ABSTRACT
Background: Hypoglossal Nerve [HGN] is known to be a pure motor [General somatic efferent] cranial nerve
Objective: To confirm the existence, localization and morphology of the neurons contributing sympathetic fibers to the Hypoglossal nerve [HGN]. Material and Methods: This experimental animal study, was conducted in Basic Medical Sciences Institute, Jinnah Postgraduate Medical Centre, Karachi, from 1992 to 1995. Under general anesthesia the required hypoglossal nerves of twenty four albino rats were exposed and cut in the neck. Horseradish Peroxidase [HRP] crystals were applied to the central cut ends of the nerves and allowed to travel for about 48 hours. After transcardial fixation with 1.25% gluteraldehyde and 1% paraformaldehyde solution, serial sections of superior, middle and inferior cervical ganglia of both sides were made on a freezing microtome, treated with Tetramethylbenzidine [TMB] and counterstained by 1% neutral red. Labeled neurons were observed with the help of light microscope
Results: In all animals, the HRP labeled neurons contributing sympathetic fibers to the right and left hypoglossal nerves and their branches were located in the ipsilateral superior cervical ganglia only. Neurons were oval and rounded in shape, and randomly distributed in the ganglia. Average soma diameter of the neurons ranged between 6 to 38 microns
Conclusion: Hypoglossal nerve also contains sympathetic fibers which are contributed by ipsilateral superior cervical ganglion cells