Introduction to trigeminal neuralgia (TN)
The brain is connected to the body by the spinal cord with spinal nerves sending and receiving impulses and messages to and from the brain. However, there are twelve cranial nerves that directly connect to the body. These nerves are involved with the muscle and sensory function of the head and neck. (The exception is cranial nerve X or the vagus nerve, which is also responsible for the parasympathetic system of the chest and abdomen).
|III, IV, VI||Oculomoter, Trochlear, Abducens||Eye movement|
|V||Trigeminal||Facial sensation, chewing|
|X||Vagus||Swallowing, voice modulation, parasympathetic tone of the body|
|XII||Hypoglossal||Swallowing, speech articulation|
- The ophthalmic branch (V1) is responsible for sensation from the scalp, forehead, upper eyelid and tip of the nose.
- The maxillary branch (V2) sensation covers the lower eyelid, the side of the nose, the upper lip and cheek, and the upper teeth and gums.
- The mandibular branch (V3) is responsible for sensation of the lower teeth and gums, lower lip, chin, jaw, and part of the ear. It is also responsible for supplying the muscles involved with chewing (mastication), those muscles involved with chewing.
What is trigeminal neuralgia (TN)?
Trigeminal neuralgia is inflammation of the trigeminal nerve, causing intense facial pain. It is also known as tic douloureax because the intense pain can cause patients to contort their face into a grimace and cause the head to move away from the pain. The obvious movement is known as a tic.
The pain of trigeminal neuralgia is intense and may be an isolated episode or may be occur every few hours, minutes, or seconds. There can be months or years between attacks, but in some patients whose pain is not well controlled; it can lead to a chronic pain syndrome, affecting activities of daily life and cause depression.
Though it can affect people of any age, trigeminal neuralgia tends to afflict people older than 60 years of age. It affects the right side of the face five times more often than the left.
What causes trigeminal neuralgia?
Most often, the cause of trigeminal neuralgia is idiopathic, meaning the cause is not known. There are some instances when the nerve can be compressed by nearby blood vessels, aneurysms, or tumors.
There are inflammatory causes of trigeminal neuralgia because of systemic diseases including multiple sclerosis, sarcoidosis, and Lyme disease. There also is an association with collagen vascular diseases including scleroderma and systemic lupus erythematosus.
What are the symptoms of trigeminal neuralgia?
Symptoms of trigeminal neuralgia include an acute onset of sharp, stabbing pain to one side of the face. It tends to begin at the angle of the jaw and radiate along the junction lines; between the ophthalmic branchV1 and maxillary branch V2, or the maxillary branch V2 and the mandibular branch V3.
The pain is severe and described as an electric shock. It may be made worse by light touch, chewing, or cold exposure in the mouth. In the midst of an attack, affected individuals shield their face trying to protect it from being touched. This is an important diagnostic sign because with many other pain syndromes like a toothache, the person will rub or hold the face to ease the pain.
While there may be only one attack of pain, the person may experience recurrent sharp pain every few hours or every few seconds. Between the attacks, the pain resolves completely and the the person has no symptoms. However, because of fear that the intense pain might return, people can be quite distraught. Trigeminal neuralgia tends not to occur when the person is asleep, and this differentiates it from migraines, which often waken the person.
After the first episode of attacks, the pain may subside for months or years but there is always the risk that trigeminal neuralgia will recur without warning.
How is trigeminal neuralgia diagnosed?
Idiopathic trigeminal neuralgia is a clinical diagnosis and often no testing is required after the health care professional takes a history of the situation and performs a physical examination which should be normal.
It is important to remember that the neurologic exam must be normal. There are two specific areas to test. There can be no muscle weakness; V3 is responsible for chewing and there can be no jaw or facial weakness found. The corneal reflex controlled by V1 must be present. When the cornea or covering of the eye is touched, the eye blinks in response. If these two findings are not normal, the search should begin for an inflammatory or compression cause of the trigeminal nerve. Some clinicians may order an MRI to help diagnose other conditions that may cause trigeminal neuralgia.
The International Headache Society has established criteria for making the diagnosis and includes the following:
- Paroxysmal attacks of pain lasting from a fraction of a second to 2 minutes, affecting 1 or more divisions of the trigeminal nerve and fulfilling criteria B and C.
- Pain has at least one of the following characteristics: (1) intense, sharp, superficial or stabbing; or (2) precipitated from trigger areas or by trigger factors
- Attacks stereotyped in the individual patient
- No clinically evident neurologic deficit
- Not attributed to another disorder
What is the treatment for trigeminal neuralgia?
- Idiopathic trigeminal neuralgia most often is treated with good success using a single anticonvulsant medication such as carbamazepine (Tegretol).
- Gabapentin (Neurontin, Gabarone), baclofen and phenytoin (Dilantin, Dilantin-125) may be used as second line drugs, often in addition to carbamazepine. In many patients, as time progresses, carbamazepine becomes less effective and these drugs can be used in combination to control the pain.
- Should pain persist and medication fail to be effective, surgery or radiation therapy may be other treatment options.
- Lamotrigine (Lamictal) may be prescribed for multiple sclerosis patients who develop trigeminal neuralgia.
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The International Classification of Headache Disorders: 2nd edition. Cephalalgia. 2004; 24 Suppl 1:9-160.