Trajectory of the hypoglossal nerve in the hypoglossal canal: significance for the transcondylar approach.

A microanatomical study of the hypoglossal canal and its surrounding area was carried out using dry skulls and cadaveric heads to determine the course of the hypoglossal nerve in the hypoglossal canal, especially the significance for the transcondylar approach. The hypoglossal nerve enters the superomedial part of the hypoglossal canal as two bundles, which then change course abruptly to an anterosuperior direction, and unite as one trunk before exiting the canal. The hypoglossal nerve has an oblique course in the canal rather than being located in the center, and exits through the inferolateral part of the canal. A venous plexus surrounds the entire length of the nerve bundles in the canal. The present results suggest that during drilling the occipital condyle toward the hypoglossal canal from behind, the surgeon does not need to be overly concerned even if some bleeding occurs from the posterolateral edge of the hypoglossal canal.