Cluster headache

Cluster headache is a primary headache disorder that causes severe, strictly one-sided pain usually around the eye or temple, lasting 15 minutes to 3 hours when untreated. Attacks often occur in “clusters” — periods of weeks to months with frequent daily headaches, followed by remission periods that can last months or years. During a cluster period, attacks may happen at the same time each day, including during sleep.

Cluster headache is less common than migraine but is among the most painful headache conditions. It is more frequent in men. Acute treatments such as high-flow oxygen and injectable or nasal triptans can stop attacks quickly. Preventive medicines and, in refractory cases, advanced therapies reduce attack frequency during cluster periods.

Typical features of a cluster attack include:

• Excruciating pain on one side of the head, often focused behind or around one eye, the temple, or the forehead
• Pain that reaches full intensity quickly
• Restlessness or agitation — people often pace or rock rather than lie still (unlike many migraine attacks)
• Same-side autonomic signs: red or watery eye, drooping eyelid, constricted pupil, runny or blocked nostril, forehead sweating, or facial flushing
• Attacks lasting 15–180 minutes untreated
• Frequency from every other day up to eight times a day during a cluster period
• Circadian pattern — often at night or at predictable times

Episodic cluster headache includes remission periods of at least 3 months; chronic cluster headache has remissions shorter than 3 months or none for at least a year.

The exact cause is not fully known. Cluster headache involves the trigeminal-autonomic reflex and hypothalamic activation, which helps explain the circadian and circannual patterns. Genetics contribute in some families. Smoking is strongly associated. Unlike migraine, cluster headache is not primarily driven by the same cortical spreading-depression pathways, though some people have both conditions. Alcohol commonly triggers attacks during an active cluster period but not during remission.

Risk factors include:

• Male sex
• Age 20–50 at onset (can occur at any adult age)
• Smoking or prior tobacco use
• Family history of cluster headache
• History of head trauma in some studies
• Possible associations with sleep apnea

Complications are mainly related to the impact of repeated severe pain:

• Sleep disruption and daytime fatigue
• Anxiety and depression
• Medication overuse if acute treatments are used too frequently without prevention
• Impaired work and social functioning during cluster periods
• Rarely, injury related to severe agitation during attacks
• Side effects from preventive or acute medications

You cannot fully prevent the disorder, but you can reduce attack burden:

• Avoid alcohol during an active cluster period
• Maintain a regular sleep schedule; treat sleep apnea if present
• Do not smoke; seek help to quit
• Use prescribed preventive medication at the start of a cluster period as directed
• Keep acute treatments (oxygen, triptan) accessible for rapid use

Diagnosis is clinical, based on International Classification of Headache Disorders criteria: severe unilateral orbital/temporal pain, attack duration and frequency, ipsilateral autonomic features, and restlessness. A detailed headache diary helps. MRI of the brain is often performed once to exclude secondary causes, especially at first presentation or with atypical features. Differential diagnosis includes migraine, paroxysmal hemicrania, SUNCT/SUNA, trigeminal neuralgia, and secondary trigeminal autonomic cephalalgias.

See a clinician for severe one-sided headaches, especially with eye redness, tearing, or restlessness. First-ever severe headache, headache with fever, neurologic deficits, or a change in a previously stable pattern needs prompt evaluation to exclude secondary causes. A neurologist or headache specialist can confirm the diagnosis and optimize acute and preventive therapy.

Treatment has two goals: stop individual attacks and suppress the cluster period.

Acute (abortive) treatment

• High-flow oxygen (100% oxygen via non-rebreather mask at 12–15 L/min for 15–20 minutes) — safe and effective for many
• Sumatriptan injection or nasal spray; zolmitriptan nasal spray
• Noninvasive vagus nerve stimulation in some regions as an option
• Avoid relying solely on oral triptans or ordinary painkillers — they are usually too slow

Preventive treatment (started early in a cluster period)

• Verapamil — commonly used first-line preventive (requires ECG monitoring at higher doses)
• Corticosteroids (short course) as transitional prevention while longer-term agents take effect
• Lithium, topiramate, galcanezumab (in some regions for episodic cluster), and others in selected patients
• Occipital nerve blocks as transitional therapy
• For refractory chronic cluster: neuromodulation (occipital nerve stimulation, deep brain stimulation in specialized centers), or other advanced options

Practical steps during a cluster period:

• Keep oxygen equipment and/or injectable/nasal triptan ready and use at the first sign of an attack
• Avoid alcohol completely until the cluster period ends
• Maintain regular sleep times; avoid afternoon naps if they trigger attacks
• Take preventive medicine consistently
• Track attack times, triggers, and treatment response
• Seek support — cluster headache can be isolating; patient organizations can help
• Do not drive or operate machinery during an attack

Bring:

• A headache diary (timing, duration, side, autonomic features, treatments tried)
• Photos or notes about eye redness, tearing, or eyelid changes during attacks
• List of medicines and prior preventive trials
• Questions about oxygen prescription, verapamil monitoring, and specialist referral