Ultrasound-guided vagus nerve block is useful in the management of the acute pain emergencies as an adjunct to pharmacologic, surgical, and antiblastic measures. In combination with glossopharyngeal nerve block, ultrasound-guided vagus nerve block is useful in the palliation of pain of malignant origin emanating from tumors of the posterior tongue, hypopharynx, and tonsils. This technique may also be utilized as a diagnostic maneuver when performing differential neural blockade on an anatomic basis when evaluating difficult-to-diagnose head and neck pain syndromes and when considering a diagnosis of vagal neuralgia. If destruction of the vagus nerve is being considered, this technique is useful as a prognostic indicator of the degree of motor and sensory impairment that the patient may experience. This technique may also be utilized to assist in localization of the vagus nerve when placing vagus nerve stimulator electrodes.

The key landmark when performing vagus nerve block is the styloid process of the temporal bone (Fig. 17.1). 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 vagus 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. 17.2). All three nerves lie in the groove between the internal jugular vein and internal carotid artery with vagus nerve lying caudad to the glossopharyngeal nerve with its downward course superficial to the jugular vein. The vagus nerve provides motor parasympathetic fibers to all organs below the neck except the adrenal glands. The nerve also provides motor innervation to the cricothyroid, levator veli palatini, salpingopharyngeus, palatoglossus, palatopharyngeus, superior, middle, and inferior pharyngeal constrictor muscles, as well as the muscles of the larynx. Although primarily a parasympathetic nerve, the vagus nerve also provides sympathetic innervation to peripheral chemoreceptors (Fig. 17.3).

To perform ultrasound-guided injection technique for vagus 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. 17.1). 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. 17.4).

The styloid process and the carotid artery and jugular vein are identified (Fig. 17.5). Color Doppler may be utilized to help confirm location of the vessels and their relationship to the styloid process (Fig. 17.6).