Predicting improvement in the upper paretic limb after stroke: a longitudinal prospective study

A number of longitudinal studies show that about one third of all patients regain dexterity following a stroke. However, the determinants of improvement of upper limb function are largely unknown. The aim of the present study was to investigate the longitudinal relationship of functional change in the upper paretic limb and change in time-dependent covariates in order to develop a multivariable regression model to predict improvement in dexterity.

Based on 18 repeated measurements over time during the first post-stroke year, 101 stroke patients with first-ever ischemic middle cerebral artery strokes were investigated. Baseline characteristics as well as longitudinal information from Action Research Arm Test (ARAT), Fugl-Meyer arm and hand score (FM-arm and FM-hand), Motricity Index arm and leg score (MI-arm and MI-leg), letter cancellation task (LCT), Fugl-Meyer balance score (FM-balance) and progress of time were obtained prospectively. Outcome constituted of change scores on the ARAT over first year post stroke. Adjoining measurements of time-dependent variables were used to calculate time-dependent changes producing change scores.

In total 1570 of the 1717 change scores were available for longitudinal regression analysis. The regression model shows that FM-hand change scores was the most important relative factor in predicting improvement on ARAT (standardized beta=0.357; p<0.001) followed by change scores on FM-arm (beta=0.007; p<0.001), whereas progress of time was significantly negatively associated with improvement on ARAT (beta=-0.001; p<0.001).

Functional improvement of the upper paretic limb is mainly determined by improvement of the paretic hand, followed by synergistic independent movement of the paretic arm. Progress of time itself is an independent covariate that is negatively associated with upper limb function suggesting that most pronounced improvements occur earlier after stroke.