SUNCT & SUNA
SUNCT (Short-lasting Unilateral Neuralgiform headache attacks with Conjunctival injection and Tearing) and SUNA (Short-lasting Unilateral Neuralgiform headache attacks with cranial Autonomic symptoms) are rare trigeminal autonomic cephalalgias characterized by very brief, frequent, severe attacks. SUNCT requires both conjunctival injection and tearing; SUNA requires at least one autonomic feature but not necessarily both CIT. These conditions are the most treatment-resistant TACs. They do not respond to indomethacin (unlike PH and HC) or to oxygen/triptans (unlike cluster).
Bottom Line
- Attack profile: Unilateral orbital/temporal stabs lasting 1-600 seconds, occurring 1 to 200+ times per day
- SUNCT: Requires both conjunctival injection AND lacrimation (ipsilateral). SUNA: Requires at least one autonomic feature but not necessarily both CIT.
- No response to indomethacin, oxygen, or triptans — this is a key differentiator from other TACs
- Must exclude trigeminal neuralgia — similar attack pattern but TN has a refractory period and responds to carbamazepine. MRI essential to exclude posterior fossa pathology.
- Treatment: Lamotrigine is first-line (Level C). IV lidocaine for acute exacerbations. Topiramate and gabapentin are second-line.
- Rare condition — most evidence is from case series and expert opinion
ICHD-3 Criteria
SUNCT (3.3.1)
- A. At least 20 attacks fulfilling B-D
- B. Moderate or severe unilateral head pain, orbital/supraorbital/temporal or other trigeminal distribution, lasting 1-600 seconds, occurring as single stabs, series of stabs, or sawtooth pattern
- C. At least one ipsilateral: conjunctival injection AND lacrimation (both required for SUNCT)
- D. Frequency ≥1 attack per day for more than half the time when active
SUNA (3.3.2)
- Same as SUNCT except criterion C requires at least one (not necessarily both) of: conjunctival injection, lacrimation, nasal congestion, rhinorrhea, forehead sweating, miosis, ptosis, eyelid edema
- SUNA is the broader category; SUNCT is the specific subtype with both CIT
Clinical Features
| Feature | Details |
|---|---|
| Pain character | Stabbing, electric shock-like, neuralgiform. Periorbital, temporal, or V1 distribution. |
| Duration | 1-600 seconds (most attacks 5-120 seconds). Three patterns: single stabs, groups of stabs, sawtooth (prolonged). |
| Frequency | Highly variable: 1 to 200+ attacks/day. Severe cases have near-continuous pain with superimposed stabs. |
| Triggers | Cutaneous triggers common: light touch of face, chewing, talking, wind, brushing teeth. Unlike TN, there is no refractory period after triggering. |
| Autonomic features | Conjunctival injection, lacrimation (both in SUNCT). Rhinorrhea, nasal congestion less prominent than in cluster. |
| Demographics | Male predominance. Mean onset age 50 years. Rare (<1% of TACs). |
Differentiating SUNCT/SUNA from Trigeminal Neuralgia
| Feature | SUNCT/SUNA | Trigeminal Neuralgia |
|---|---|---|
| Duration | 1-600 seconds | Typically <2 seconds (single shock) to 2 minutes |
| Autonomic features | Prominent (defining feature) | Minimal or absent (may have mild tearing) |
| Refractory period after trigger | No (attacks can be triggered repeatedly without interval) | Yes (30 seconds to 2 minutes where re-triggering fails) |
| Trigeminal distribution | V1 predominant (periorbital) | V2/V3 predominant (cheek, jaw, teeth) |
| Background pain | Sawtooth pattern with interictal discomfort possible | Typically pain-free between paroxysms |
| Carbamazepine response | Poor or absent | Excellent (diagnostic hallmark of TN) |
| Lamotrigine response | May respond (first-line for SUNCT/SUNA) | Second/third-line |
Mandatory Imaging
- MRI brain with dedicated posterior fossa and pituitary views is required in all patients with SUNCT/SUNA
- Secondary causes have been reported in up to 10-15% of cases: posterior fossa lesions (cerebellopontine angle tumors, epidermoid cysts), pituitary adenomas, vascular malformations, MS plaques
- Consider MRA to evaluate for vascular compression of the trigeminal nerve root (similar to TN etiology)
Treatment
SUNCT/SUNA is the most treatment-resistant TAC. Evidence is limited to case series and expert opinion. Most standard headache treatments are ineffective.
Acute / Exacerbation Management
- IV lidocaine: The only consistently effective acute treatment. Infusion at 1-3 mg/kg/hour under cardiac monitoring. Can suppress attacks within hours. Used as a bridge while transitioning to oral preventive.
- Oxygen, triptans, indomethacin: All ineffective
Preventive Treatment
| Agent | Dose | Evidence | Notes |
|---|---|---|---|
| Lamotrigine | 100-400 mg/day | First-line. Level C. Largest case series (Cittadini 2009): ~60% of patients improved. Blocks voltage-gated sodium channels. | Slow titration required (25 mg × 2 weeks, then 50 mg × 2 weeks, then increase by 50 mg every 2 weeks). Risk of Stevens-Johnson syndrome with rapid titration. HLA-B*1502 testing in patients of Southeast Asian descent. |
| Topiramate | 100-300 mg/day | Level C. Case series show ~50% partial response. | Second-line. Same titration and side effects as in migraine. Can combine with lamotrigine. |
| Gabapentin | 800-3600 mg/day | Level C. Case reports of benefit. | Third-line. Sedation at high doses. May be better tolerated than lamotrigine in elderly. |
| Carbamazepine / Oxcarbazepine | 400-1200 mg/day | Limited and inconsistent. Less effective than in TN. | Worth trying given overlap with TN phenotype. Some patients with SUNA respond better than those with SUNCT. |
| Duloxetine | 60-120 mg/day | Case reports only | Fourth-line option. May address central sensitization component. |
Refractory SUNCT/SUNA
- Combination therapy: Lamotrigine + topiramate, or lamotrigine + gabapentin
- ONS (occipital nerve stimulation): Case series show benefit in refractory SUNCT/SUNA. Implanted neurostimulator. Similar approach as in refractory cluster.
- Microvascular decompression (MVD): If MRA shows vascular compression of the trigeminal nerve, MVD may be curative (same procedure as for TN). Small case series with positive results.
- Gamma knife: Targeting the trigeminal root entry zone. Limited case reports.
Treatment Algorithm for SUNCT/SUNA
- MRI brain (mandatory) to exclude secondary causes
- Lamotrigine titrated to 200-400 mg/day (slow titration over 8 weeks)
- If inadequate: add topiramate or switch to gabapentin
- For acute exacerbations: IV lidocaine as inpatient bridge
- Refractory: occipital nerve stimulation or evaluate for MVD if vascular compression present
References
- Cohen AS, et al. Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) or cranial autonomic features (SUNA): a prospective clinical study of SUNCT and SUNA. Brain. 2006;129(10):2746-2760.
- Cittadini E, Goadsby PJ. Update on SUNCT and SUNA. Expert Rev Neurother. 2011;11(2):241-250.
- Weng HY, et al. SUNCT and SUNA: clinical features, treatments, and outcomes in 74 cases. Cephalalgia. 2018;38(4):679-691.
- Lambru G, et al. SUNCT and SUNA: medical and surgical treatments. Neurol Sci. 2019;40(Suppl 1):S65-S70.