SUNCT Syndrome

SUNCT syndrome is short lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing. Attacks are brief, severe, frequent and strictly unilateral, usually in the orbital or temporal region.

It is very rare, with a prevalence of about 1 in 100,000. It starts at a mean age of about 50 years, with a male predominance (about 2:1).

Pattern of attacks. Attacks last 1 to 600 seconds, occur from 1 to 200 or more each day, and may be single stabs, groups of stabs, or a saw tooth pattern. They are triggered by cutaneous stimuli (touch, chewing, washing) with no refractory period.

Secondary causes. Posterior fossa lesions, pituitary tumours, trigeminal neurovascular compression, vascular lesions and brainstem disease are reported, so careful imaging is needed.

Pathophysiology.

Trigeminal autonomic reflex activation with posterior hypothalamic involvement causes attacks and cranial autonomic signs.

Trigeminal nerve root compression may be the trigger in some patients.

• Brief stabbing, burning or shooting pain in the orbital, supraorbital or temporal region, lasting 1 to 600 seconds, often with a frequency of 3 to 200 each day.
• Marked ipsilateral conjunctival injection and lacrimation, with other features such as nasal congestion, rhinorrhoea or eyelid oedema.
• Cutaneous triggers in the trigeminal area, and attacks with neck movement.
• No response to indomethacin, which distinguishes it from other trigeminal autonomic cephalalgias.

Red flags.

• Neurological deficit, sensory loss, papilloedema or visual symptoms.
• Onset in a young person or progressive course.
• Pituitary hormone abnormality.

• ICHD-3 criteria: at least 20 attacks of moderate to severe unilateral pain lasting 1 to 600 seconds, with both conjunctival injection and lacrimation, occurring at least once daily for more than half the time.
• MRI of the brain with contrast, with attention to the pituitary, posterior fossa and trigeminal nerve; MR angiography for neurovascular compression.
• Pituitary hormone testing when there is any pituitary abnormality.
• Headache diary of attack frequency and duration; exclude trigeminal neuralgia.

Differential diagnosis. SUNA, trigeminal neuralgia, paroxysmal hemicrania, cluster headache, hemicrania continua, secondary headache from posterior fossa or pituitary lesions.

• Preventive drugs are required because attacks are brief and untreatable once started; acute drugs are not effective.
• Lamotrigine, first line: 25 mg orally once daily for 2 weeks, then 50 mg daily for 2 weeks, then increases of 50 mg every 1 to 2 weeks to a usual 100 to 200 mg daily in 2 divided doses. Maximum 400 mg daily. Monitor for rash, hypersensitivity and Stevens-Johnson syndrome (stop at the first rash). Reduce dose in moderate to severe hepatic impairment; reduce the titration rate with valproate; levels fall with oestrogen containing contraception and in pregnancy.
• Topiramate 25 mg orally at night, increased by 25 mg weekly to a usual 100 to 200 mg daily in 2 divided doses. Maximum 400 mg daily. Review at 3 months and stop if there is no benefit. Monitor bicarbonate, mood, weight, kidney stones and visual symptoms. Halve the dose when creatinine clearance is under 70 mL/min; contraindicated in pregnancy and effective contraception is needed.
• Gabapentin 300 mg orally at night on day 1, 300 mg twice daily on day 2, then 300 mg three times daily on day 3, increased by 300 mg every 3 to 7 days to 900 to 2400 mg daily in 3 divided doses. Maximum 3600 mg daily. Review at 4 to 8 weeks and stop if there is no meaningful benefit. Monitor sedation, dizziness, peripheral oedema, mood and misuse. Adjust for renal function: creatinine clearance 50 to 79 mL/min, 600 to 1800 mg daily; 30 to 49 mL/min, 300 to 900 mg daily; 15 to 29 mL/min, 150 to 600 mg daily; under 15 mL/min, 150 to 300 mg daily. Avoid in pregnancy unless benefit outweighs risk.
• Greater occipital nerve block, and neuromodulation or intravenous therapy at a specialist centre, for refractory attacks.
• Surgical or neuromodulatory options (microvascular decompression, occipital nerve stimulation) for selected refractory patients with neurovascular compression.
• Treat secondary causes found on imaging.

Monitoring. Review at 4 to 6 weeks and every 3 months; track attack frequency; check for rash and drug effects.

Referral and escalation. Headache specialist for all patients; neurosurgery for neurovascular compression or lesion.

Special groups. Pregnancy: avoid topiramate, and plan treatment with specialists. Older adults: slower titration and lower doses of gabapentin.