Cluster Headache: A Bedside Diagnosis of the "Suicide Headache"

Dr Neeraj Manikath , claude.ai

Abstract

Cluster headache (CH) represents one of the most severe pain syndromes known to medicine, yet remains a purely clinical diagnosis made at the bedside. This review synthesizes current understanding of CH for postgraduate trainees in internal medicine, emphasizing the pathognomonic clinical features that render imaging and laboratory investigations unnecessary. We explore the diagnostic pearls, common pitfalls ("oysters"), and practical management strategies that every internist should master when confronted with this dramatic presentation.

Introduction

Cluster headache has been described as "the worst pain known to humanity"—a statement supported by patients who have experienced childbirth, renal calculi, and traumatic injuries, yet rank CH as more severe.1,2 The term "suicide headache" is not hyperbolic; studies document significantly elevated suicide rates among CH sufferers compared to the general population.3 Despite its devastating impact, CH affects only 0.1% of the population, contributing to frequent misdiagnosis and treatment delays averaging 5-7 years.4

The internist's greatest diagnostic tool for CH is not the MRI scanner or laboratory panel, but rather careful observation and pattern recognition. This article emphasizes why CH diagnosis belongs entirely at the bedside and provides the clinical framework necessary for confident identification.

Why ONLY Bedside? The Case Against Routine Neuroimaging

The Paradox of Normal Investigations

Cluster headache presents a fascinating paradox: the severity of symptoms is inversely proportional to objective findings. Neuroimaging (MRI or CT) is characteristically normal.5 Routine laboratory studies reveal nothing. The electroencephalogram shows no abnormalities. This disconnect between subjective agony and objective normalcy is itself a diagnostic clue.

Pearl #1: If your patient describes the worst headache of their life occurring repeatedly in identical fashion, and the MRI is normal, think cluster headache, not "reassuring results."

When to Image: The Red Flags

While CH diagnosis is clinical, neuroimaging is indicated when atypical features suggest secondary causes:

• New-onset CH after age 50 (consider temporal arteritis, structural lesions)
• Change in established attack pattern or character
• Abnormal neurological examination
• Failure to respond to appropriate abortive therapy
• Strictly posterior location (occipital)6

Secondary cluster-like headaches can result from pituitary adenomas, cavernous sinus lesions, arteriovenous malformations, and carotid dissections.7 These, however, represent the rare exceptions that prove the rule.

Oyster #1: A 55-year-old patient presenting with their first "cluster-like" headache had a pituitary macroadenoma. Age matters—true primary CH typically begins between 20-40 years.

The Definitive Clinical Picture: Five Cardinal Features

1. The Pain Character: "Suicide Headache"

The pain quality separates CH from all other headache disorders. Patients use vivid, violent metaphors:

• "A hot poker through my eye"
• "Ice pick stabbing my temple"
• "Someone drilling into my skull"
• "My eye being pulled out from behind"8

The pain is:

• Severity: 10/10 on pain scales, incapacitating
• Location: Strictly unilateral, orbital, supraorbital, and/or temporal
• Laterality: Fixed to one side during a cluster period (though may switch sides between cluster periods)
• Quality: Boring, piercing, stabbing—never throbbing

Pearl #2: If the patient can calmly describe their headache while seated comfortably in your office, it's probably not a cluster headache. CH patients in an active attack appear tormented.

2. Duration: The 15-180 Minute Window

Unlike migraine (4-72 hours) or tension-type headache (variable), CH attacks have a characteristic temporal profile:

• Rapid onset: Reaches maximum intensity within 5-10 minutes
• Duration: 15-180 minutes if untreated (this is an ICHD-3 diagnostic criterion)9
• Rapid resolution: Pain disappears as quickly as it arrived
• Frequency: 1-8 attacks per day during cluster periods (often 1-3 daily)

Pearl #3: Ask, "How long does each attack last?" If they say "hours to days," reconsider your diagnosis. If they say "30-90 minutes, then it's completely gone," you're looking at CH.

The typical patient experiences attacks with clock-like regularity—often awakening from sleep 90 minutes after falling asleep (during REM sleep) or occurring at the same time daily.10

Hack #1: The "alarm clock headache"—attacks at 1 AM, 2 PM daily—is so characteristic that patients can predict their attacks. This circadian rhythm points directly to hypothalamic involvement.

3. Autonomic Symptoms: The Ipsilateral Symphony

CH is the only trigeminal autonomic cephalalgia (TAC) where autonomic features are mandatory for diagnosis. These symptoms occur ipsilateral to the pain and include at least one of:11

Cranial Autonomic Features:

• Conjunctival injection and/or lacrimation (88% of patients)12
• Nasal congestion and/or rhinorrhea (76%)
• Eyelid edema (63%)
• Forehead and facial sweating (60%)
• Miosis and/or ptosis (Horner's syndrome, 57%)
• Facial flushing or sensation of aural fullness

The combination of excruciating pain plus autonomic symptoms creates the pathognomonic "red, weeping eye" presentation.

Pearl #4: The autonomic symptoms help distinguish CH from trigeminal neuralgia. TN has stabbing pain but no lacrimation or conjunctival injection.

Oyster #2: A patient presented with unilateral orbital pain and ipsilateral ptosis/miosis but no lacrimation or nasal symptoms. This persistent Horner's syndrome led to discovery of carotid dissection—always examine for complete vs. partial Horner's.

4. Restlessness and Agitation: The Behavioral Signature

This feature is perhaps the most dramatic and diagnostically specific. Unlike migraine patients who seek dark, quiet rooms and remain still, CH patients exhibit:

• Inability to remain seated or lie down
• Pacing, rocking, or moving constantly
• Pressing or rubbing the affected area
• Banging their head against walls (severe cases)
• Agitation, sometimes appearing aggressive13

Pearl #5: The "pacing sign"—observing your patient unable to sit still in the waiting room or examination room during an attack—is virtually pathognomonic for CH.

One study found that 93% of CH patients exhibited restlessness during attacks compared to only 3% of migraine patients.14 This behavioral difference reflects the neurobiological distinction between these disorders.

Hack #2: Ask family members, "What does the patient do during the headache?" If they describe frantic pacing or rocking, you have your diagnosis before the patient finishes speaking.

5. Circadian and Circannual Periodicity: The Temporal Signature

CH demonstrates remarkable temporal patterns that reflect hypothalamic dysfunction:

Circadian Pattern:

• Attacks occur at predictable times of day
• Peak incidence: 1-2 hours after sleep onset and 1-3 PM15
• Seasonal transitions (spring/fall) often trigger cluster periods

Circannual Pattern (Episodic CH, 80-90% of cases):

• Cluster periods last 2 weeks to 3 months (typically 6-12 weeks)
• Followed by remission periods lasting months to years (average 1 year)
• Same time of year annually for many patients16

Chronic CH (10-20% of cases):

• Attacks occur for >1 year without remission, or with remissions lasting <3 months
• May evolve from episodic CH or begin de novo

Pearl #6: Episodic clustering is so characteristic that patients often recognize when a cluster period is beginning ("I can feel it coming on"). This anticipatory awareness should prompt immediate preventive therapy initiation.

The Physical Examination: What You Will (and Won't) Find

During an Active Attack

If fortunate (or unfortunate) enough to examine a patient during an attack, you will observe:

• Obvious distress, inability to remain still
• Ipsilateral autonomic signs: ptosis, miosis, tearing, conjunctival injection, nasal discharge
• Normal neurological examination otherwise
• No photophobia or phonophobia (unlike migraine)
• Patient may be pressing the affected area or applying cold/heat

Hack #3: Photograph the patient during an attack (with consent). The image of a red, weeping eye with ptosis alongside documented pain timing creates powerful clinical documentation.

Between Attacks

The interictal examination is entirely normal. This normalcy includes:

• Full extraocular movements
• Normal pupillary responses (unless chronic Horner's has developed)
• Normal visual fields and acuity
• No papilledema
• Normal motor and sensory examination

Oyster #3: A persistent Horner's syndrome between attacks can occur in chronic CH but should prompt consideration of structural causes, especially if CH is new-onset.

Differential Diagnosis: Not Everything That Hurts Is Cluster

Other Trigeminal Autonomic Cephalalgias (TACs)

Paroxysmal Hemicrania:

• Similar to CH but shorter duration (2-30 minutes)
• More frequent attacks (>5 per day, often 10-20)
• Absolutely responsive to indomethacin (diagnostic test)
• More common in women17

SUNCT/SUNA:

• Very short duration (5 seconds to 4 minutes)
• Very high frequency (3-200 per day)
• Prominent conjunctival injection and tearing
• Poor response to standard CH treatments18

Hack #4: If attacks last <15 minutes with very high frequency, consider paroxysmal hemicrania and trial indomethacin 150 mg daily for 3 days. Complete response confirms diagnosis.

Migraine with Autonomic Features

Some 20-30% of migraines have autonomic symptoms, but differentiating features include:

• Longer duration (hours, not minutes)
• Photophobia and phonophobia
• Nausea/vomiting more prominent
• Prefer to lie still in dark room
• Female predominance (CH is 3-4:1 male predominance)19

Trigeminal Neuralgia

• Electric shock-like quality (not boring/stabbing)
• Trigger zones (touching face, chewing)
• Very brief episodes (seconds)
• No autonomic symptoms
• Older age of onset typically

Clinical Pearls: Mastering the Bedside Diagnosis

Pearl #7: The "CATCH" mnemonic for CH diagnosis:

• Circadian/Circannual pattern
• Autonomy (autonomic symptoms)
• Terrible pain (10/10)
• Cannot remain still (restlessness)
• Half the head (strictly unilateral)

Pearl #8: Ask about alcohol: 50-70% of CH patients report alcohol as a trigger during cluster periods (but not during remission). This is so specific that some patients use alcohol as a diagnostic test.20

Pearl #9: The "rebound after remission" phenomenon: If a patient reports that attacks stopped for months, then suddenly returned with the same pattern, this circannual periodicity is virtually diagnostic.

Pearl #10: Gender and smoking: Despite being more common in men, CH is increasingly diagnosed in women. Historically, 90% of CH patients smoked, though this association is weakening. However, smoking history remains a positive likelihood ratio.21

Diagnostic Pitfalls: The Oysters

Oyster #4: Silent sinus syndrome mimicking CH—A patient with "cluster headache" had subtle enophthalmos and maxillary sinus opacification on imaging. Silent sinus syndrome can cause orbital pain with ipsilateral autonomic features. Always examine both eyes carefully for symmetry.

Oyster #5: Medication overuse complicating diagnosis—Chronic daily headache from triptans or analgesic overuse can mask underlying CH. If the pattern is obscured by daily medication use, consider a supervised withdrawal period to reveal the true attack pattern.

Oyster #6: Bilateral symptoms suggesting something else—While pain is unilateral, some patients experience contralateral "shadow pain" or minor autonomic symptoms. True bilateral simultaneous severe pain is not CH and requires imaging to exclude serious pathology.

Management Principles: Beyond Diagnosis

While comprehensive management exceeds this review's scope, internists should know:

Abortive Therapy:

• High-flow oxygen (12-15 L/min via non-rebreather, 15 minutes): 70-80% effective, first-line22
• Subcutaneous sumatriptan 6 mg: 75% effective within 15 minutes23
• Intranasal zolmitriptan 5-10 mg: Effective when oxygen unavailable

Hack #5: Patients often don't know about oxygen therapy. Prescribing home oxygen can be life-changing and is without significant side effects.

Preventive Therapy (Transitional and Maintenance):

• Verapamil 240-960 mg daily (first-line, requires EKG monitoring)
• Prednisone burst for rapid cluster breaking
• Lithium, topiramate, or melatonin as alternatives24

Hack #6: For acute cluster period onset, combine: (1) prednisone 60-80 mg daily for 5 days, then taper; (2) verapamil 240 mg daily, increased weekly; (3) home oxygen. This "triple therapy" bridge provides rapid relief while verapamil reaches therapeutic levels.

The "Test" You Cannot Order: Clinical Observation

The most powerful diagnostic tool for CH is direct observation. The constellation of:

1. Visible agony and restlessness
2. Red, weeping eye with ptosis
3. Temporal pattern consistent with typical attacks
4. Normal examination between attacks

...creates a clinical picture so distinctive that experienced clinicians diagnose CH within minutes of observation.

Pearl #11: If possible, have patients record video during home attacks. Modern smartphones allow documentation that brings the bedside to your office. Watching a patient's distress, autonomic symptoms, and restlessness on video often clinches the diagnosis.

Conclusion

Cluster headache remains a bedside diagnosis precisely because its clinical features are so stereotypical and dramatic that no investigation can add diagnostic certainty. The internist who masters recognition of CH's five cardinal features—excruciating unilateral orbital pain, 15-180 minute duration, ipsilateral autonomic symptoms, restlessness, and circadian/circannual periodicity—requires no imaging to make the diagnosis confidently.

The tragedy of CH is not diagnostic complexity but rather diagnostic delay from unfamiliarity with its presentation. Every internist should be able to recognize the pacing patient with the red, weeping eye and initiate effective therapy immediately. In doing so, we provide not just symptomatic relief but potentially life-saving intervention for a condition that truly earns its moniker as the "suicide headache."

Key Takeaways for the Postgraduate

1. CH diagnosis is clinical; normal imaging is expected, not reassuring
2. The five cardinal features are sufficient for diagnosis
3. Observe for restlessness—the behavioral signature that distinguishes CH from migraine
4. Ask about temporal patterns—circadian and circannual periodicity are diagnostic
5. Initiate oxygen therapy immediately—it's effective, safe, and often unknown to patients
6. Consider secondary causes only with atypical features or abnormal examination
7. The "test" is watching your patient suffer—no laboratory can replicate this diagnostic tool

Final Pearl: Cluster headache is one of the few conditions where being present during an attack makes the diagnosis obvious. If you're uncertain, ask the patient to return during their next predicted attack time. What you observe will resolve all doubt.

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