Ultrasound-guided glossopharyngeal nerve block is useful in the management of the pain secondary to glossopharyngeal neuralgia as well as in the palliation of pain of malignant origin emanating from tumors of the posterior tongue, hypopharynx, and tonsils. This technique is also useful as an adjunct when performing awake intubation as well as to attenuate the gag reflex in posttonsillectomy patients and in those patients who are having difficulty tolerating an endotracheal tube during mechanical ventilation and during the weaning process from mechanical intubation when a decrease in sedation is desirable. Ultrasound-guided glossopharyngeal nerve block can also be used in a prognostic manner to determine the degree of neurologic impairment the patient will suffer when destruction of the glossopharyngeal nerve is being considered or when there is a possibility that the nerve may be sacrificed during surgeries in the anatomic region of the glossopharyngeal nerve. This technique may also be useful in those patients suffering symptoms from compromise of the glossopharyngeal nerve by an elongated styloid process and/or calcified stylohyoid ligament secondary to Eagle syndrome (see Chapter 15).

The key landmark when performing glossopharyngeal nerve block is the styloid process of the temporal bone (Fig. 16.1). The temporal styloid process extends from the temporal bone in a caudad and ventral direction and serves as the cephalad attachment of the stylohyoid ligament. The ligament attaches caudally to the hyoid bone. The glossopharyngeal nerve exits from the jugular foramen in proximity to the vagus and accessory nerve and the internal jugular vein and passes just inferior to the styloid process (Fig. 16.2). All three nerves lie in the groove between the internal jugular vein and internal carotid artery. The glossopharyngeal nerve (cranial nerve IX) contains both motor and sensory fibers (Fig. 16.3). The motor fibers innervate the stylopharyngeus muscle. The sensory portion of the nerve innervates the posterior third of the tongue, palatine tonsil, and the mucous membranes of the mouth and pharynx. Special visceral afferent sensory fibers transmit information from the taste buds of the posterior third of the tongue. Information from the carotid sinus and body that helps control blood pressure, pulse, and respiration is carried via the carotid sinus nerve, which is a branch of the glossopharyngeal nerve. Parasympathetic fibers pass via the

glossopharyngeal nerve to the otic ganglion. Postganglionic fibers from the ganglion carry secretory information to the parotid gland.

To perform ultrasound-guided injection technique for glossopharyngeal nerve block, place the patient in supine position with the head turned away from the side to be blocked. An imaginary line is drawn from the mastoid process to the angle of the mandible (see Fig. 16.1). In most patients, the styloid process lies just above the midpoint of this line. After preliminary identification of the approximate location of the styloid process, the skin is prepped with antiseptic solution, and 3 mL of local anesthetic is drawn up in a 10-mL sterile syringe, with 40 to 80 mg of depot steroid added if the condition being treated is thought to have an inflammatory component. A linear ultrasound transducer is then placed over the previously identified approximate location of the styloid process in the transverse plane (Fig. 16.4).