Bifurcation of the Facial Nerve

GROSS ABNORMALITIES of the facial nerve in the temporal bone are rare, but they occur with sufficient frequency that the otologic surgeon must be mindful of their possibility. In the past, mastoid operations for suppurative disease drew attention to intraosseous aberrations in the vertical segment of the nerve's course. These have been well documented.1-9An increasing number of reconstructive middle ear operations with the operating microscope require that middle ear facial nerve anomalies be equally well recognized. Normal Anatomy of the Intratemporal Part of the Facial Nerve According to Anson,8the nervus intermedius (of Wrisberg) and the motor root of the facial nerve enter the opening of the facial canal (aqueductus falopii) in the fundus of the internal auditory meatus. The composite nerve passes laterally between the cochlea and the semicircular canals, toward the medial wall of the middle ear. It bends suddenly backward and runs in that