Episodic cluster headache: NREM prevalence of nocturnal attacks. Time to look beyond macrostructural analysis?

A high prevalence of nocturnal sleep-related attacks is reported in patients with cluster headache (CH). Episodic CH is considered closely related to rapid eye movement (REM) sleep.

The aim of this study was to analyze the relationships between episodic CH attacks and sleep macrostructure.

Data were obtained by means of 24-hour continuous ambulatory polysomnography (PSG) capturing CH attacks in 4 out of 7 episodic CH patients (all males; mean age 38.4 +/- 9.2 years) studied.

Eight CH attacks were captured during the PSG monitoring; 5 arose from sleep: 4 from non-rapid eye movement (NREM) sleep (stage 2 NREM), and 1 from REM sleep. One patient experienced CH attacks during both NREM and REM sleep in the same night.

In the light of previous literature findings, the prevalence of NREM-related episodic CH attacks observed, and the finding of attacks arising during both REM and NREM sleep in the same subject, suggest that the relationship between CH and sleep stages is heterogeneous, and the existence of a specific macrostructural pattern associated with episodic CH attacks appears to be uncertain. A more comprehensive approach taking into account the microstructure of NREM and REM sleep is expected to provide more in depth information about the pathophysiology of CH, whose complexity might overcome the simplistic dichotomy of REM/NREM staging.