Anatomy, Head and Neck, Auriculotemporal Nerve

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: 

1. The anterior auricular branch provides somatosensory innervation to the skin of the ear, including the tragus and part of the helix.
2. The articular branch provides somatosensory innervation to the posterior temporal mandibular joint
3. The parotid branch receives its preganglionic fibers from the lesser petrosal nerve of the tympanic plexus originating from the glossopharyngeal nerve, before sending postganglionic general visceral efferent fibers within the parotid branch of the auriculotemporal nerve. This branch provides secretomotor innervation via parasympathetic fibers to the parotid gland and vasomotor via sympathetic innervation. 
4. The superficial temporal branches run posterior to the superficial temporal artery. These branches provide somatosensory innervation to the skin over the temple. This branch also anastomoses with the facial nerve and zygomaticotemporal nerve, a branch of the maxillary division of cranial nerve five, the trigeminal nerve.
5. The branch to the external auditory meatus provides somatosensory innervation to the skin of the meatus as well as the tympanic membrane.