Background: Animal models of brain recovery identify the first days after lesioning as a time of great flux in sensorimotor function and physiology; these findings have implications for human stroke recovery. After rodent motor system lesioning, daily skill training in the less affected forelimb reduces skill acquisition in the more affected forelimb. We asked whether spontaneous human motor behaviors of the less affected upper extremity (UE) early after stroke resemble the animal training model, with the potential to suppress clinical recovery.
Methods: This prospective observational study used a convenience sample of patients <7 days after stroke (n=25) with a wide severity range; Controls were hospitalized for non-neurological conditions (n=12). Outcome measures were Accelerometry, Upper-Extremity Fugl-Meyer (UEFM), Action Research Arm Test (ARAT), Shoulder Abduction/ Finger Extension Test (SAFE), NIH Stroke Scale (NIHSS).
Results: Accelerometry indicated total paretic UE movement was reduced compared to controls, primarily due to a 44% reduction of bilateral UE use. Unilateral paretic movement was unchanged. Movement shifted to unilateral use of the nonparetic UE, which increased by 77%. Low correlations between movement time and motor performance prompted an exploratory factor analysis (EFA) revealing a 2-component solution; motor performance tests load on one component (motor performance) whereas accelerometry-derived variables load on a second non-orthogonal component (quantity of movement).
Conclusions: Early after stroke, spontaneous overall UE movement is reduced, and movement shifts to unilateral use of the nonparetic UE. Thus, spontaneously-arising UE motor behaviors early after stroke are potential substrates for two mechanisms associated with poorer motor outcomes in animal models: learned non-use and inhibition of motor recovery through training of the nonparetic side. Accurate UE motor assessment requires two independent constructs: motor performance and quantity of movement. These findings provide opportunities and measurement methods for studies to develop new behaviorally-based stroke recovery treatments that begin early after onset.