유돌분절에서 발견된 안면신경 이분지 1례

Recently, we have experienced a case of bifurcation of the facial nerve in mastoid segment during the middle ear surgery by accident. The patient was a 51 year-old female who had the symptoms of hearing impairment and intermittent otorrhea in left ear for 10 years. Temporal bone computed tomograph showed suspicious findings of bifurcated facial nerve in mastoid segment. In operative findings, outer branch of the bifurcated facial nerve proceded 5 mm from distal part of the 2nd genu and then rejoined with posteromedial curved branch of that at above the stylomastoid foramen. According to the reports, variations in the anatomic course of the facial nerve in mastoid segment are very rare. The type of anatomic variation in mastoid segment can be subdivided into three categories by Procter and Nager as followings.⁵⁾ The 1st type is slightly anteriorly, posteriorly curve when viewed laterally, medially or laterally curved when viewed behind. The 2nd type is a bifurcation or trif-urcation on posterior part of oval window or distal end and the 3rd type is hypoplasia of facial nerve. In order to avoid injury to the facial nerve, operator should check up the temporal bone CT findings thoroughly and keep variations of the facial nerve in mind during the middle ear surgery. (J Clinical Otolaryngol 2000;11:120–123)