The Anatomy of the Auriculotemporal Nerve

The auriculotemporal nerve is a branch of the mandibular nerve that provides sensation to several regions on the side of your head, including the jaw, ear, and scalp. For much of its course through the structures of your head and face, it runs along the superficial temporal artery and vein.­­­

Anatomy

Your nerves are complex structures. They branch out from their starting points, much like tree limbs. Branches run all throughout your body, connecting to different tissues such as skin, muscles, bones, joints, connective tissues, and even other nerves and clusters of nerves.

Some of your nerves carry information from your five senses—sensory information—to and from your brain. Others enable movement— motor function—in your muscles and other moving parts. Some of them provide both sensory and motor function and are thus called mixed nerves.

In your head, you have 12 symmetrical pairs of cranial nerves. Each one has a right and left side, but they’re typically referred to as a single nerve unless it’s necessary to refer just to the left or right one.

Structure

The fifth cranial nerve is called the trigeminal nerve, which is responsible for biting and chewing motions of your jaw as well as sensation in some areas of your face. The trigeminal nerve splits into three main branches, the:

• Ophthalmic nerve
• Maxillary nerve
• Mandibular nerve

The mandibular nerve is the largest branch of the trigeminal nerve and connects to the lower jaw. Along its course, the mandibular nerve divides into four main branches, which are called the:

• Buccal nerve
• Inferior alveolar nerve
• Lingual nerve
• Auriculotemporal nerve

The auriculotemporal nerve has two roots, a superior root made up of sensory fibers, and an inferior root that carries specialized secretory-motor fibers. It has five main branches, one from the inferior root and four from the superior root:

• Parotid branch (the one from the inferior root)
• Anterior auricular branch
• Articular branch
• Superficial temporal branch
• External auditory meatus branch

Location

The trigeminal nerve travels from the brainstem and around your head toward your face before it gives rise to the mandibular nerve.

The two roots of the auriculotemporal nerve split off near the top of the temporomandibular joint (TMJ), which is in your jaw. The two roots quickly join together. The united nerve then dips down and back toward your ear, where it makes a sharp U-turn and then travels back up toward the top of your head, sending out branches along the way.

Inferior Branch

The inferior branch of the auriculotemporal nerve gives its secretory-motor fibers to the parotid branch. The parotid branch travels first to the otic ganglion (which is a collection of nerve cells in your ear) and there forms a synapse, which is a connection that allows for communication between nerves. The branch then continues on to the parotid gland, from which it takes its name. The parotid gland is one of three types of salivary glands you have. It sits in front of and a little below each of your ear canals, along the cheek and jaw.

Superior Branch

The sensory fibers of the auriculotemporal nerve’s superior branch, meanwhile, pass through the otic ganglion but don’t communicate with it. From there, the nerve sends out its other four main branches. These branches travel to and connect to various structures, providing nerve function (which is called "innervation").

Anatomical Variations

While nerves have typical structures and paths through the body, they’re not exactly the same in everyone. It’s important for doctors and, especially, surgeons to know about the different anatomical variations of nerves so they can properly diagnose and treat nerve-related disorders. It's of special importance to help them avoid damaging nerves during surgery, which may lead to pain, dysfunction, and/or permanent disability, depending on the nerve and the severity of the damage.

The most common known variation of the auriculotemporal nerve is in its number of roots. Having two roots is considered typical, but in studies of cadavers, researchers have found anywhere from one to four roots on each side. Additionally, some people had different numbers on each side, so doctors can't assume the nerve structure is symmetrical.

Other variations included different relationships with the middle meningeal artery, which runs along the auriculotemporal nerve close to where its nerve roots join together.

In the region of the temple, on the side of the forehead, branches of the nerve run close to the surface and therefore are vulnerable to being injured. Research shows considerable variation in the branches through that region, with some people having as few as two branches per side and others having as many as seven per side. Their distances from certain structures varied as well, and in some people, the communicating branches of the nerve formed a loop. In one case, it formed two loops.

Other research shows that the parotid branch varies in how far it lies from major structures. In addition, some people have also been found to have two parotid branches instead of the usual single branch per side.

Function

Because the auriculotemporal nerve serves both sensory and specialized motor function, it’s classified as a mixed nerve.

Secretory-Motor Function

The single motor function of the auriculotemporal nerve’s inferior branch deals with the parotid gland. The nerve allows the gland to secrete saliva, which is where the term secretory-motor comes from.

The parotid gland is one of three salivary glands that keep your mouth moist, which helps you chew food and starts the process of digestion. Saliva also helps prevent cavities by defending your mouth against bacteria.

When the parotid gland secretes saliva via the action of the auriculotemporal nerve, the liquid is carried to your mouth by ducts.

Sensory Function

The superior portion of the auriculotemporal lobe, and the four branches it sends out, allow for the skin and other structures in the areas they innervate to recognize sensation (touch, temperature, etc.) and transmit it to the brain.

• Anterior auricular branch: Innervates the forward external surface of the ear (auricle).
• Superficial temporal branch: Innervates the skin over your temple.
• Articular branch: Innervates the rear portion of the temporomandibular joint.
• External auditory meatus branch: Innervates the forward external portion of the outer ear (external meatus) and the eardrum (tympanic membrane).

Associated Conditions and Treatments

As with any nerve, the auriculotemporal nerve can be impaired by traumatic damage (injury to the area it runs through) or diseases that impact nerves (i.e., multiple sclerosis, cerebral palsy).

The most common problems that are directly related to this nerve are entrapment or compression, neuralgia, Frey syndrome, and injury during TMJ surgery.

Entrapment/Compression

The auriculotemporal nerve can be affected by damage to or compression of it or its branches, or of the mandibular nerve before it branches off. The mandibular nerve can be compressed by several known anatomical irregularities along its route.

The diagnosis of entrapment is made by physical examination and the injection of a local anesthetic over the nerve. Treatment may include pain medications, nerve injections, removal of problem tissues through various methods, including surgery, to relieve the pressure.

Neuralgia

Neuralgia (pain from nerve damage) of the auriculotemporal nerve can cause throbbing pain at any of the sites where it connects to structures, including:

• Temporomandibular joint
• Skin of the external ear structure or outer ear
• Skin of the scalp
• Parotid gland

This type of neuralgia is somewhat rare and the diagnosis is difficult because many other problems can cause the same symptoms, including TMJ disease, migraine, and ear infection. Typically, diagnosis is made by using a nerve block to see whether it resolves symptoms. Once the diagnosis is made, it can be treated. The standard treatment is the injection of botulinum toxin.

Frey Syndrome

Surgical removal of the parotid gland can result in a complication called Frey syndrome. After the gland is gone from the cheek, the auriculotemporal nerve’s parotid branch sometimes attaches itself to the sweat glands in the same area.

That leads to sweating along the cheek while you eat, which is when the parotid branch would normally be causing the parotid gland to release saliva.

Conservative treatment can involve antiperspirant on the cheek. There’s also a surgical option, which involves placing a different tissue in between the nerve and the sweat gland so the nerve can no longer cause the gland to activate.

Injury During TMJ Surgery

Because of its relationship to the temporomandibular joint and the parotid gland, the auriculotemporal nerve is vulnerable to injury during TMJ surgery. The result of this injury can be abnormal nerve sensations such as tingling, burning, itching, or electrical “zings,” which are called paresthesias.

Nerve Block as TMJ Pain Relief

Of note is that the auriculotemporal nerve is sometimes involved in treating TMJ. Nerve blocks have been shown effective at reducing pain caused by dysfunction of the joint. This is usually reserved for patients who don’t find relief with conservative treatments.