Fig. 2
From: Debate: Are cluster headache and migraine distinct headache disorders?
Chronobiologic rhythms. Cluster headache (CH) shows specific chronobiological features, mainly circadian (most frequently nocturnal) and circannual rhythms. In episodic CH, the attacks appear in a series of daily attacks lasting for weeks or months (cluster bout) followed by a complete remission for months or years. Migraine attacks rarely affect sleep and frequently occur during the day. Although migraine patients experience periodicity in attack frequency and severity [15], the periodicity of migraine attacks is not prominent compared to CH attacks