The auriculotemporal nerve is a tributary of the mandibular division of cranial nerve five, the trigeminal nerve. It contains sensory, vasomotor, and parasympathetic fibers. It has a superior and inferior root that originates from the trigeminal nerve, encircles the middle meningeal artery ultimately traveling inferior to the temporomandibular joint and up the temple providing sensation to parts of the ear, temporomandibular joint, scalp, as well as secretory and vasomotor innervation to the parotid gland. This nerve is clinically relevant in the setting of temporal mandibular joint disease repair, postoperative complications in a parotidectomy, and trigeminal neuralgia.
The auriculotemporal nerve contains secretomotor, somatosensory, and vasomotor fibers. This nerve originates from the sensory nucleus of the trigeminal nerve in the pons. The mandibular branch of the trigeminal nerve exits the cranium out of the foramen ovale. After exiting the skull, the auriculotemporal nerve branches off where it has a superior and posterior root encircling the middle meningeal artery before joining together to form one nerve. After both roots fuse, it continues posterior to the lateral pterygoid muscle and travels between the sphenomandibular ligament and the neck of the mandible. The nerve lies posterior the parotid gland where it gives off parasympathetic and vasomotor fibers before it travels just inferior to the superior aspect of the mandibular condyle of the temporal mandibular joint. As it continues to travel superior, past the temporal mandibular joint, in the infratemporal fossa, it shares an intimate relationship with the superficial temporal artery. Along its path, it anastomoses with the facial nerve on the and the otic ganglion.
The superior root of the auriculotemporal nerve contains general somatic afferent fibers that provide sensation to the tragus and helix of the ear, the external portion of the tympanic membrane, the posterior temporomandibular joint, and the temple. The fibers originate from the trigeminal nucleus in the pons and travel with the mandibular division of the trigeminal nerve through the foramen ovale.
The inferior root of the auriculotemporal nerve contains general visceral efferent fibers that provide autonomic parasympathetic innervation to the parotid gland. The fibers originate in the inferior salivary nucleus as part of cranial nerve nine, the glossopharyngeal nerve, it passes through the tympanic canaliculus and divides into its branches, including, the lesser petrosal nerve. The lesser petrosal nerve synapses in the otic ganglion and the postsynaptic fibers pass to the auriculotemporal nerve.
The auriculotemporal nerve is a division of the trigeminal nerve with some post otic ganglionic parasympathetic fibers from the glossopharyngeal nerve. The embryologic derivative of the trigeminal nerve is the first pharyngeal arch that begins to form around the fourth week of gestation and ultimately provides sensation to the ophthalmic, maxillary, and mandibular regions of the face, as well as motor function to the muscles of mastication in the developing fetus. The embryologic derivative of cranial nerve nine, the glossopharyngeal nerve, is the third pharyngeal arch which begins developing in the fourth week of gestation and provides branchial motor innervation to the stylopharyngeus muscle, general visceral efferent via parasympathetic fibers, and visceral sensory from the carotid body and sinus.
There are five main branches to the auriculotemporal nerve; the anterior auricular, articular, parotid, superficial temporal and branches to the external auditory meatus:
The most common variant of the auriculotemporal nerve is seen in its branching pattern off of the trigeminal nerve. Although most often, the nerve has two roots, and an inferior root and a superior root, the literature describes variations of the number and location of the roots. In two reports of cadaveric dissections, there were various branching patterns reported, and researchers found that as few as one and as many as four roots can arise from the trigeminal nerve.
Due to the complex path of the auriculotemporal nerve, it merits consideration in various surgical procedures. In temporomandibular joint surgery, the nerve is vulnerable to damage as it courses 10 to 13 mm inferior to the superior edge of the mandibular condyle. If damaged during surgery, the patient can develop pain or paresthesias in all terminal branches distal to the lesion, noted in the ‘Nerves' section above. Another surgical procedure in which preservation of this nerve is essential is in parotidectomy. Post parotidectomy, parasympathetic secretomotor fibers which were innervating the parotid gland can be damaged and have inappropriate regeneration to sympathetic receptors on salivary glands, which results in Frey syndrome discussed in Clinical Significance section below.
Auriculotemporal nerve neuralgia and Frey syndrome are two common disorders of the auriculotemporal nerve.
Frey syndrome is unilateral sweating of the cheek and external ear accompanied by reddening of the area seen after eating or drinking food. Interestingly, it can also present if the affected patient thinks, sees, or dreams about food that causes salivation. The syndrome results from a lesion of the auriculotemporal nerve where inappropriate regeneration of damaged parasympathetic fibers regenerates innervating sympathetic receptors of salivary glands in the face. Frey syndrome is most commonly seen secondary to surgery, parotid gland infection or facial trauma and is the most common adverse side effect of a parotidectomy. Treatment of Frey syndrome can include botulinum toxin, aluminum chloride, epoetin or intraoperative flaps, and implants can be used to prevent the seeding of fibers into unwanted locations.
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