Lingual distribution of the human glossopharyngeal nerve

Nineteenth century anatomical descriptions of the anterior distribution of cranial nerve (CN) IX on the dorsal tongue are contrary to current concepts. By employing Sihler's stain, we demonstrated that, in fact, CN IX projects more anteriorly than the posterior third of the tongue. This may explain why some patients whose chorda tympani branch of CN VII has been severed during middle ear surgery continue to have taste function in sectors of the anterior two-thirds of the tongue.

To assess the anatomical distribution of CN IX on the lingual dorsum.

Three human cadaver tongues were microdissected following staining with Sihler's stain, a procedure that renders most of the tongue tissue translucent while counterstaining nerves. CN IX nerve branches were visually tracked within the tongue's dorsum.

Branches of CN IX were observed that extended anteriorly beyond the sulcus terminalis and the circumvallate papillae, with extensions occurring along the lateral lingual margin anterior to the foliate papillae. Anastomoses were identified between CN IX and the lingual nerve, raising the possibility of functional interactions between CN V and CN IX.