The intrinsic vasculature of the cat facial nerve.

Treatment of facial nerve disorders is based in part on assumptions regarding the intrinsic blood supply of the nerve. This study was designed to comprehensively delineate the intrinsic facial nerve microcirculation and its relation to the extrinsic circulation in an animal model. Twenty-eight cat facial nerves were removed intact from brain stem to stylomastoid foramen following intravital fixation. Specimens were studied by gross dissection, silicone injection and tissue clearing, complete vessel counts on serial cross sections of individual nerves, and scanning electron microscopy or transmission electron microscopy. The labyrinthine segment of the cat facial nerve contains strikingly fewer intrinsic blood vessels than the mastoid and tympanic segments. The geniculate ganglion, however, has a distinct, rich vascular plexus. The ultrastructure of the intrinsic facial nerve vessels is similar to other small vessels of the body with tight junctions of the endothelium and overlapping spiral smooth muscle fibers of arterioles, as well as surrounding pericytes.