Non-reflex mediated changes in plantarflexor muscles early after stroke

Abstract

The aims of this study were to determine whether changes in the non-reflex component of spastic plantarflexors had developed 2 and 4 months after stroke and to study their relationship with the level of impairment. One group of adults with hemiparesis (HPs) was tested 2 and 4 months after the onset of stroke, and data were compared with a control group (CTLs) tested once. Twenty-two patients (14 males) admitted over a 4-month period in a rehabilitation centre (mean = 62 yrs +/- 14), and 11 (6 males) non-disabled (CTLs) subjects (mean = 57yrs +/- 12.8) agreed to participate in the study. The resistive torque (RT) recorded with a myometer during slow (8-10 degrees/s) passive dorsiflexions imposed manually served as the primary outcome, whereas, the Ashworth score (spasticity), ankle ROM and Fugl-Meyer motor subscore were used as secondary measures to determine the level of impairment. The mean RT values measured at 0 degrees dorsiflexion on the affected and unaffected sides were compared with those in CTLs. As expected, the RT values 2 and 4 months post-stroke on the unaffected side did not differ from corresponding values in CTLs. Significantly higher RT values on the affected side when compared to the unaffected side were found both at 2 months (39%; p < 0.05) and at 4 months (43%; p < 0.01). No significant difference existed on the affected side between the 2nd and 4th months. A high (r = 0.80) and significant (p < 0.0001) correlation coefficient was calculated between the changes in RT values recorded at 2 and 4 months. Low and not significant correlations were computed between these RT changes and factors such as the ROM (r = -0.24), the Ashworth score (r = 0.23) and the Fugl-Meyer lower extremity motor subscore (r = -0.26). Present results indicate that: (1) changes in the non-reflex component are already present 2 months after stroke but do not increase significantly between the 2nd and 4th months; (2) these changes are not related to the level of impairment; and (3) myometry testing at 2 months could be used as a preventive measure to detect patients more at risk of developing severe passive muscle stiffness.