The significance of the sympathetic nervous system in the pathophysiology of periodic leg movements in sleep.
OBJECTIVE
Periodic leg movements in sleep (PLMS) are frequently accompanied by arousals and autonomic activation, but the pathophysiologic significance of these manifestations is unclear.


METHODS
Changes in heart rate variability (HRV), HRV spectra, and electroencephalogram (EEG) spectra associated with idiopathic PLMS were compared with changes associated with isolated leg movements and respiratory-related leg movements during sleep. Furthermore, correlations between electromyographic activity, HRV changes, and EEG changes were assessed.


METHODS
Sleep laboratory.


METHODS
Whole-night polysomnographic studies of 24 subjects fulfilling the criteria of either periodic leg movements disorder (n = 8), obstructive sleep apnea syndrome (n = 7), or normal polysomnography (n = 9) were used.


RESULTS
Spectral HRV changes started before all EEG changes and up to 6 seconds before the onset of all types of leg movements. An initial weak autonomic activation was followed by a sympathetic activation, an increase of EEG delta activity, and finally a progression to increased higher-frequency EEG rhythms. After movement onset, HRV indicated a vagal activation, and, the EEG, a decrease in spindle activity. Sympathetic activation, as measured by HRV spectra, was greater for PLMS than for all other movement types. In EEG, gamma synchronization began 1 to 2 seconds earlier for isolated leg movements and respiratory-related leg movements than for PLMS. Significant correlations were found between autonomic activations and electromyographic activity, as well as between autonomic activations and EEG delta activity, but not between higher-frequency EEG rhythms and EMG activity or HRV changes.


CONCLUSIONS
These results suggest a primary role of the sympathetic nervous system in the generation of PLMS.
Guggisberg
Adrian G
AG
Center of Sleep Medicine, Department of Neurology, University of Berne, Inselspital, Bern, Switzerland. aguggis@gmail.com
Hess
Christian W
CW
Mathis
Johannes
J
D004569:Electroencephalography; D004576:Electromyography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D020189:Nocturnal Myoclonus Syndrome / Q000175:diagnosis / Q000503:physiopathology*; D017286:Polysomnography; D012720:Severity of Illness Index; D013564:Sympathetic Nervous System / Q000503:physiopathology*