Anatomy, Head and Neck: Auriculotemporal Nerve

Structure and Function

The auriculotemporal nerve contains secretomotor, somatosensory, and vasomotor fibers. Sensory fibers of this peripheral branch of the mandibular nerve have 1st-order neuron cell bodies located in the trigeminal ganglion. After the mandibular nerve exits the skull through the foramen ovale, the auriculotemporal nerve usually arises from the posterior division by 2 roots, commonly described as "superior" and "inferior," which encircle the middle meningeal artery before uniting to form a single trunk. After fusion of both roots at approximately 1 to 2 cm posterior to the mandibular nerve, the auriculotemporal nerve courses posterior to the lateral pterygoid muscle and passes between the sphenomandibular ligament and the neck of the mandible.

The auriculotemporal nerve ascends through the parotid region in close relation to the neck of the mandible and the TMJ. Close association with the superficial temporal vessels is maintained as the nerve continues superiorly into the temporal region. Communication with branches of the facial nerve (cranial nerve VII) may occur along the course of the auriculotemporal nerve.

The superior root of the auriculotemporal nerve contains general somatic afferent fibers that provide sensation to portions of the auricle, the EAM, the TMJ, and the temporal scalp. Sensory fibers have cell bodies located in the trigeminal ganglion and project centrally to the trigeminal sensory nuclei in the brainstem.

The inferior root carries postganglionic parasympathetic secretomotor fibers from the otic ganglion to the parotid gland. Preganglionic parasympathetic fibers originate from the inferior salivatory nucleus in the brainstem, travel with the glossopharyngeal nerve (cranial nerve IX) via the tympanic branch to the tympanic plexus, continue as the lesser petrosal nerve, and synapse in the otic ganglion. Postganglionic fibers then accompany the auriculotemporal nerve en route to the parotid gland.

Embryology

The auriculotemporal nerve is a branch of the mandibular division of the trigeminal nerve and is associated with the 1st pharyngeal arch. The auriculotemporal nerve also carries postganglionic parasympathetic fibers to the parotid gland. These fibers arise from the glossopharyngeal nerve, associated with the 3rd pharyngeal arch, synapse in the otic ganglion, and then join the auriculotemporal nerve (see Image. Mandibular Development in a Human Embryo).

Nerves

The 5 main branches of the auriculotemporal nerve are the anterior auricular, articular, parotid, superficial temporal, and EAM branches. The anterior auricular branch provides somatosensory innervation to the skin of the ear, including the tragus and part of the helix. The articular branch provides somatosensory innervation to the posterior aspect of the TMJ.

The parotid branch carries postganglionic fibers arising from the glossopharyngeal nerve via the tympanic plexus and lesser petrosal nerve after synapsing in the otic ganglion. This branch provides secretomotor parasympathetic innervation and vasomotor sympathetic innervation to the parotid gland. The superficial temporal branches course posterior to the superficial temporal artery and provide somatosensory innervation to the skin over the temporal region. Communication with the facial nerve and the zygomaticotemporal nerve, a branch of the maxillary division of the trigeminal nerve (cranial nerve V2), may occur (see Image. Maxillary and Mandibular Nerve Distribution). The branch to the EAM provides somatosensory innervation to the skin of the meatus and part of the tympanic membrane.

Physiologic Variants

The most common variant of the auriculotemporal nerve is observed in its root pattern arising from the mandibular nerve. Although the auriculotemporal nerve most often has 2 roots, the literature describes variations in both the number and location of these roots. Two reports of cadaveric dissections described multiple branching patterns, with findings demonstrating as few as 1 and as many as 4 roots arising from the mandibular nerve.[1][2]

Surgical Considerations

Surgical consideration is required in multiple procedures due to the complex course of the auriculotemporal nerve (see Image. Superficial Neurovascular Structures of the Temporal Region). During TMJ surgery, the auriculotemporal nerve is vulnerable to injury as it courses 10 to 13 mm inferior to the superior edge of the mandibular condyle.[3][4] Injury during surgical intervention may result in pain or paresthesia affecting all terminal branches distal to the lesion (see Nerves). Parotidectomy is another procedure in which preservation of the auriculotemporal nerve is essential. Following this procedure, parasympathetic secretomotor fibers previously innervating the parotid gland may be damaged and undergo aberrant regeneration to sweat glands and cutaneous blood vessels in the overlying skin, resulting in Frey syndrome (see Clinical Significance).[5]

Clinical Significance

Various conditions can affect auriculotemporal nerve function.[6] Selected disorders are discussed below.

Neuralgia of the auriculotemporal nerve presents as throbbing unilateral pain in any of its terminal distribution areas, including the TMJ, scalp, EAM, auricle, and parotid region. Neuralgia may arise from compression of the nerve, particularly by the lateral pterygoid muscle during mastication. The condition is uncommon, with an incidence of approximately 0.4%. Diagnosis may be challenging due to nonspecific symptomatology and a broad differential diagnosis, including cervicalgia, TMJ disease, migraine, hemicrania continua, otitis, trigeminal neuralgia, atypical facial pain, temporal arteritis, and odontalgia. Diagnostic confirmation may be achieved by nerve blockade with complete resolution of symptoms.[7][8] Botulinum toxin injection may provide symptomatic relief.[9]

The auriculotemporal nerve is vulnerable during surgical procedures due to its close anatomic relationships with the parotid gland, TMJ, EAM, and middle meningeal artery. Injury may result in temporal pain, neuralgia, paresthesia, and reduced secretomotor function to the parotid gland.

Frey syndrome, also referred to as "auriculotemporal syndrome," "Baillarger syndrome," "Dupuy syndrome," or "gustatory hyperhidrosis," is named after Jules Baillarger, who first described the manifestations, and Lucia Frey, who systematized the condition. Frey syndrome presents as unilateral sweating of the cheek and external ear, accompanied by erythema following eating or drinking. Gustatory stimulation is not always required for symptom onset. Frey syndrome may also occur in response to olfactory or cognitive stimuli, including thinking about, seeing, or dreaming about food that induces salivation.

Frey syndrome results from injury to the auriculotemporal nerve, in which damaged parasympathetic fibers undergo aberrant regeneration to innervate sweat glands and cutaneous blood vessels in the overlying skin. Frey syndrome most commonly occurs secondary to parotid surgery, parotid gland infection, or facial trauma, and is the most frequent adverse effect following parotidectomy.[10][11]

Differentiation from primary or secondary hyperhidrosis, emotional sweating, pediatric food allergy, and Bogorad syndrome (crocodile tears syndrome) is required. Diagnosis relies primarily on clinical presentation and a history of prior trauma or surgery involving the parotid or auriculotemporal region. The Minor starch–iodine test may be performed when diagnostic confirmation is required. This test involves the application of iodine followed by starch to the skin, with sweating producing a characteristic blue discoloration. Treatment options include botulinum toxin injection and topical aluminum chloride. Intraoperative flaps and implants may reduce the risk of aberrant reinnervation and subsequent symptom development.

Perineural tumor spread along the auriculotemporal nerve may extend cranially through the foramen ovale to the skull base. Extension to the skull base may produce trigeminal pain or palsy and involve adjacent infratemporal and vascular structures.

First bite syndrome is an important postoperative complication of deep parotid lobe surgery. The condition is characterized by severe cramping pain in the parotid region during the first bite of each meal, with symptoms typically diminishing as the meal progresses. First bite syndrome is thought to result primarily from damage to postganglionic sympathetic fibers, leading to relative parasympathetic overactivity and exaggerated myoepithelial contraction, rather than isolated auriculotemporal nerve injury.

Auriculotemporal nerve involvement in parotid malignancy is relatively uncommon but is likely underrecognized. Reported manifestations include periauricular pain, facial weakness, and local tumor recurrence.