Ultrasound-guided auriculotemporal nerve block is useful in the diagnosis and treatment of a variety of painful conditions including posttraumatic auriculotemporal neuralgia, Frey syndrome, Ramsay-Hunt syndrome, temporomandibular joint disorders, and cancer pain. Blockade of the auriculotemporal nerve with botulinum toxin A has also been advocated for the treatment of gustatory sweating syndrome following trauma to the auriculotemporal nerve. Ultrasoundguided blockade of the auriculotemporal nerve provides excellent surgical anesthesia for the repair of lacerations and removal of lesions in the area subserved by the nerve as well as to allow aggressive physical therapy for painful conditions of the temporomandibular joint.

The auriculotemporal nerve is a branch of the third division of the trigeminal nerve, the mandibular nerve (Fig. 5.1). Its fibers leave the mandibular nerve to enter the parotid gland just posterior to the temporomandibular joint. It is at this point that the nerve is often damaged by parotid and temporomandibular joint surgery or compressed by tumors of the parotid gland. The nerve travels cranially passing between the temporomandibular joint and the external auditory meatus, where it gives off branches that provide sensory innervation to the temporomandibular joint and portions of the pinna of the ear and the external auditory meatus. As the nerve ascends across the origin of the zygomatic arch, it joins with the superficial temporal artery as the artery ascends (see Fig. 5.1). The
artery provides an important ultrasonographic landmark when performing auriculotemporal nerve block. As the nerve and artery continue their ascent, the auriculotemporal nerve may pass under the superficial temporal artery, or the artery may intertwine around the nerve (Figs. 5.2 and 5.3). Interestingly, both of the anatomic variations may exist on opposite sides in the same patient. The terminal branches of the auriculotemporal nerve provide sensory innervation to the temporal region and lateral scalp and may interconnect with branches of the facial nerve, and these interconnections may explain why patients suffering from Bell palsy may experience significant associated facial pain (Fig. 5.4).