Auriculotemporal nerve

Overview
The auriculotemporal nerve is a branch of the mandibular nerve that runs with the superficial temporal artery and vein, and provides sensory innervation to various regions on the side of the head.

Origin
The auriculotemporal nerve arises as two roots from the posterior division of the mandibular nerve. These roots encircle the middle meningeal artery (a branch of the mandibular part of the maxillary artery, which is in turn a terminal branch of the external carotid artery). The roots then converge to form a single nerve.

Course
The auriculotemporal nerve passes medially to the neck of the mandible, gives off parotid branches and then turns superiorly, posterior to its head and moving anteriorly, gives off anterior branches to the auricle. It then crosses over the root of the zygomatic process of the temporal bone, deep to the superficial temporal artery

Innervation
The somatosensory root (superior) originates from branches of the mandibular nerve, which pass through the otic ganglion without synapsing. Then they form the somatosensory (superior) root of the auriculotemporal nerve. The two roots re-unite and shortly after the branching of secretomotor fibers to the parotid gland (parotid branches) the auriculotemporal nerve comprises exclusively somatosensory fibers, which ascend up to the superficial temporal region. Supplies the auricle, external acoustic meatus, outer side of the tympanic membrane and the skin in the temporal region (superficial temporal branches).

The parasympathetic root (inferior) carries postganglionic fibers to the parotid gland. These parasympathetic, preganglionic secretomotor fibers originate from the glossopharyngeal nerve (CN IX) as one of its branches, the lesser petrosal nerve. This nerve synapses in the otic ganglion and its postganglionic fibers from the inferior, parasympathetic root of the auriculotemporal nerve. The two roots re-unite and shortly after the "united" auriculotemporal branch gives off parotid branches, which serve as secretomotor fibers for the parotid gland.

Clinical significance
This nerve as it courses posteriorly to the condylar head, is frequently injured in temporomandibular joint surgery, causing an ipsilateral parasthesia of the auricle and skin surrounding the ear.