Introduction to Trigeminal Neuralgia

Trigeminal neuralgia (TN), also known as tic douloureux, is the most common facial pain syndrome. It is often described as "the most terrible pain known to man".

There are 12 pairs of nerves, called cranial nerves, which provide the nerve supply to (innervate) the right and left side of the head and neck. The 12 pairs of cranial nerves, designated by Roman numerals I through XII, include:

• I = Olfactory Nerve - innervates the nose and enables us to smell odors
• II = Optic Nerve - innervates the eye enables us to visualize objects
• III = Oculomotor Nerve - innervates the muscles of the eye and enables us to move our eyelids and eyeballs
• IV = Trochlear Nerve - innervates the superior oblique eye muscle and controls ability to move our eyes downward and from side to side
• V = Trigeminal Nerve - enables us to chew and feel sensations of the mouth and face (e.g., touch and pain)
• VI = Abducens Nerve - innervates the lateral rectus eye muscle which moves the eye laterally
• VII = Facial Nerve - innervates the face and controls our facial expressions, ability to produce and secrete saliva and tears, and ability to taste foods and beverages
• VIII = Vestibulocochlear (auditory) Nerve - innervates the ears and controls our ability to hear and maintain equilibrium (balance)
• IX = Glossopharyngeal Nerve - innervates the tongue and the pharynx (back of the throat) and is involved in taste sensation
• X = Vagus Nerve - involved in controlling blood pressure, heart rate, stimulation of digestive organs, and taste
• XI = Spinal Accessory Nerve - innervates the trapezius muscle and controls our ability to swallow
• XII = Hypoglossal Nerve - innervates the muscles of the tongue and controls our ability to move the tongue

The trigeminal nerve is the 5th and largest of the cranial nerves and is designated as cranial nerve number V. It provides nerve sensation to the face, mouth, and the front of the scalp as well as controlling the muscles involved in chewing (mastication).

The trigeminal nerve has three branches.

• The ophthalmic branch runs through the eye, forehead and nose.
• The maxillary branch runs through the upper teeth, gums, lips, cheek, lower eyelid and side of the nose.
• The mandibular branch runs through the lower teeth, gums and lip. It also controls jaw movement for mastication or chewing.

The three branches of the trigeminal nerve come together in an area called the Gasserian ganglion. From there, the trigeminal nerve root continues along the side of the brain stem and inserts into a portion of the brainstem called the pons.

Trigeminal neuralgia most often affects the mandibular branch or the maxillary branch. One study found the division of pain to be:

• 44% in the maxillary branch
• 35% in the mandibular branch
• 19% in the ophthalmic branch

Most patients complain of pain in both the maxillary and mandibular branches.

Trigeminal neuralgia is considered by the National Organization of Rare Diseases (NORD) to be a rare condition that affects approximately 1.7 million people in the US, though estimates vary widely. It is estimated in some studies that approximately 4 in 100,00 people develop TN each year in the United States. The average age of onset is between 50 and 70 years old, though it can be seen in younger people as well.