Clinical case
An elderly patient describes sudden paroxysms of excruciating, stabbing, electric shock-like pain confined to one side of the face, lasting only seconds to minutes. Attacks are triggered by touching a small area of skin, a draught of cold air or toothbrushing, but there is no pain between attacks and no numbness. Examination reveals no objective sensory loss and no dental or other organic cause, and the pain is abolished by carbamazepine, confirming the diagnosis.
Pathophysiology
The cause is unknown, but central compression of the trigeminal nerve is thought to contribute. When trigeminal neuralgia arises in multiple sclerosis, demyelination of the spinal trigeminal nucleus is thought to be responsible. The maxillary (Vb) or mandibular (Vc) divisions are usually affected and pain comes to involve both; the ophthalmic (Va) division is rarely affected and the pain does not spread to the opposite side.
Epidemiology and Risk Factors
Non-modifiable | Modifiable |
|---|---|
Elderly age | No modifiable risk factors |
Multiple sclerosis as an underlying cause (found in 3–4% of atypical cases; 2–3% of 'classical' cases) | |
Affects the maxillary and mandibular divisions predominantly |
Clinical Features
Symptoms | Signs |
|---|---|
Paroxysmal facial pain | Trigger zones |
Severe excruciating pain | Absence of objective sensory loss |
Stabbing pain | Refractory period after triggering |
Electric shock-like pain | No detectable organic cause |
Pain lasting seconds to minutes | |
Unilateral pain | |
Pain-free between attacks | |
Trigger-evoked pain |
Investigations
Primary investigations:
Clinical history (diagnosis readily made on typical features)
Exclusion of dental causes such as pulpitis or diseased teeth (including radiographs)
Gold standard investigation:
Diagnosis is clinical, based on the history; abolition of the pain by an anticonvulsant such as carbamazepine helps to confirm the diagnosis.
Investigations to consider:
MRI if there are atypical features or suggestion of other nerve involvement (particularly to exclude multiple sclerosis)
Differential diagnosis
Condition | Distinguishing features |
|---|---|
Multiple sclerosis | The most important differential; suspected when there are atypical features or other neurological deficits, usually in younger patients, and demyelination of the spinal trigeminal nucleus is the cause. |
Pulpitis / dental pain | Pulpitis is identified by the patient as toothache of a different character; inflamed pulp pain soon becomes more prolonged rather than remaining paroxysmal and lightning-like. |
Atypical trigeminal neuralgia | Shows more continuous, longer-lasting burning or aching pain with an absence of trigger periods, unlike the paroxysmal trigger-evoked pain of typical trigeminal neuralgia. |
Temporomandibular pain dysfunction syndrome | Trigeminal neuralgia may be misdiagnosed as pain dysfunction syndrome when triggered by mastication, but the quality of the pain is quite different (severe, paroxysmal and stabbing). |