Trigeminal neuralgia

Definition/diagnostic criteria Trigeminal neuralgia (TN) is a debilitating neurological disorder characterised by recurrent and severe facial pain along the distribution of the trigeminal nerve. The pain is typically sudden and excruciating, often described by patients as sharp, stabbing or electric shock-like in nature. It typically affects one side of the face and can be triggered by innocuous stimuli such as chewing, talking or even a gentle touch to the affected area. Diagnosis of TN is primarily clinical.

Epidemiology TN is a relatively rare condition, with an estimated annual incidence of 4-13 per 100,000 individuals in the UK. It predominantly affects individuals over the age of 50, although cases can occur at any age. There is a female preponderance, with a female-to-male ratio of approximately 2:1. The exact cause of TN remains unclear, but it is often associated with vascular compression of the trigeminal nerve root as it exits the brainstem.

Diagnosis
Clinical features:

• Recurrent, unilateral, paroxysmal facial pain.
• Brief duration of pain episodes. The pain lasts for seconds to a few minutes, typically not exceeding two minutes per episode.
• Severe, electric shock-like pain.
• Pain attacks are triggered by non-painful stimuli or specific trigger zones along the trigeminal nerve’s distribution.
• Pain-free intervals occur between the episodes, although they may become less frequent as the condition progresses.

The clinical presentation of TN is distinctive and revolves around the characteristics of facial pain, as described above. The pain typically involves the second (maxillary) and third (mandibular) branches of the trigeminal nerve, sparing the first (ophthalmic) branch. The trigeminal nerve distribution is well delineated, and patients can often point to specific trigger zones on their face.

Investigations: In most cases, a clinical evaluation is sufficient for diagnosing TN. However, if the diagnosis is uncertain or if there are atypical features, further investigations may be warranted.

MRI is the preferred imaging modality to rule out structural abnormalities such as tumours or vascular compression.

Treatment
Pharmacological management: First-line treatment is usually with carbamazepine 100mg 1-2 times a day, titrated every 2 weeks according to response. If carbamazepine is contraindicated, ineffective, or not tolerated, seek specialist advice.

Prognosis TN can have a significant impact on patients’ quality of life due to the recurrent and severe nature of the pain. With appropriate treatment, many patients experience a significant reduction in pain frequency and intensity. However, the condition is often chronic, and long-term management may be necessary.