The patient’s unmet needs (PUNs)
A 62-year-old woman attends your emergency clinic in some distress. For the last month she has been experiencing excruciating, unilateral pains in her cheek and mouth. These pains are short lived – lasting a few seconds – and they feel like electric shocks. She says ‘I simply can’t put up with this pain, I can’t eat, brush my teeth or wash my face.’ A brief neurological examination appears normal. You feel sure she has trigeminal neuralgia and explain this to her. ‘How long am I going to have to put up with this?’ she asks. ‘Shouldn’t I have a scan, or see a specialist?’
The doctor’s educational needs (DENs)
What are the diagnostic criteria for trigeminal neuralgia? Which differential diagnoses should I consider?
Trigeminal neuralgia is a unilateral, severe, episodic electric-shock like pain occurring in the distribution of the trigeminal nerve - most commonly in the two lower divisions. Most of the pain attacks are provoked by light touch, for example eating or washing the face. The pain starts suddenly, lasts for less than two minutes and disappears abruptly. It is common for patients to experience 10 to 50 attacks a day, but rarely at night. Classically there is no pain between attacks but some patients will complain of a lingering burning or aching. A diagnosis of trigeminal neuralgia is made on the basis of these symptomatic criteria. The severity of pain in trigeminal neuralgia is such that patient can lose weight and be unable to maintain adequate oral hygiene.
The pain of trigeminal neuralgia is frequently intraoral, so patients often consult a dentist first. Dental pains are a differential diagnosis, and may have similar characteristics, but dental pains are typically triggered by prolonged eating. Dental pains will not usually be felt extra-orally. If the pain is in the first division only then it is unlikely to be trigeminal neuralgia, especially if there are autonomic symptoms during a pain attack which could include ipsilateral red eye or tearing of the eye. These symptoms might suggest a trigeminal autonomic cephalagia. Occasionally, temporomandibular disorders can present as unilateral pain around the ear but the pain is more prolonged than in trigeminal neuralgia and is made worse by prolonged chewing.
What are the current views on the causes of trigeminal neuralgia? To what extent should I investigate these possibilities?
Most trigeminal neuralgia is idiopathic. But magnetic resonance imaging may be of value in determining if there is a neurovascular compression in the cerebello-pontine area, and in a small percentage of patients trigeminal neuralgia is symptomatic because of a tumour (usually benign) or cyst in the posterior fossa, or secondary to multiple sclerosis. Routine neuroimaging computerised tomography or MRI may identify a cause in up to 15% of patients 1.
GPs should refer patients for a scan if they are young, there is bilateral pain, you have a suspicion of MS, there are sensory changes or other neurological finding, or pain that is difficult to control. At some stage all patients with trigeminal neuralgia will require a scan, but this is not needed for diagnosis unless a symptomatic cause is suspected.
Carbamazepine is usually the first line treatment – how effective is this? What dose should we use? And what other options are there?
Carbamazepine is the gold-standard drug and 70% of patients - especially in the early stages - are likely to get complete pain relief within three days. This drug should be started at a low dose dependent on the patient’s weight, and increased every three days. An average dose is 200mg four times daily 2. Carbamazepine has numerous drug interactions and can cause significant side effects, so careful monitoring is important - especially in the first six months or when using higher doses.
If carbamazepine cannot be tolerated change to oxcarbazepine using average doses of 300mg four times a day. There is less evidence for the use of gabapentin or pregabalin 3.
What is the prognosis for trigeminal neuralgia? In a patient on long-term carbamazepine who is asymptomatic, should treatment be reduced or stopped at any stage?
Trigeminal neuralgia is a long-term condition - the periods of pain remission get shorter and the attacks often become longer, but there is no way of predicting this 3. The only patients who remain pain free for long period of time, without requiring drugs, are those who have microvascular decompression surgery. Drug therapy should be continued until patients have been pain-free for at least one month. But if patients relapse once they stop drug treatment they should be referred (rather than staying on treatment indefinitely), as there is some evidence that patients who are operated on early do best.
This condition can have a profound effect on quality of life for the patient and their family and friends. The Trigeminal Neuralgia Association UK, a patient group, can provide support and reduce isolation.
Which patients, with diagnosed trigeminal neuralgia, might require a referral or scan?
Patients who are no longer responding to carbamazepine, who have increasing pain, should be referred for scans and further management. Patients who have classical trigeminal neuralgia and are found to have neurovascular compression can respond well – becoming pain-free - with microvascular decompression which is a major neurosurgical procedure.
Causes
- In most cases cause is unknown, but may be because of tumours, multiple sclerosis, or vascular compression
Epidemiology
- It is a rare disorder, most common around 50-60 years of age with slight predominance of females
Clinical features
- Unilateral, episodic, severe shooting pain in the distribution of the trigeminal nerve provoked by light touch
- Patients rarely have any sensory abnormality
Main differential diagnoses
- Dental pain, temporomandibular pain
Management
- Carbamazepine followed by oxcarbazepine
- Pain diaries
- Provide details of patient support groups
- Neurosurgery
Complications
- Trigeminal neuralgia may have a significant effect on mood and quality of life
- All drugs result in side effects and often drug interactions
Prognosis
- Progressive with time. The best long-term outcomes in classical cases are achieved with neurosurgery.
Professor Joanna Zakrzewska is a consultant and clinical lead for a multidisplinary facial pain unit at University College London Hospital NHS Foundation Trust.
Competing interests: Professor Zakrzewska receives aproportion of funding from the Department of Health’s NIHR Biomedical Research Centre funding scheme and Convergence for running a clinical trial of a new drug in trigeminal neuralgia.
Given that trigeminal neuralgia is so rare, many patients feel isolated. Once they have been diagnosed they then face decisions about whether to continue drug therapy or have major neurosurgery. A support group such as the Trigeminal Neuralgia Association UK can provide patients contact with other patients and with information that has been critically appraised by experts. For more information go to tna.org.uk.
References
1 Cruccu G, Gronseth G, Alksne J et al. AAN-EFNS guidelines on trigeminal neuralgia management. Eur J Neurol ,2008;15(10):1013-28
2 Clinical knowledge summaries. Trigeminal neuralgia. http://www.cks.nhs.uk/trigeminal_neuralgia/management/scenario_diagnosis. Accessed 18.12.12
3 Zakrzewska JM and McMillan R. Trigeminal neuralgia: the diagnosis and management of this excruciating and poorly understood facial pain. Postgrad Med J, 2011;87(1028):410-16
