[The restless leg syndrome: a condition associated with periodic or aperiodic slowing of the EEG]

There are several new developments with regard to semiology, diagnosis, physiopathology and the treatment of restless leg syndrome (RLS). We present here the hypothesis that motor manifestations of the RLS are synchronous to slowing of the cortical activity as measured by the spectral analysis of the EEG. When the subject is resting in bed with his leg outstretched, slowing of the EEG is observed, which could be periodic at the frequency of approximately 1 every 20 seconds or sustained. Leg movements can be periodic at the frequency of approximately 1 every 20 seconds or sustained. Leg movements can be periodic or aperiodic accordingly. On the contrary, periodic leg movements in sleep (PLMS) occur in close temporal relationship with periodic arousal. These results raised the hypothesis that leg movements (RLS and PLMS) may appear at a critical level of cortical activation. This level is reached during sleepiness in the awake subject or during periodic micro-arousal when the subject is asleep. Other results suggest that these periodic changes in the level of cortical activation may also modulate other abnormal motor behavior in sleep such as rhythmic masticatory muscles activity as seen in sleep bruxism. The same mechanism may also be involved in setting the duration of apneic episodes during slow-wave sleep.