Contactless detection of periodic leg movements during sleep: A 3D video pilot study

Abstract

In clinical practice, the quality of polysomnographic recordings in children and patients with neurodegenerative diseases may be affected by sensor displacement and diminished total sleep time due to stress during the recording. In the present study, we investigated if contactless three-dimensional (3D) detection of periodic leg movements during sleep was comparable to polysomnography. We prospectively studied a sleep laboratory cohort from two Austrian sleep laboratories. Periodic leg movements during sleep were classified according to the standards of the World Association of Sleep Medicine and served as ground truth. Leg movements including respiratory-related events (A1) and excluding respiratory-related events (A2 and A3) were presented as A1, A2 and A3. Three-dimensional movement analysis was carried out using an algorithm developed by the Austrian Institute of Technology. Fifty-two patients (22 female, mean age 52.2 ± 15.1 years) were included. Periodic leg movement during sleep indexes were significantly higher with 3D detection compared to polysomnography (33.3 [8.1-97.2] vs. 30.7 [2.9-91.9]: +9.1%, p = .0055/27.8 [4.5-86.2] vs. 24.2 [0.00-88.7]: +8.2%, p = .0154/31.8 [8.1-89.5] vs. 29.6 [2.4-91.1]: +8.9%, p = .0129). Contactless automatic 3D analysis has the potential to detect restlessness mirrored by periodic leg movements during sleep reliably and may especially be suited for children and the elderly.

Keywords: arousal; automatic movement detection; polysomnography; restless sleep; video.

Figure 1

(a) Setup of the three‐dimensional (3D) sensor above the bed in the sleep laboratory. (b) Graphic example of the comparison of 3D and polysomnography (PSG) recordings. Left: images created by the 3D sensor. Top: near‐infrared video. Bottom: colour‐coded motion detection (red = motion). Right: time course of 3D and PSG signals. 3D Legs: 3D‐detected leg motion. Tib L, Tib R: electromyography (EMG) signals from left and right m. tibialis anterior. C4: central electroencephalogram (EEG) channel. Hypnogram: indicates sleep stage (rapid eye movement [REM] ‐ phase 5). Movement at 01:31:51 (red line): anteflexion of the toe, movement clearly visible in PSG video and in 3D, no detection in EMG of tibialis anterior (TA) muscles. Movement at 01:32:00 (green line): dorsiflexion of the toe, movement clearly visible in PSG video and in 3D, detection also in EMG of TA muscles. [Videos can be viewed at www.sleepmotionanalyzer.com.]

Figure 2

Intermovement interval (IMI) histogram of leg movements during non‐rapid eye movement (REM) sleep in all 52 patients. Panel A shows the IMI distribution for version A1, panel В shows the IMI distribution for version A2 and panel С reports the IMI distribution of version A3