"Understanding Cortical Arousals during Sleep from Leg Movements: A Pilot Study."

Leg movements during sleep occur in patients with sleep pathology and healthy individuals. Some (but not all) leg movements during sleep are related to cortical arousals which occur without conscious awareness of the patient but have a significant effect of sleep fragmentation. Detecting leg movements during sleep that are associated with cortical arousals can provide unique insight into the nature and quality of sleep in both health and disease. In this study, a novel leg movement monitor is used in conjunction with polysomnography to better understand the relationship between leg movement and electroencephalogram (EEG) defined cortical arousals. In an approach that we call neuro-extremity analysis, graph theoretic, directed connectivity metrics are used to interrogate the causal links between neural activity measured by EEG and leg movements measured by the sensors within the leg movement monitor. The leg movement monitor in this study utilizes novel capacitive displacement sensors, and a 9-axis inertial measurement unit to characterize leg and foot movements. First, the capacitive displacement measures more closely related to EEG-defined cortical arousals than inertial measurements. Second, the neuro-extremity analysis reveals a temporally evolving connectivity pattern that is consistent with a model of cortical arousals in which brainstem dysfunction leads to near-instantaneous leg movements and a delayed, filtered signal to the cortex. Neuro-extremity analysis reveals causal relationships between EEG and leg movement sensor time-series data that may aid researchers to better understand the pathophysiology of cortical arousals associated with leg movements during sleep.