The Anatomy of the Mandibular Nerve

The mandibular nerve, which plays an important role in moving your mouth, splits off from the trigeminal nerve to connect with the lower jaw. It plays both a motor and sensory role in your head as well as interacting with fibers of other cranial nerves. It's the largest of the three branches of the trigeminal nerve, which is the fifth cranial nerve. The trigeminal nerve is responsible for feeling in your face as well as biting and chewing motions.

Anatomy

Your nerves branch out like trees, with the "limbs" running all throughout your body, carrying sensory information (from your five senses) to and from your brain, and enabling motor function (movement) in your muscles and other moving parts.

You have twelve pairs of cranial nerves in your head. They're symmetrical, with each one having a right and left side. Even so, each pair is referred to as a single nerve.

The rest of the nerves in your body emerge from the spinal cord, but the cranial nerves come from your brain. Most, including the trigeminal nerve, start at the brainstem, which sits at the back of your brain and connects it to the spinal cord.

The mandibular nerve is the largest branch of the trigeminal nerve.

Structure

The trigeminal nerve travels from the brainstem and around your head toward your face. It then splits into three branches: the ophthalmic, maxillary, and mandibular nerves.

The two roots join together to form the trunk, and then the trunk then divides into multiple smaller branches, some motor and some sensory.

This nerve and its branches run past the ear and the temporomandibular joint (jaw), then spread out through the lower part of your face.

Anatomical Variations

The mandibular nerve has been found to have anatomical variations in about 20% of people. These can be found in the mandibular branch itself or in the masseter, temporal, auriculotemporal, or lingual nerves.

Typical variations can be something like the lingual nerve being closer to or farther away from the lower wisdom teeth, or the path of one or more branches being different in relation to other structures. These kinds of abnormalities can lead to nerve damage during surgery or dental procedures because the doctor doesn't expect the nerve to be where it is.

Function

Each branch of the trigeminal nerve provides sensation or motor function to a different area of the head and face.

• Ophthalmic nerve (sensory): Eye, the skin of the upper face, and scalp
• Maxillary nerve (sensory): Upper jaw, the roof of your mouth, nostrils, sinuses, and middle of your face
• Mandibular nerve (sensory and motor): Lower jaw and mouth, some areas of the scalp, and motor function to the lower jaw and mouth

Motor Function

The motor nerves that branch off of the mandibular connect to and move numerous muscles in your face, including:

• Chewing muscles (medial pterygoid, deep temporal, lateral pterygoid, masseter)
• Mylohyoid, which forms the floor of your mouth
• Digastric, which is a small muscle under your jaw
• Tensor veli palatini, which lifts the soft palate at the back of your mouth
• Tensor tympani, inside the ear, which dampens loud noises

Sensory Function

The main sensory nerves that branch off from the mandibular nerve include:

• Meningeal branch, which serves the dura mater (a thick membrane that surrounds the brain and spinal cord)
• Buccal nerve, which transmits sensory information from the cheek and the back two molars
• Auriculotemporal nerve, which provides sensory innervation to the side of your head
• Lingual nerve, which provides sensation to the forward two-thirds of the tongue and the floor of your mouth, and also plays an indirect role in taste
• Inferior alveolar nerve, which runs along the lower teeth and also has some motor function

Associated Conditions

Pain or other problems related to the mandibular nerve can be hard to diagnose due to the complexity of the anatomy in the head and neck. A lot of different structures are close to each other and even overlapping, making it hard for doctors to figure out exactly what's causing symptoms.

The most common condition associated with the mandibular nerve is trigeminal neuralgia. Most cases of this extremely painful condition are due to nerve compression of the mandibular and/or maxillary branches of the trigeminal nerve.

The pain of trigeminal neuralgia is usually only on one side of the face, but in rare cases, both sides are involved. It causes intense pains—described as stabbing or electric-shock-like sensations—to shoot through the jaw and cheek areas. The pain can be triggered by light touch.

This condition is often mistaken for tooth pain due to the nerve's proximity to the teeth. It can also mimic ear pain.

Other problems with the mandibular nerve may arise, as well. Nerve damage, through accidental injury or trauma from surgery or dental procedures, may cause pain, altered sensation, or loss of sensation in the mandibular nerve or any of its many branches.

Rehabilitation

Treatment of problems relating to the mandibular nerve depends largely on the nature of the damage and the symptoms it causes. Treatment may include anti-inflammatories, such as steroids or ibuprofen, and possibly surgical repair.

Several drugs can be used to treat trigeminal neuralgia, including:

• Tegretol (carbamazepine)
• Trileptal (oxcarbazepine)
• Lamictal (lamotrigine)

Several surgical procedures are available for trigeminal neuralgia as well. They're typically only considered when someone doesn't respond well to medications or can't tolerate the drugs due to side effects.