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Introduction
Trigeminal Neuralgia (TN, or TGN) is a neuropathic condition involving dysfunction of the Trigeminal Nerve, the fifth cranial nerve, which provides both sensory and motor innervation to large portions of the face. It is characterised by enormous localised pain experienced by patients, the incredibly and incapacitating nature of which has given the condition the nickname “Suicide Disease”, and lead to it being described clinically as one of the most painful conditions in modern medicine.

Anatomy/Neural Connectivity of the Condition:
The bilaterally paired Trigeminal Cranial Nerve (CN V) branches into three divisions, consisting of V1 (The Opthalmic Nerve); V2 (The Maxillary Nerve) and V3 (The Mandibular Nerve). These branches correspond to three dedicated skin dermatomes for sensory innervation, as demonstrated in Figure 1. [1]

In regards to motor innervation, the Trigeminal Nerve’s motor root stimulates four unilateral muscles of mastication, including the masseter, the temporalis, and both medial and lateral pterygoid muscles. The condition itself can be attributed to the existence of a lesion of the sensory nuclei, root, or intradermal branches of the Trigeminal Nerve. This can sometimes be caused by an incidence of Multiple Sclerosis, or malformation of Epidermoid cysts which stretch the Trigeminal Nerve root. Much more commonly, the condition is thought to be caused by the principle of Neurovascular Compression. Although still poorly understood in the field of modern medicine, Neurovascular Compression involves compression of the microvasculature of the trigeminal nerve by an abnormally enlarged blood vessel (believed to be the superior cerebellar artery, primarily) near the location of connection between CN V and the Pons. This is shown in Figure 2.

How the Condition Functions/Pathology:
Continued compression of the trigeminal nerve, vascular or otherwise, will result in segmental demyelination of the Trigeminal Nerve root. This leads to hyperactivity and erratic stimulation of the nerve itself as well as its innervated musculature. Intervals of severe pain can thus be created by a variety of external stimulus, including mechanical pressure, temperature change, and movement of the tongue, facial and mastication muscles. The pain experienced during these intervals can be excruciating, being present for cycles of months or years before going into remission for similar periods of time.

Recent Innovations in Treatment:
A variety of medications are used to treat the condition, including the anticonvulsant Carbamazepine, and pain medication such Lidocaine, Morphine and low doses of antidepressants such as Tryptizol. There are, furthermore, two other innovative options for treatment of Trigeminal Neuralgia. Although these treatments have been available for several years, new studies have shown that they may be more effective than first thought. In a recent study of Microvascular Decompression (a procedure designed to treat Trigeminal Neuralgia by surgically reducing vascular pressure in offending arteries) it was found that 91% of the 141 patients studied experienced a lack of symptoms in the twelve months following the procedure. Within five years of the procedure, this success rate remained surprisingly high at 76%. Furthermore, new developments in three dimensional MRI imaging technology have been found to greatly assist in the diagnosis of TN and procedural accuracy of Microvascular Decompression.

References:
[1] Leclercq D, Thiebaut JB, Héran F. (2013) “Trigeminal neuralgia”.Diagn Interv Imaging. Retrieved 22-09-2013.

[2] Prasad, S, Galetta, S (2009). "Trigeminal Neuralgia Historical Notes and Current Concepts". Neurologist 15 (2): pp87–94. Retrieved 22-09-2013.

[3] http://www.nlm.nih.gov/cgi/mesh/2011/MB_cgi?mode=&term=Masticatory+Muscles. Accessed 22/09/13

[4] Babu R, Murali R (1991). "Arachnoid cyst of the cerebellopontine angle manifesting as contralateral trigeminal neuralgia: case report". Neurosurgery28 (6): 886–7

[5] José Lorenzonia, Philippe Davidb, Marc Levivierc, (2012) "Patterns of neurovascular compression in patients with classic trigeminal neuralgia: A high-resolution MRI-based study .” European Journal of Radiology. Volume 81, Issue 8, Pp 1851–1857

[6] Okeson, JP (2005). In Lindsay Harmon. Bell's orofacial pains: the clinical management of orofacial pain. Quintessence Publishing Co, Inc. p. 115.

[7] Sindrup, SH; Jensen, TS (2002). "Pharmacotherapy of trigeminal neuralgia".Clin J Pain 18 (1): 22–7.

[8] Hodaie M. Coello A. F. (2013) “Advances in the management of trigeminal neuralgia” 57(1):13-21

[9] Jo KW, Kong DS, Hong KS, Lee JA, Park K. (2013) “Long-term prognostic factors for microvascular decompression for trigeminal neuralgia.” 20(3):440-5.