The trigeminal sensory innervation to the middle ear, eustachian tube, and pharynx: a study by the horseradish peroxidase tracer method.

The trigeminal sensory innervations to the middle ear, the eustachian tube, and the pharynx were examined using the horseradish peroxidase (HRP) method in cats. After HRP application to the middle ear and the eustachian tube, HRP-labeled cells were found mainly in the posterolateral portion and the anteromedial portion of the trigeminal ganglion, respectively. In the case of injection into the epipharynx and the mesopharynx, HRP-labeled cells were found in the anteromedial portion and the posterolateral portion, respectively. HRP-labeled cells were hardly observed when HRP was applied to the hypopharynx. These results indicate that trigeminal nerve sensory fibers branch to the middle ear, including the eustachian tube, epipharynx, and mesopharynx.