Clinical Features of Cluster Headache
Cluster headache is characterized by severe unilateral orbital, supraorbital, or temporal pain lasting 15-180 minutes, occurring 1-8 times daily, accompanied by ipsilateral autonomic symptoms and marked restlessness. 1, 2
Pain Characteristics
The hallmark pain is strictly unilateral, severe to excruciating in intensity, and localized to the orbital, supraorbital, and/or temporal regions. 1, 2
- Duration: Each attack lasts 15-180 minutes (not 4-72 hours like migraine), making the attacks relatively brief but intensely severe. 1, 2
- Frequency: Attacks occur with remarkable regularity, ranging from every other day up to 8 times per day during active cluster periods. 2, 3
- Quality: The pain is described as boring, stabbing, or burning rather than throbbing or pulsating. 4
Autonomic Features
At least one ipsilateral autonomic symptom must be present during attacks, which distinguishes cluster headache from other primary headache disorders. 1, 2
The most common autonomic manifestations include:
- Lacrimation (tearing) - the most frequently reported symptom 2, 5
- Conjunctival injection (red eye) 2, 5
- Nasal congestion or rhinorrhea 2, 5
- Ptosis (drooping eyelid) 2, 5
- Eyelid edema 2, 5
- Facial sweating on the forehead or face 2, 5
- Miosis (pupil constriction) 2, 5
Behavioral Features
A sense of agitation or restlessness is pathognomonic for cluster headache and helps distinguish it from migraine. 1, 2
- Patients typically pace, rock back and forth, or exhibit motor restlessness during attacks rather than lying still in a dark room as migraine patients prefer. 1, 5
- This restlessness is so characteristic that its absence should prompt reconsideration of the diagnosis. 5
Temporal Patterns
Cluster headache occurs in two distinct patterns: episodic (80-90% of cases) or chronic. 2, 3
- Episodic cluster headache: Attacks occur in clusters (bouts) lasting weeks to months, followed by remission periods of at least 3 months. 2, 3
- Chronic cluster headache: Attacks occur for more than 1 year without remissions, or with remission periods lasting less than 3 months. 2, 3
- Circadian periodicity: Attacks often occur at the same time each day, frequently awakening patients from sleep 1-2 hours after falling asleep. 4, 5
- Circannual periodicity: Cluster periods often recur at the same time of year in episodic forms. 4
Triggers
Common triggers during active cluster periods include alcohol (even small amounts), nitroglycerin, nitrate-containing foods, and strong odors. 2
- Alcohol is the most reliable trigger during active cluster periods but typically does not trigger attacks during remission. 2
- Vasodilators like nitroglycerin can provoke attacks. 2
Distinguishing Features from Other Headaches
Cluster headache differs from migraine by its shorter duration (15-180 minutes vs. 4-72 hours), strictly unilateral location with autonomic symptoms, and patient restlessness rather than preference to lie still. 1
- Unlike migraine, cluster headache lacks prominent nausea/vomiting and photophobia/phonophobia as primary features. 1
- Unlike tension-type headache, cluster headache is strictly unilateral (not bilateral), severe (not mild-moderate), and has prominent autonomic features. 1, 6
Epidemiology
- Prevalence is less than 0.1% of the population, making it a rare disorder. 2, 3
- Mean age of onset is 30 years. 2
- Male predominance of 2-3:1. 2
- Diagnostic delay averages 7 years, with frequent misdiagnosis as migraine or sinusitis. 3
Critical Diagnostic Pitfall
Before diagnosing cluster headache, neuroimaging (preferably MRI brain) is warranted to exclude structural mimics, particularly in atypical presentations or new-onset cases. 7, 4