Clinic Anatomy Of The Glossopharyngeal Nerve And Its Abut Structures In Lateral Skull Base

The study were to obtain more useful detailed microanatomic information of the Glossopharyngeal nerve in the lateral skull base and the spatial relationships of surrounding structures, to provide some special information about the morphology and topography of the Glossopharyngeal Nerve (GphN) and its branches ,for the location and protection in surgery of lateral skull base.Methods1. Ten cadaver heads (20 sides) were used for microsurgical dissection , among these three heads injected with colored latex . Microsurgical anatomy and measurement were performed by lateraltranstemperal-sphenoid approach . Then exposed the whole length on the extracranial course of the GphN . During our dissection , the infratemporal fossa , parapharyngeal space , styloid diaphragm ?jugular foramen , the anatomic relationships of the muscles , arteries , veins and nerves were obtained .The greatest diameters of Glossopharyngeal Nerve (GphN )> Vagus Nerve , Accessory Nerve and Hypoglossal Nerve were measured . All stages of the dissections were photoghaphed .2. The distance between bony landmarks and foramina in the lateral skull base was determined through measurement of 30 (60 sides) dry adult skulls .Results1 , The glossopharyngeal nerve exits the skull through the jugular foramen posteromedial to the styloid process and the styloid muscle with Vagus Nerve and Accessory Nerves. The glossopharyngeal nerve can be easily separaed from the carotid sheath at the anterolateral surface .The inferior ganglion is formed near the jugular foramen by glossopharyngeal nerve . The tympanic branch (Jacobson's nerve) emerged from the inferior ganglion of the GphN and enters the middle ear through the tympanic canaliculus . A second small branch , this one to the carotid body , leaves Glossopharyngeal Nerve soon after it exits the skull .The last four cranial nerves and the internal jugular vein pass through a narrow space between the transverse process of the atlas(cl) and the sryloid process . Continuing inferiorly and anteriorly , the main trunk runs superficial to the internal carotid artery but deep to the jugular vein , external carotid artery , and styloid process to the deep surface of the stylopharyngeus muscle , which it innervates . The glossopharyngeal branch to the pharyngeal plexlus leaves the nerve trunk by the time it has crossed the stylopharyngeus muscle , and passes anteriorly and inferiorly between the internal and external carotid arteries to the main trunk to join branches of the Vagus Nerve and the cervical sympathetic nerves to form the pharyngeal plexus on the middle constrictor muscle at the level of the hyoid bone . Continuing , the main nerve trunk curves around the lateral border of the stylopharyngeus muscle , traveling toward the tongue base . Deep to the hyoglossus muscle , it divides into its terminal lingual and tonsillar branches .2. The distance from the midpoint of mastoid process and the angle of the mandible to the jugular foramen was 21.68 1.77 mm in left side and 21.44?.11 mm in the right side . We also measured the distance from the root of the sryloid process to the lateral border of the jugular foramen is 4.701.83 mm in the left and 3. 67 ?. 12 mm in the right ; to the lateral border of the carotid canal is 9.97 2.23 mm (left) and 10.03 + 1.74 mm (right) . The distance from the tip of the mastoid process to the lateral border of jugular foramen was 2 1.88 ?.20 mm (left) and 20.64?.00 mm (right) ; to the back border of the carotid canal is 30.68 2.43mm (left) and 30.97?.36 mm (right) .3. The styloid diaphragm devides the parapharyngeal space into prestyloid and retrostyloid regions and protects Internal Jugular Vein (IJV) , Internal Carotid Artery (1C A) and Glossopharyngeal Nerve, Vagus Nerve . Accessory Nerve and Hypoglossal Nerve .4. Glossopharyngeal Nerve crosses the deep surface of the stylopharyngeus muscle 23 to 47 mm cephalic to the bifurcation of the carotid artery and 7 to 15 mm from the tip of the styloid process . The greatest diameter of Glossopharyngeal Nerve was 1 .2 mm .