GLOSSOPHARYNGEAL NERVE ANATOMY The glossopharyngeal nerve can be divided into three portions: cisternal, jugular foramen, and extracranial. Cisternal Portion The rootlets of the glossopharyngeal nerve originate from the upper part of the postolivary sulcus of the medul- la oblongata. These rootlets then usually form one root that courses forward and laterally on the anterior side ofthe flocculus and choroid plexus (Fig. 1). Its entrance por- us is separated from the entrance of the vagus and acces- sory nerves by a dural crest in the jugular foramen (Fig. 2). The mean length of the cisternal portion of the glos- sopharyngeal nerve is 15 mm. 40 The VA is located below and behind the jugular foramen. The PICA runs very close to the four lower cranial nerves, loops around the hypo- glossal nerve, and then courses along the fibers of the ac- cessory nerve (Figs. 1 and 3). The first landmarks of the glossopharyngeal nerve in the subarachnoid space are the flocculus and the chor- oid plexus of the lateral recess of the fourth ventricle. 40 The glossopharyngeal nerve may be compromised in this space by a vascular loop, a tortuous and ectatic basilar artery, an inflammatory process, a Chiari malformation, a neurenteric cyst, an exuberant choroid plexus, or a tu- mor. 7,8,16,21,22,25,29,31,33,38,48 These pathological processes may cause glossopharyngeal neuralgia, 7,25,31,38 paresis character- ized by dysphagia, loss of the gag reflex, or fullness in the pharynx. 8,27,30 They may also have a role in essential hy- pertension 29,33 and syncope attacks. 13,42 Exuberant choroid plexus tissue may become large enough to cause glos- sopharyngeal neuralgia. 38 The vessel that most common- ly causes glossopharyngeal neuralgia seems to be the PICA, 43 but the anterior inferior cerebellar artery can also compress the nerve. 13,30,31,42 In some cases, vascular cross- compression by adhesions between the PICA or the VA and rootlets of the glossopharyngeal nerve was a factor in essential hypertension and syncope attacks either with or without glossopharyngeal neuralgia. 13,29,33,42 Glossopharyngeal neuralgia is characterized by attacks of pain originating from the tonsil, tongue, or pharynx and radiating to the ear or the mandibular angle. 7 The par- oxysms are usually provoked by swallowing, especially of cold liquids, but coughing, sneezing, and touching the external meatus or ear lobe can also trigger pain. The pain may also begin in the ear and spread to the pharynx, which has led to a clinical distinction between the pharyn- geal and tympanic types of glossopharyngeal neuralgia. Some investigators have described a cardiovascular type in which the neuralgia is accompanied by bradycardia and arterial hypotension that causes syncope and con- vulsions. 7,13 Glossopharyngeal neuralgia is classically divided into primary and secondary groups. No cause can be demonstrated in the primary type, but it is believed that trauma, elongation of the styloid process, inflammation, tumors, and vascular deformities may cause the second- ary type. The glossopharyngeal nerve generally is easily recog- nized within the lateral cerebellomedullary cistern in both normal anatomical conditions and cases of vascular com- pression. If the subarachnoid space is filled with tumor tis- Neurosurg Focus 17 (2): E3, 2004, Click here to return to Table of Contents The microsurgical anatomy of the glossopharyngeal nerve with respect to the jugular foramen lesions MEHMET F AIK ÖZVEREN, M.D., AND UGUR TÜRE, M.D. Department of Neurosurgery, Firat University School of Medicine, Elazig; and Ondokuz Mayis University School of Medicine, Samsun, Turkey Removal of lesions involving the jugular foramen region requires detailed knowledge of the anatomy and anatom- ical landmarks of the related area, especially the lower cranial nerves. The glossopharyngeal nerve courses along the uppermost part of the jugular foramen and is well hidden in the deep layers of the neck, making this nerve is the most difficult one to identify during surgery. It may be involved in various pathological entities along its course. The glos- sopharyngeal nerve can also be compromised iatrogenically during the surgical treatment of such lesions. The authors define landmarks that can help identify this nerve during surgery and discuss the types of lesions that may involve each portion of the glossopharyngeal nerve. KEY WORDS • gl ossopharyngeal nerve • jugular foramen • lower cranial nerve • microsurgical anatomy Neurosurg. Focus / Volume 17 / August, 2004 12 Abbreviations used in this paper: CCA = common carotid artery; ECA = external CA; ICA = internal CA; IJV = internal jugular vein; OA = occipital artery; PICA = posterior inferior cerebellar artery; SCM = sternocleidomastoid; VA = vertebral artery.
