Neuropathic and Neurovascular Orofacial Pain
What you must know
Classify neuropathic orofacial pain: trigeminal neuralgia (paroxysmal, electric shock-like, triggered by touch, cold, or chewing in a V2/V3 distribution), painful post-traumatic trigeminal neuropathy (after extraction or implant, with sensory change), burning mouth disorder, and postherpetic neuralgia. Know neurovascular entities: migraine with aura, and the rare but critical giant cell arteritis and carotid dissection presentations.
Key distinctions
Trigeminal neuralgia has pain-free intervals and a trigger zone; it is not continuous. Post-traumatic neuropathy has altered sensation and constant or evoked pain in the injured nerve territory. Burning mouth disorder occurs in the absence of mucosal disease and is often associated with psychosocial factors; it is not the same as a nutritional deficiency, though deficiencies should be excluded. Neurovascular pain is often throbbing and may be associated with autonomic or neurologic signs.
Traps
Do not diagnose trigeminal neuralgia when pain is constant or accompanied by sensory loss - that suggests a secondary cause or neuropathy. Carbamazepine is first-line for classic trigeminal neuralgia; gabapentinoids and tricyclics are more typical for neuropathic pain. Burning mouth is not treated with antifungals unless candidiasis is documented. Red flags in trigeminal neuralgia include young age, sensory loss, and bilateral symptoms, which warrant imaging.
Worked example
A 60-year-old has 5-second electric shocks in the right cheek when brushing teeth, with symptom-free intervals. This is classic trigeminal neuralgia; carbamazepine is first-line. If the patient had constant burning and numbness after a molar extraction, the diagnosis would instead be painful post-traumatic trigeminal neuropathy.
Rule of thumb
Paroxysmal + trigger + pain-free intervals = neuralgia. Constant + sensory change + injury history = neuropathy.