The trigeminal nerve is the largest of the cranial nerves, providing sensory input to the skin of the face and anterior half of the head, teeth, oral and nasal cavities. It has limited motor component to the muscles of mastication. The nerve divides into 3 major divisions: the ophthalmic, the maxillary, and the mandibular nerves. The mandibular division is the largest of the 3, and its motor component supplies the muscle of mastication.2

Incidence
Trigeminal neuralgia is more common in women and is seen almost exclusively in persons older than 40 years and most often, between the ages of 50 and 69 years. Attacks are more common on the right side of the face.

Etiology
Trigeminal neuralgia is most often idiopathic in origin. It could be a symptom of central nervous system disease; other causes are:  secondary to compression of the sensory root adjacent to the pons by a tumor, an enlarged superior cerebellar or anterior inferior cerebellar arteries, or by pontine branches of the basilar artery or vein or arteriovenous malformations.2 Such compression can lead to demyelination of the nerve root.3 Uncommonly it could be a presentation of multiple sclerosis and should be suspected when trigeminal neuralgia occurs in a young person.4

Pathophysiology
The mechanism of pain production has been controversial. As per one theory, peripheral injury or disease of the trigeminal nerve increases afferent firing in the nerve. There may be associated failure of the central inhibitory mechanism as well. Pain is perceived when nociceptive neurons in a trigeminal nucleus involve thalamic relay neurons.4 Studies indicate that trigeminal neuralgia is usually caused by demyelination of trigeminal sensory fibers within either the nerve root or less commonly, the brainstem.5 The cause of pain is explained by the ignition hypothesis. According to the hypothesis, trigeminal neuralgia results from specific abnormalities of trigeminal afferent neurons in the trigeminal root or ganglion. Injury renders the axons hyperexcitable. The hyperexcitable afferents, in turn, give rise to pain paroxysms as a result of synchronized after-discharge activity.6

Natural History
Though spontaneous remission is common, over time, the disorder is progressive and the pain becomes more severe and more frequent, requiring higher dosage and more continuous use of medications.8
Diagnosis
Diagnosis of trigeminal neuralgia is based exclusively on history, symptoms, and normal neurological examination results. Trigeminal neuralgia is characterized by brief episodes of severe pain in the face. The pain usually lasts for a few seconds to a minute or 2. It is usually limited to one division of the trigeminal nerve and more often to the right side of the face. The mandibular and maxillary divisions of the trigeminal nerve are more often involved than the ophthalmic division. Eating, speaking, or touching specific sites in the face, such as occurs while shaving or brushing teeth, can act as a trigger. The patient is usually pain-free between episodes. The patient's face may contort with pain depending on its severity; hence, the name "tic douloureux."

Differential Diagnosis
Other causes of facial pain from local facial structures and pain from neuralgia have to be considered in the differential diagnosis. A syndrome similar to trigeminal neuralgia can be caused by acoustic neuroma, aneurysms, trigeminal neuromas, and meningiomas. These conditions should be considered, particularly if the patient is younger than 40 years and has pain predominantly in the forehead and eye (ophthalmic division of trigeminal nerve), when the pain is bilateral, or there is evidence of bilateral sensory loss or associated motor signs such as weak jaw, facial weakness, or swallowing difficulty.7

Diagnostic Studies
Diagnostic studies may be necessary when the condition occurs in a younger person or when the presentation is atypical. Magnetic resonance imaging (MRI) and 3-dimensional fast-in-flow with steady-state precession MRI may help to determine the presence of tumors or plaques of multiple sclerosis.1 It will also help to assess possible compression and deformation of the trigeminal nerve.

MRI neuroimaging using the technique called 3-D volume acquisition with contrast injection can detect an offending vascular loop causing compression on the nerve 80% of the time

 Dr Harshad Raval MD [Homeopathy]
Honorary consultant homeopathy physician to his Excellency Govern.of Gujarat India.
Qualified MD consultant homeopath Physician,
Member of nominee advisory committee (Govt. of Gujarat).
International Homeopathy Advisor, Book writer and Columnist For Gujarat Samachar,   ADDRESS:16,floor,white-House| Ellishbridge | Ahmedabad | Gujarat | India
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