Periodic leg movements are part of the B-wave rhythm and the cyclic alternating pattern

Abstract

Periodic leg movements (PLM) in sleep are supposed to constitute a frequent cause of insomnia. There is some controversy whether PLM are the cause of insomnia by provoking microarousals or whether they are simply and epiphenomenon not casually related to the insomnia. We examined four patients with PLM by overnight polysomnography and concomitant transcranial Doppler sonography (TCD) monitoring, 13 patients with suspected normal pressure hydrocephalus by concomitant overnight polysomnography and intracranial pressure recording, and 10 healthy volunteers by concomitant overnight polysomnography and TCD monitoring. EEG arousals occurred more frequently before than after the PLM. PLM were associated with increase in heart rate, breathing amplitude, and cerebral blood flow velocity assessed by TCD. PLM occurred with a mean wavelength of 40.5 s. This mean wavelength corresponded to similar values calculated for intracranial pressure B-waves (43.3 s) in 13 patients with suspected normal-pressure hydrocephalus, TCD B-wave equivalents (42.2 s) in 10 healthy young adults and the frequency of the cyclic alternating pattern in EEg recordings (40 s). Our date suggest that these cyclic variations with a wavelength of about 40 s are part of a common endogenous rhythm. PLM seem to be an epiphenomenon of this rhythm and not the cause of insomnia.

The Mozart Effect

“…Parrino et al (32) reported that the longest periods were 31 seconds in older subjects. The CAP is now considered to be related to bruxism (33), nocturnal paroxysmal dystonia (34), myoclonic seizures (35), and periodic leg movements (36). Thus, the CAP, as an integrating mechanism for the central nervous system, represents an intrinsic periodic change every 20 -40 seconds and stimuli that vary at that same frequency or period may resonate with this intrinsic patterning to produce beneficial effects within the brain.…”

Animal studies in restless legs syndrome

“…There is evidence that PLM are modulated by another periodic sleep phenomenon called the cyclic alternating pattern (CAP) of sleep. [4][5][6] Furthermore, CAP rates seem to be increased in RLS patients (personal communication with R. Ferri). As there is an analogue to CAP that can be analyzed in rats 7,8 changes in the microstructural aspects of sleep-wakefulness cycle could become a feature analyzed in an animal model of RLS.…”

Does Restless Legs Syndrome increase cardiovascular risk in Attention-Deficit/Hyperactivity Disorder?

“…To our knowledge, CAP in patients with RLS/PLMS has been assessed only in few studies [24][25][26]. Ferri et al [24] analyzed adults with RLS/PLMS and reported that CAP analysis revealed a significantly higher NREM sleep instability in RLS patients, with approximately 75% of this stage occupied by CAP sequences [24].…”

“…The increase of NREM sleep instability accompanying the RLS/ PLMS activity might also be accompanied by an increased sympathetic output as an epiphenomenon of a disrupted endogenous rhythm that comprises EEG arousals, EEG slow oscillations (CAP) and variability of heart rate and respiration [2,26,27].…”