The significance of the sympathetic nervous system in the pathophysiology of periodic leg movements in sleep

Sleep. 2007 Jun;30(6):755-66. doi: 10.1093/sleep/30.6.755.


Study objectives: Periodic leg movements in sleep (PLMS) are frequently accompanied by arousals and autonomic activation, but the pathophysiologic significance of these manifestations is unclear.

Design: 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.

Setting: Sleep laboratory.

Patients: 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.

Measurements and 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.

MeSH terms

  • Electroencephalography
  • Electromyography
  • Female
  • Heart Rate / physiology
  • Humans
  • Male
  • Middle Aged
  • Muscle, Skeletal / physiopathology
  • Nocturnal Myoclonus Syndrome / diagnosis
  • Nocturnal Myoclonus Syndrome / physiopathology*
  • Polysomnography
  • Severity of Illness Index
  • Sympathetic Nervous System / physiopathology*