EEG arousals and awakenings in relation with periodic leg movements duringsleep

It is known that periodic leg movements are frequently accompanied by full awakenings or by signs of EEG arousals. The time relationship of these EEG arousals with leg movements varies from patient to patient. They may preced e or follow leg movements or occur simultaneously. It is not clear whether these arousals trigger leg movements or, alternatively, whether both EEG ar ousals and leg movements are separate expressions of a common pathophysiolo gical mechanism. We investigated the temporal relationship of five EEG arou sals, such as alpha activity, K-complexes, spindles, K-alpha, K-spindle act ivities and awakenings, with leg movements in 10 periodic leg movement pati ents. These EEG arousals were considered to be associated with leg movement s if they occurred 10 s before/after or simultaneously with the onset of ri ght or left tibialis muscle EMG potentials. It was found that 49.19% of EEG arousals occurred before leg movements, 30.61% occurred simultaneously and 23.18% occurred just after leg movements. The number of EEG arousals was s ignificantly higher in the 10 s preceding leg movement than simultaneously or in the 10 s following. Alpha activity was the phenomenon associated most frequently with leg movements, irrespective of its temporal organization a nd was significantly higher during the 10 s preceding movement. Spindle and K-spindle activities were significantly higher before leg movement, wherea s K-complex activity was significantly more frequent during leg movements. The number of awakenings was significantly higher after leg movements than simultaneously. These results indicated that leg movements are not primary, but rather are a phenomenon associated with an underlying arousal disorder .