Clinical Features of Hemicrania Continua
Hemicrania continua is characterized by continuous, strictly unilateral headache with ipsilateral cranial autonomic symptoms during exacerbations and an absolute response to indomethacin. 1
Core Clinical Presentation
Pain Characteristics
The hallmark feature is persistent, unilateral background headache that is continuous and side-locked in 92% of patients 1. The background pain typically:
- Ranges from mild to moderate intensity (mean 6.5/10 on verbal rating scale)
- Has an oppressive or burning quality
- Remains strictly on one side (though 8% may have side-alternating pain) 1
Exacerbation Pattern
Superimposed on the continuous baseline pain are severe exacerbations that 1:
- Last an average of 32 minutes (range highly variable)
- Reach severe to excruciating intensity (mean 9/10, with 71% rating pain as excruciating)
- Have a predominantly stabbing quality
- Occur with unpredictable frequency
Associated Symptoms During Exacerbations
Cranial Autonomic Features
97% of patients experience at least one cranial autonomic symptom during pain exacerbations 1. The most common include:
- Lacrimation (73%) - most frequent autonomic feature
- Nasal congestion (51%)
- Conjunctival injection (46%)
- Ptosis and facial flushing (40% each)
- Rhinorrhea, forehead/facial sweating, eyelid edema
- Less common: aural fullness, periaural swelling, miosis, mydriasis, facial/cheek swelling 1
Migrainous Features
Contrary to typical trigeminal autonomic cephalalgias, hemicrania continua frequently presents with migraine-like symptoms 2:
- Phonophobia (79%) - unilateral in 48% of cases
- Photophobia (74%) - unilateral in 48% of cases
- Motion sensitivity (69%)
- Nausea and vomiting during exacerbations 3, 1
Behavioral Features
Restlessness or agitation occurs in approximately two-thirds of patients during severe exacerbations, with about one-quarter becoming verbally aggressive 1, 3. This restlessness is now included in diagnostic criteria and helps distinguish hemicrania continua from other headache disorders.
Temporal Pattern
- Chronic form (82%): Unremitting pain without remission periods >3 months
- Episodic form (18%): Pain remissions lasting >3 months between active periods
Diagnostic Sine Qua Non
Complete response to therapeutic doses of indomethacin is mandatory for diagnosis 3, 1, 2. This response is:
- Absolute and dramatic (not partial)
- Demonstrable via placebo-controlled indomethacin test (100-200 mg intramuscularly) or oral trial
- The defining feature that separates hemicrania continua from all other headache disorders 1
Common Diagnostic Pitfalls
Misdiagnosis is Extremely Common
The most frequent misdiagnoses are 2:
- Migraine - due to presence of photophobia, phonophobia, nausea, and unilateral pain
- Cluster headache - due to severe exacerbations with autonomic features
Key Distinguishing Features
What clinicians often miss 2:
- The persistent featureless background headache between exacerbations - patients and physicians focus only on severe attacks
- The strictly unilateral, side-locked nature (pain never switches sides in 92% of cases)
- The continuous daily presence of some degree of pain
Clinical Recognition Strategy
For any patient with unilateral headache (with or without cranial autonomic symptoms), consider an indomethacin trial 1. The diagnosis is frequently missed even by headache specialists because:
- Variable exacerbation duration and frequency mimic other conditions
- Background pain may be dismissed as insignificant
- Migrainous features deflect from the correct diagnosis 2
Epidemiology
Hemicrania continua accounts for approximately 1.8-2% of patients evaluated in tertiary headache clinics 3, 4, making it uncommon but not rare. The mean age of onset is 46 years, with female predominance (28 females to 8 males in one series) 4.