Revised criteria from the third edition of the International Classification of Headache Disorders (ICHD-3), which reclassifies period of chronic cluster headache (CCH) from <1 month to <3 months, can differentiate between CCH and episodic cluster headache (ECH) and may increase the number of CCH diagnoses. This is according to results of a study published in PLoS One.

Data from the multicenter Korean Cluster Headache Registry (KCHR), which enrolled consecutive patients with cluster headache and probable cluster headache aged ≥19 years (n=250), was used for this study. Criteria A to E of the ICHD-3 code 3.1 were used to identify the diagnosis of cluster headache. Using the ICHD-3, the researchers investigated clinical features of CCH as well as the clinical features of CCH based on remission periods and onset patterns.

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Among patients with cluster headache who had a definitive remission period (n=188), the frequency of CCH was 4.6%. Of the 12 patients with CCH, 50.0% had a remission period of <1 month, whereas the other half had a remission period of 1 month to 3 months. A total of 6 patients with CCH had this headache type from time of cluster headache onset. Conversely, CCH had evolved from ECH in the other 50% of patients.

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Patients with CCH had a median age of 41.5 years, and 16.7% (n=2) were women. The most common region of cluster headache pain was the supraorbital area in 83.3%, and the most common associated symptom was conjuntival injection (91.7%)

In participants with CCH, the age of onset of cluster headache was significantly older than those with ECH (38.0 vs 24.0 years, respectively; P =.003). The number of years following the onset of cluster headache was lower in patients with CCH vs those with ECH (2.5 vs 10.0, respectively; P <.001). Current smoking was associated with secondary CCH vs ECH (66.7% vs 45.9%, respectively; P =.025). Compared with secondary ECH, the number of years following cluster headache onset were less in secondary CCH (10.0 vs 5.5, respectively; P =.041).

The reports of location of pain and frequency of accompanying symptoms were not significantly different between patient with CCH and those with ECH, with the exception of nasal congestion and/or rhinorrhea. Results also demonstrated that the total number of episodes of headache was significantly lower among patients with CCH who had a remission period of < 1 month compared with those who had a remission period of 1 to 3 months (6.0 and 17.5, respectively).

Limitations of the study included its cross-sectional design, potential recall bias as a result of patient-described clinical courses in the classification of ECH and CCH, and the lack of assessment of the frequency of smoking and alcohol consumption.

The researchers suggested their findings indicate “the proportion of patients with CCH diagnosis may increase with the use of ICHD-3 [and] some clinical features of CCH were different from those of ECH.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Cho SJ, Lee MJ, Kim BK, et al. Clinical features of chronic cluster headache based on the third edition of the International Classification of Headache Disorders: A prospective multicentre study. PLoS One. 2019;14(8):e0221155.