Trigeminal neuralgia overview

# Overview
Trigeminal neuralgia (TN) is a neuropathic disorder of the trigeminal nerve that causes episodes of intense pain in the eyes, lips, nose, scalp, forehead, and jaw.It is also known as Tic Douloureux or Fothergill's disease (named after John Fothergill). Trigeminal nerve is one of the largest and widely distributed cranial nerve with three branches ophthalmic nerve (V1), maxillary nerve (V2) and mandibular nerve (V3). Ophthalmic and maxillary are purely sensory, while mandibular nerve has both sensory and motor functions. Pain of trigeminal neuralgia affects sensory distributions and typically radiates to maxillary and mandibular divisions in 35% of affected individuals. International Association of Study of Pain (IASP) defined TN as "sudden usually unilateral severe brief stabbing recurrent pain in the distribution of one or more branches of 5th cranial nerve". Similarly, International Headache society (IHS) defined it as "painful unilateral affliction of face characterized by brief electric shock like pain limited to the distribution of one or more divisions of trigeminal nerve". TN is usually characterized by paroxysmic episodes of sudden, severe, shock like pain that lasts for seconds to a few minutes. It is almost always unilateral, but is bilateral in rare cases, and right side is affected more often than the left side. These episodes can occur spontaneously or can be triggered by a mild cutaneous stimuli like chewing, shaving, touching, brushing teeth or even air currents can trigger an episode. The pain tends to occur in cycles with remissions lasting months or even years. These episodic attacks are known to worsen in frequency or severity overtime and can have a significant impact on a person's quality of life, resulting in problems such as weightloss, depression and, in severe cases, suicide. Attacks may provoke patients to grimace, wince or make an aversive head movement, known as tic, hence the term 'tic douloureux". Data is not consistent, but some studies have shown that migraine and hypertension can act as a risk factor for trigeminal neuralgia. According to etiology, IHS has classified TN into three main categories classical, secondary and idiopathic TN. Although majority of the cases of TN are idiopathic but other causes may include systemic diseases like multiple sclerosis, diabetes mellitus, infectious conditions caused by Mycobacterium leprae, Secondary syphilis, Leptospirosis etc, injuries to trigeminal nerve both centrally and peripherally caused by trauma, ENT pathologies, intracranial tumors, cysts, arteriovenous malformations, tuberculomas and allergic reactions. Pathology of TN is related to demyelination and dystrophy of nerve caused by above mentioned etiological factors. Allergic reaction and its frequent manifestations such as cold, chronic rhinitis, maxillary sinusitis, tonsillitis and chronic inflammation can trigger immune response which in turn results in accumulation of immunoglobulins and histamine in trigeminal nerve region and play role in TN pathogenesis. Diagnosis of TN is mainly clinical, based primarily on history, physical examination and neurological examination, but other causes of facial pain should be ruled out. Common differentials include glossopharyngeal neuralgia, cracked tooth syndrome, cluster headaches and postherpetic neuralgia. Treatment of TN depends upon severity and underlying cause of disease and include medicines mainly anti epileptics, surgery and complimentary approaches. Carbamazepine is the first line drug used for initial management. However, as it is a long term condition, some people overtime may stop responding to medications, or they may experience unpleasant side effects. For those people surgical options can be considered. Psychosocial support also plays an important role in improving quality of life.

# Historical Perspective
Trigeminal neuralgia is considered by many to be among the most painful of conditions and once was labeled the suicide disease because of the significant numbers of people taking their own lives before effective treatments were discovered. In 1773, John Fothergill presented his detailed description of TN " a painful affection of the face" to the Medical Society to London, hence the name Fothergill's disease.

# Epidemiology and Demographics
The annual incidence of TN is 4 to 13 per 100,000 people. Despite its low incidence, numbers may be significantly higher due to frequent misdiagnosis. TN is one of the more frequently seen neuralgias in the older adult population. The incidence increases gradually with age; most idiopathic cases begin after age 50, although onset may occur in the second and third decades or, rarely, in children.

# Diagnosis

## Physical Examination
Signs of trigeminal neuralgia can be seen in males who may deliberately miss an area of their face when shaving, in order to avoid triggering an episode. Although trigeminal neuralgia is not fatal, successive recurrences may be incapacitating, and the fear of provoking an attack may make sufferers reluctant to engage in normal activities.

# Treatment

## Medical Therapy
There is no cure for trigeminal neuralgia, but most people find relief from medication or sometimes from one of the many so-called complementary or alternative therapies. Atypical trigeminal neuralgia, which involves a more constant and burning pain, is more difficult to treat, both with medications and surgery. During a TN attack, some patients may get quick relief by applying an ice pack or a readily available source of cold temperature to the area of pain.

## Surgery
There is no cure for trigeminal neuralgia but most people find relief from one of the five surgical options. Surgery may result in varying degrees of numbness to the patient and lead occasionally to "anesthesia dolorosa,"  which is numbness with intense pain. However, many people do find dramatic relief with minimal side effects from the various surgeries that are now available.