Cluster Headache Attack Onset
A sudden, severe unilateral headache strikes on a strikingly regular clock.
- 9–10/10: Peak pain intensity (excruciating, often described as suicidal pain)
- ~10 min: Time to peak (rapid crescendo from first twinge)
- 15–180 min: Attack duration untreated (wide range, unpredictable if untreated)
- ~50%: Nocturnal attacks (often same clock hour nightly)
Unilateral periorbital pain
Boring, stabbing pain centers behind or around one eye.
Autonomic signs
Tearing, nasal congestion, ptosis, and facial flushing appear.
Circadian clustering
Attacks recur near the same hour, day after day.
Bouts often bunch around one or two fixed daily times.
High-Flow Oxygen Therapy
100% oxygen at high flow is first-line abortive treatment.
- 12–15 L/min: Flow rate (via non-rebreather mask, seated upright)
- ~15–20 min: Time to relief (most patients report major relief)
- ~70–80%: Response rate (of patients respond within 20 minutes)
- Minimal: Adverse effects (very safe, repeatable per attack)
Delivery method
Non-rebreather mask, seated upright, deep steady breathing.
Proposed mechanism
Cranial vasoconstriction and trigeminal-autonomic reflex dampening.
Effective in most attacks within roughly fifteen to twenty minutes.
Practical advantages
No systemic side effects, safe for frequent daily use.
Injectable Sumatriptan
Subcutaneous sumatriptan offers the fastest pharmacologic abortive option.
- 6 mg SC: Standard dose (self-injected at attack onset)
- ~10–15 min: Time to relief (fastest of all abortive options)
- ~75–96%: Response rate (of attacks respond by 15 minutes)
- 2 injections: Max daily doses (spaced at least one hour apart)
Mechanism of action
5-HT1B/1D agonist constricts cranial vessels, blocks pain signaling.
Onset speed
Subcutaneous route bypasses gut, acts within minutes.
Often faster acting than oxygen, useful when oxygen is unavailable.
Cautions
Avoided with cardiovascular disease; limits doses per day.
Pain Intensity Rapidly Declines
Both abortives produce a steep pain drop versus a slow natural decline.
- ~15–20 min: Oxygen resolution (steep decline curve after mask on)
- ~10–15 min: Sumatriptan resolution (steepest decline of the two options)
- Gradual: Untreated decline (pain lingers for one to three hours)
- Adjunctive: Combination use (oxygen plus injection for refractory attacks)
Treated curve shape
Sharp exponential-style drop once therapy takes hold.
Untreated curve shape
Slow taper, pain persists far longer without treatment.
The gap between treated and untreated curves is the therapy benefit.
Autonomic resolution
Tearing and congestion fade alongside the pain score.
Outcome — Abortion & Bout Recurrence
Most treated attacks abort within thirty minutes, then recur on schedule.
- 15–30 min: Treated abortion window (typical successful abortive response time)
- 15 min–3 hr: Untreated attack length (wide natural range without therapy)
- weeks–months: Bout length (daily attacks cluster into active periods)
- 1–8: Attacks per bout day (often at matching clock hours)
Successful abortion
Pain returns near baseline, autonomic signs resolve fully.
Circadian recurrence
The next attack reappears close to the same hour.
Circadian clustering is a hallmark feature distinguishing this headache type.
Ongoing management
Preventive medication alongside abortives reduces bout burden.