Changes in serial correlation coefficients and fractional parameters during functional recovery in stroke patients

This study attempted to determine changes in motor unit discharge patterns, characterized by serial correlation coefficients (SCC) and fractional parameters during a functional recovery in stroke patients. Using the surface electrode technique, 171 single motor units were recorded from bilateral upper extremities of 23 stroke patients and 7 normal volunteers. SCCs and fractional parameters were calculated and correlated with Rasch-converted Functional Independence Measurement (FIM) scores by linear regression analysis. No statistically significant correlation was found between FIM scores and SCCs and between FIM scores and fractional parameters recorded during first four weeks post stroke. Only FIM for total motor scores and FIM for locomotion subscore significantly correlated with SCC recorded after 4 weeks post stroke (p < 0.05). Predictive power (R²) of SCC for FIM scores did not change much over time. Fractional parameters, recorded after 4 weeks post stroke, had significant correlation with FIM for total motor scores and all FIM subscores except FIM for sphincter control subscores. Predictive values of fractional parameters for FIM scores was better after 6 months post stroke. There was a better correlation between fractional parameters with FIM scores and a better predictive value of fractional parameters for FIM scores over functional recovery period. This change in the correlation during the course of stroke recovery may indicate that fractional parameters could reflect a more stabilized motor control stage rather than a less stabilized motor functional stage.