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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
Key points
- Severe unilateral orbital/supraorbital/temporal pain lasting 15-180 minutes
- Ipsilateral lacrimation, conjunctival injection, rhinorrhea, ptosis, or miosis
- Attacks cluster over weeks and often occur nocturnally
- Acute treatment: 100% oxygen and subcutaneous/intranasal triptan
- Prevention: verapamil first-line
Overview
Cluster headache is a trigeminal autonomic cephalalgia with strictly unilateral severe orbital or temporal pain and ipsilateral autonomic symptoms. Patients are often restless or agitated during attacks, unlike migraine patients who prefer stillness.
Epidemiology
It is less common than migraine, often begins age 20-40, and has male predominance. Alcohol can trigger attacks during an active cluster period. Smoking is strongly associated.
Clinical Features
Symptoms
Excruciating unilateral orbital or temporal pain
Attack duration 15-180 minutes
Ipsilateral tearing, red eye, rhinorrhea, congestion, sweating
Restlessness, pacing, agitation
Persistent painful Horner syndrome outside attacks suggests carotid dissection
Signs
Conjunctival injection and lacrimation ipsilateral to pain
Partial Horner syndrome during attack
Nasal congestion or rhinorrhea
Normal neurological exam between attacks
Persistent neurological signs are atypical
Investigations
First-line
Clinical diagnosisICHD criteria: unilateral severe pain with autonomic symptoms/restlessness
Neurological examinationShould be normal between attacks
Second-line
MRI brain +/- MRAAtypical TAC, abnormal exam, new side-locked headache, poor response
ECGBefore high-dose verapamil escalation
Headache diaryDocuments cluster periodicity and treatment response
Specialist
Movement/headache specialistRefractory or atypical cases
Neuroimaging reviewExclude pituitary, cavernous sinus, and vascular mimics
1
Acute therapy
- 100% oxygen by nonrebreather 12-15 L/min
- Subcutaneous sumatriptan is highly effective
- Intranasal sumatriptan/zolmitriptan alternatives
- Avoid opioids
2
Prevention
- Verapamil first-line with ECG monitoring
- Prednisone or occipital nerve block as transitional therapy
- Lithium for selected chronic cluster
- Galcanezumab may be considered for episodic cluster
3
Triggers/safety
- Avoid alcohol during cluster periods
- Smoking cessation counseling
- Screen for depression and suicidality
- Provide home oxygen when appropriate
4
Refractory treatment
- Specialist referral
- Neuromodulation options in selected cases
- Reassess diagnosis if treatment response poor
Complications
- Severe disability: Pain is extreme
- Depression/suicidality: Screen actively
- Verapamil adverse effects: Bradycardia, heart block, constipation, edema
USMLE Step 2 CK Exam Tips
- 1Unilateral orbital pain + lacrimation/rhinorrhea = cluster headache
- 2Cluster patient paces; migraine patient lies still
- 3Acute treatment = oxygen plus sumatriptan
- 4Prevention = verapamil
- 5Alcohol triggers attacks during cluster periods
- 6Seconds-long facial pain suggests trigeminal neuralgia
- 7Persistent Horner syndrome with neck pain = carotid dissection
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