The auriculotemporal nerve is a sensory branch of the mandibular division (V3) of the trigeminal nerve (cranial nerve V). It carries sensory fibers from the skin of the temporal region, external ear, and parts of the scalp. The nerve also conveys parasympathetic fibers from the otic ganglion to the parotid gland for salivation, though it primarily functions in sensory roles.
Location
The auriculotemporal nerve originates in the infratemporal fossa from the mandibular nerve. It then travels posteriorly, looping around the middle meningeal artery. Afterward, it courses superiorly along the side of the face, emerging near the temporomandibular joint (TMJ), running anterior to the ear and extending upward toward the temporal region and scalp. It lies in close proximity to the superficial temporal artery as it ascends.
Structure and Anatomy
Origin
The auriculotemporal nerve originates from the posterior division of the mandibular nerve, which is the third division (V3) of the trigeminal nerve (cranial nerve V). This nerve arises within the infratemporal fossa and is one of the primary sensory branches of the mandibular division.
Formation and Early Course
The auriculotemporal nerve is formed by two roots that encircle the middle meningeal artery as it branches from the mandibular nerve. These two roots are a distinctive feature, as they split and then reunite around the artery, creating a loop. This occurs within the infratemporal fossa, where the nerve remains closely related to the nearby structures.
Infratemporal Fossa and Relationship with Surrounding Structures
Within the infratemporal fossa, the auriculotemporal nerve travels posteriorly and laterally. Its position relative to the middle meningeal artery, as well as its close association with the pterygoid muscles and mandibular nerve branches, defines its anatomical relationships in this region. Additionally, the nerve runs near the external carotid artery as it ascends.
Parotid Gland and Temporal Course
The auriculotemporal nerve continues to travel posteriorly and emerges between the temporomandibular joint (TMJ) and the external acoustic meatus, lying adjacent to the parotid gland. After passing through or near the gland, the nerve ascends alongside the superficial temporal artery, paralleling its course toward the scalp.
Path Alongside the Superficial Temporal Artery
As the nerve exits the infratemporal fossa and courses toward the temporal region, it runs with the superficial temporal artery, a branch of the external carotid artery. The auriculotemporal nerve ascends anterior to the ear, along the posterior aspect of the mandible, continuing superiorly toward the scalp.
Innervation of External Ear and Temporal Region
The nerve supplies several branches as it travels. It provides innervation to the external ear, specifically the anterior auricle, external acoustic meatus, and parts of the tympanic membrane. It also distributes sensory fibers to the skin over the temporal region, where it supplies the scalp and anterior ear.
Communication with Other Nerves
The auriculotemporal nerve forms connections with other nerves, such as the facial nerve branches near the ear. It may also communicate with branches of the greater auricular nerve, providing sensory redundancy for the innervated regions.
Terminal Branches
The terminal branches of the auriculotemporal nerve extend into the scalp and temporal region. These branches supply the skin over the lateral scalp and the temple area. This final course allows the nerve to innervate not only the superficial areas of the scalp but also small parts of the external ear and adjacent tissues.
Parasympathetic Fibers from the Otic Ganglion
Although the auriculotemporal nerve is primarily sensory, it carries parasympathetic fibers from the otic ganglion, which are responsible for innervating the parotid gland. These fibers travel alongside the auriculotemporal nerve after originating in the otic ganglion. However, these parasympathetic fibers are not inherent to the auriculotemporal nerve itself, but they accompany it along its course.
Function
The auriculotemporal nerve has several important sensory and autonomic functions. While it is primarily a sensory nerve, it also carries parasympathetic fibers to the parotid gland. Below is a detailed explanation of its functions:
Sensory Innervation to the Temporal Region
The auriculotemporal nerve provides general sensory innervation to the skin of the temporal region. This includes the lateral aspect of the scalp, the skin above the ear, and the anterior portion of the temple. The sensory fibers relay information such as:
- Touch and Pressure: The nerve transmits tactile stimuli from the skin, allowing the sensation of touch and pressure in the temporal region.
- Pain and Temperature: The nerve carries sensory information about pain and temperature, which is important for detecting injuries or temperature changes on the surface of the skin in this area.
Sensory Innervation to the External Ear
The auriculotemporal nerve also supplies sensory innervation to parts of the external ear, including:
- Anterior Auricle: It innervates the skin on the anterior aspect of the auricle (the outer ear).
- External Acoustic Meatus: The nerve supplies sensation to the skin lining the external acoustic meatus (the ear canal), which is important for detecting foreign bodies, infections, or injuries.
- Tympanic Membrane: The auriculotemporal nerve partially innervates the outer surface of the tympanic membrane (eardrum), allowing sensory perception of pain and pressure changes.
Sensory Innervation to the Temporomandibular Joint (TMJ)
The auriculotemporal nerve plays a key role in the sensory innervation of the temporomandibular joint (TMJ). It transmits sensory information regarding:
- Joint Movement and Pressure: The nerve relays tactile and proprioceptive feedback from the TMJ, providing information about joint movement and pressure changes during chewing or jaw movement.
- Pain Perception in TMJ Disorders: Sensory fibers from the nerve detect pain associated with conditions affecting the TMJ, such as temporomandibular disorders (TMD) or arthritis. This pain can radiate to the temporal or ear region.
Sensory Innervation to the Parotid Gland
The auriculotemporal nerve provides sensory innervation to the parotid gland, which is the largest salivary gland located near the jaw and in front of the ear. Although its parasympathetic fibers are crucial for salivary secretion, the auriculotemporal nerve itself supplies the gland with sensory fibers that help relay information such as:
Pain and Discomfort: Sensory fibers detect inflammation or swelling in the parotid gland, particularly in conditions such as infections (parotitis) or parotid gland tumors.
Parasympathetic Secretomotor Innervation to the Parotid Gland
Although the auriculotemporal nerve is primarily sensory, it also carries parasympathetic secretomotor fibers originating from the otic ganglion, which innervates the parotid gland. These fibers are responsible for:
Stimulating Salivary Secretion: The parasympathetic fibers carried by the auriculotemporal nerve are involved in stimulating the production and release of saliva from the parotid gland. These fibers originate from the glossopharyngeal nerve (cranial nerve IX) and reach the parotid gland by traveling with the auriculotemporal nerve.
Communication with Other Nerves
The auriculotemporal nerve forms communications with various nearby nerves, allowing sensory information to be transmitted more broadly in the surrounding regions. These connections include:
- Facial Nerve (Cranial Nerve VII): The auriculotemporal nerve communicates with branches of the facial nerve near the ear and scalp. This allows for an overlap in sensory innervation between regions supplied by the trigeminal and facial nerves.
- Greater Auricular Nerve: The auriculotemporal nerve may also connect with branches of the greater auricular nerve, a branch of the cervical plexus that supplies parts of the ear and parotid region. This connection provides redundancy in sensory innervation to the skin of the ear and surrounding area.
Clinical Significance
The auriculotemporal nerve is clinically significant due to its involvement in sensory and parasympathetic functions, particularly in the head and neck region. Damage or irritation to this nerve can result in auriculotemporal neuralgia, characterized by sharp, localized pain in the temple and around the ear. The nerve’s close relationship with the temporomandibular joint (TMJ) means it plays a role in pain perception related to TMJ disorders, which can cause discomfort in the jaw, ear, and temporal region.
Additionally, the auriculotemporal nerve is implicated in Frey’s syndrome (gustatory sweating), where parasympathetic fibers misdirect to sweat glands after surgery or injury to the parotid gland. This condition results in sweating and flushing of the skin over the parotid region when eating. The nerve’s proximity to the parotid gland makes it vulnerable during surgeries like parotidectomy, increasing the risk of such complications.
