Computer detection and analysis of periodic movements in sleep

Validation of a leg movements count and periodic leg movements analysis in a custom polysomnography system

BACKGROUND

Periodic leg movements (PLM) during sleep (PLMS) are considered strongly related to restless legs syndrome (RLS), and are associated with polymorphisms in RLS risk genes. Various software for automatic analysis of PLMS are available, but only few of them have been validated. Aim of this study was to validate a leg movements count and analysis integrated in a commercially available polysomnography (PSG) system against manual scoring.

METHODS

Twenty RLS patients with a PLMS index > 20/h and 20 controls with a PLMS index < 5/h were included. Manual and computerized scoring of leg movements (LM) and PLM was performed according to the standard American Academy of Sleep Medicine (AASM) criteria. LM and PLM indices during sleep and wakefulness, the rate of PLMS associated with respiratory events, intermovement interval and periodicity indices were manually and automatically scored.

RESULTS

The correlation between manual and computerized scoring was high for all investigated parameters (Spearman correlation coefficients 0.751-0.996, p < 0.001; intraclass correlation coefficients 0.775-0.999, p < 0.001). Bland-Altman plots showed high agreement between manual and automatic analysis.

CONCLUSIONS

This study validated an automatic LM count and PLM analysis against the gold standard manual scoring according to AASM criteria. The data demonstrate that the software used in this study has an outstanding performance for computerized LM and PLM scoring, and LM and PLM indices generated with this software can be reliably integrated in the routine PSG report. This automatic analysis is also an excellent tool for research purposes.

Blink reflex excitability is abnormal in patients with periodic leg movements in sleep

The excitability of the late component of the blink reflex was measured in 19 patients with periodic leg movements in sleep (PLMS) and in 18 control patients with other sleep complaints. PLMS patients were not different from controls regarding age, body mass index, and apneas and hypopneas per hour of sleep. The latencies of the R1 and R2 components of the blink reflex were not different between the groups. However, in PLMS, the excitability of the R2 response was markedly enhanced: The second R2 response to a pair of stimuli given at an interval of 500 ms was in PLMS 59.5% (range 21-87%) of the first R2 response and in controls 18.8% (range 2-79%) (p < 0.0001, Mann-Whitney U test). These results provide further evidence of an altered motor control in PLMS, which is likely to be located subcortically and possibly related to the dopaminergic striatopallidal system.