Abstract WMP85: Recovery Rate vs. Recovery Capacity: A Mathematical Model and its Implications for Rehabilitation
INTRODUCTION: Recovery of most hemiparetic patients at 90 days can be well predicted as a fixed proportion (70%) of initial motor deficit. However, recent work has shown considerable variability in the rate of recovery among proportional recoverers, prompting consideration of whether rate of recovery and recovery capacity are independent and whether a single rate dynamic governs proportional recovery.
HYPOTHESIS: Among proportional recoverers, recovery rate variability can be accounted for by a single mathematical model in which: 1) recovery rate is independent of recovery capacity and 2) recovery has a sigmoid trajectory parameterized only by initial stroke severity.
METHODS: We studied 23 patients with first-ever unilateral hemiparetic stroke previously identified as proportional recoverers. Fugl-Meyer Upper Extremity Motor Exam (FM-UE) had been measured at <72h, 1 week, and 90 days. A non-linear model predicting patients’ FM-UE score at any time after stroke onset was posited and model parameters were estimated by regressing one-week FM-UE scores against initial scores. Statistical significance and goodness of fit were evaluated.
RESULTS: The model accounted for 86% of variability in motor recovery achieved by patients at 1 week after stroke onset (pseudo-R2=0.863, F23,21=418.0, p<.0001) and predicted that more severely impaired patients will have a slower maximum recovery rate and a recovery period that is longer in duration and more delayed in onset.
CONCLUSION: The model provides evidence that proportional recovery is governed by a single rate dynamic and that recovery rate is independent of recovery capacity. It provides a tool for predicting motor impairment at any time following stroke onset and suggests a framework for characterizing the biology of recovery and the role of therapeutic interventions as either capacity-enhancing or rate-enhancing.
- © 2012 by American Heart Association, Inc.