Periodic limb movements are associated with disturbed sleep. Pro.

12 T he significance of periodic limb movements in sleep (PLMS) in the absence of Restless Legs Syndrome (RLS) or Periodic Limb Movement Disorder (PLMD), has been a controversial issue in recent years. Nevertheless, based on evidence gathered in recent years on the associations and consequences of PLMS, the issue needs to be reconsidered.Here it shall be demonstrated, that PLMS are associated with disturbed sleep far beyond the affected individual noticing it, and that they have significant and potentially severe consequences on health, which also extend far beyond subjective sleep impairment. It is well established that PLMS are associated with micro-arousals and autonomic activation and therefore associated with an alteration in sleep structure. Whereas older concepts assumed that PLMS caused those arousals, more recent studies revealed, that PLMS and arousals are associated in another, more complex and non-unidirectional manner: Arousal equivalents, e.g. delta waves, heart rate increases 1 or other changes in cerebral and autonomic activity 2 can herald PLMS. In the most recent scoring criteria for periodic leg movements (PLM), this has been taken into account and a PLM with an arousal can be scored even if the arousal precedes the onset of a PLM. PLM and arousals are not only associated, but might even better be viewed as a common complex, the PLM arousal complex. Terzano and Parrino have described the cyclic alternating pattern (CAP) as a sequence of biphasic cycles reflecting unstable sleep (phase A: activation – phase B: deactivation). 7 CAP A reflects arousal and arousal equivalents. They have demonstrated that in patients with RLS, 92% of all PLM occurred during CAP, and 96% of them during CAP phase A. They conclude that CAP is not the generator of PLM, but acts as a gate control mechanism, phase A representing a permissive window for the occurrence of PLM. 4 Even if PLM co-occur with CAP phase A, not all CAP phase A are associated with PLM. 4 It has been observed that in a sequence of PLM, sometimes leg movements appear to be " missing " , whereas the series of underlying CAP phase A – phase B oscillations continues. 5 This observation indicates that the underlying CAP arousal oscillation is de facto superior to PLM, or that PLM are just a downstream manifestation of the underlying CAP phase A – CAP phase B oscillating mechanism. The latter is generally considered as a measure of unstable …