic persistent positional vertigo do not respond to physiotherapy. For the treatment of these cases Gacek suggested singul ar nerve neurectomy as a new surgical procedure. The aim of the presen t study was to investigate the surgical anatomy of the singular nerve in order to evaluate the exact topography. In 25 cadaver temporal bone s the posterior ampullary (''singular'') nerve was prepared. The topog raphical correlation between singular nerve, posterior semicircular ca nal, and the round window membrane was evaluated. The average length o f the nerve was 4.2 mm, its diameter 0.6 mm. The shortest distance bet ween singular nerve and round window membrane was 0.7 mm in average, t he nerve could be detected at a depth of 1.3 mm. The transtympanal acc ess was impossible in 7 of 25 cases either because of its close relati on to the round window or its direct course towards the ampulla. In on ly 5 of 25 cases was the nerve located sufficiently inferior in the ro und window niche for neurectomy. Thus, transtympanal singular nerve ne urectomy can be performed only in selected cases. The presented data a re helpful for preoperative and intraoperative decisions.