Onset of nocturnal attacks of chronic cluster headache in relation to sleep stages

Nocturnal attacks are symptomatic of numerous primary headache syndromes. It has proven possible to verify, with polygraphic sleep recordings, a strict correlation between the onset of headache attacks and the rapid eye movements (REM) stage for migraineurs, patients with chronic paroxysmal hemicrania and cluster headache (CH). The purpose of this study was to investigate the correlation between attack onset of chronic CH and sleep stages, the REM stage in particular. Nine patients from our headache outpatient service with a diagnosis of CH were examined in this study. All medication was discontinued at least one week prior to sleep polygraphias, which were conducted in a sleep laboratory on two consecutive nights. Any attacks were treated with oxygen inhalation during the drug-free period. EEG, EMG, and EOG were continuously monitored during the sleep polygraphias. Eight patients had 25 CH attacks during 12 of the 17 nights recorded. Only three of these patients had arousals with attacks in the REM stage and these amounted to five of the 25 recorded attacks. Eleven attacks were in stage 2, four in stage 1 and two in stage 3. These results correlate with recent findings according to which headache attacks were often related to REM in episodic CH, but rarely in the chronic type. Whether or not different pathogenic mechanisms are involved in the episodic and the chronic type of CH is a matter for further discussion.