Trigeminal neuralgia is neuropathic pain in the distribution of the trigeminal nerve.

Episodes of paroxysmal shooting or sharp natured pain occur typically provoked by stimuli such as light touch, eating, washing, talking or air currents on the face. Patients may describe 'electric shock-like pain'. Pain is more common in the maxillary (V2) and mandibular (V3) divisions of the trigeminal nerve than the ophthalmic division (V1). It is more frequently seen in patients over 50-years-old and in those with multiple sclerosis but can occur in young adults. It is typically unilateral, although may be bilateral in multiple sclerosis.

The cause is not always known. Many patients are found to have an aberrant vascular loop compressing the nerve on MRI scan. Other potential causes include micro-vascular aneurysms, tumours, arachnoid cysts in the cerebellopontine angle or secondary to traumatic events such as car accidents.

There are no specific investigations to diagnose trigeminal neuralgia. However, clinical assessment of cranial nerve function should be carried out due to the association with multiple sclerosis and also brain tumours. Any abnormalities should prompt cerebral imaging. There is an argument for cerebral imaging in all patients as MRI can be used to detect vascular compression of the trigeminal nerve near the pons. If this is the case micro-vascular decompression of the aberrant vessel provides immediate pain relief in approximately 75% of patients.

Cluster headaches are classically felt as a deep dull aching pain in the retrobulbar, cheek and chin area lasting several hours.

Giant cell arteritis is commonly felt as a continuous pain the forehead, temple and neck area and may be associated with jaw claudication.

Atypical facial pain may occur in any area and be of various characteristics.

Post-herpetic neuralgia is the persistence of pain in the affected dermatomes, after the resolution of an acute herpes zoster infection (shingles). The diagnosis is usually made if pain persists or arises at least three months after the skin lesions are healed. The commonest areas affected are in the thoracic dermatomes and the ophthalmic division of the trigeminal nerve.