A rare variation of the glossopharyngeal nerve

The glossopharyngeal nerve (CN IX) provides innervation to the parotid gland, carotid body/sinus, mucosa of the middle ear, tongue and oropharynx and the stylopharyngeus muscle. The vagus nerve provides innervation to the remaining skeletal muscle of the pharynx. CN IX contributes to the pharyngeal plexus and normally provides innervation to the mucosa of the oropharynx. Herein, we describe a previously undescribed variation of CN IX. CN IX was observed to enter the pharyngeal wall but instead of forming terminal branches in the tonsillar fossa, CN IX descended along the posterior wall between the mucosa and pharyngeal constrictors to the esophagus. This unusual branch of CN IX gave rise to numerous branches along the pharynx but did not intermingle with laryngeal branches from the vagus nerve. From this dissection, we developed innervation maps of the pharynx and propose a central miswiring mechanism for this unusual variation.