Exoskeleton-assisted gait in chronic stroke: An EMG and functional near-infrared spectroscopy study of muscle activation patterns and prefrontal cortex activity

Objectives: Gait impairment dramatically affects stroke patients' functional independence. The Ekso™ is a wearable powered exoskeleton able to improve over-ground gait abilities, but the relationship between the cortical gait control mechanisms and lower limbs kinematics is still unclear. Our aims are: to assess whether the Ekso™ induces an attention-demanding process with prefrontal cortex activation during a gait task; to describe the relationship between the gait-induced muscle activation pattern and the prefrontal cortex activity. Methods: We enrolled 22 chronic stroke patients and 15 matched controls. We registered prefrontal cortex (PFC) activity with functional Near-Infrared Spectroscopy (fNIRS) and muscle activation with surface-electromyography (sEMG) during an over-ground gait task, performed with and without the Ekso™. Results: We observed prefrontal cortex activation during normal gait and a higher activation during Ekso-assisted walking among stroke patients. Furthermore, we found that muscle hypo-activation and co-activation of non-paretic limb are associated to a high prefrontal metabolism. Conclusions: Among stroke patients, over-ground gait is an attention-demanding task. Prefrontal activity is modulated both by Ekso-assisted tasks and muscle activation patterns of non-paretic lower limb. Further studies are needed to elucidate if other Ekso™ settings induce different cortical and peripheral effects. Significance: This is the first study exploring the relationship between central and peripheral mechanisms during an Ekso-assisted gait task.