Ipsilesional Arm Aiming Movements After Stroke: Influence of the Degree of Contralesional Impairment

Abstract

The authors examined the effects of the degree of impairment of the contralesional upper limb and the side of the hemispheric damage on ipsilesional upper limb performance in chronic stroke individuals. Right- and left-side stroke resulting in mild-to-severe impairment and healthy participants took part in simple and choice reaction time tasks involving aiming movements. The stroke individuals performed the aiming movements with the ipsilesional upper limb using a digitizing tablet to ipsi- or contralateral targets presented in a monitor. The global performance of the group with severe right hemispheric damage was worse than that of the other groups, indicating that the side of hemispheric damage and degree of motor impairment can adversely affect aiming movement performance.

Relationship Between Motor Capacity of the Contralesional and Ipsilesional Hand Depends on the Side of Stroke in Chronic Stroke Survivors With Mild-to-Moderate Impairment

“…For predominantly right-handed cohorts (as is the case in most studies), contralesional deficits appear to be more severe in those with RHD, in whom the contralesional limb is non-dominant; whereas ipsilesional deficits are more severe in those with LHD. An exception to this observation for those with RHD seems to be in the case when contralesional impairment is most severe (i.e., UEFM < 34) (14). Thus, one might predict that as contralesional impairment worsens, individuals with LHD would have proportionally worse ipsilesional deficits, but individuals with RHD (especially if say UEFM > 34) would not; see Figures 1B,C for two alternative hypotheses.…”

“…Previous work suggests that deficits in the ipsilesional arm and hand varies with the severity of contralesional deficits, especially in the sub-acute and chronic phase after stroke (5)(6)(7)(8). More interestingly, the unilateral motor deficits observed for contralesional and ipsilesional limbs seem to be hemisphere-specific and thus depend on side of stroke lesion (9)(10)(11)(12)(13)(14)(15). For predominantly righthanded cohorts, contralesional deficits appear to be more severe in those with right hemisphere damage (RHD), in whom the contralesional limb is non-dominant.…”

“…Hints of this interaction were implicit in a few previous studies (2,3,14); however, categorical reporting of the Upper Extremity Fugl-Meyer (UEFM) masked this interesting effect. By preserving the continuity of the UEFM and utilizing continuous standardized z-scores, our statistical approach allowed a direct comparison of our regression estimates, thus reflecting effect sizes of each of the candidate predictors.…”

“…In acute stroke survivors, Nowak et al demonstrated that deficits in grip force of the ipsilesional hand were significantly associated with clinical measures of function of the contralesional hand only in LHD (12). Contrary to this, de Paiva Silva et al (14) found that compared to controls and LHD, the ipsilesional hand in chronic stroke survivors was significantly slower and less smooth in RHD especially when contralesional impairment was relatively more severe (UEFM < 34).…”

“…One reason that this prediction remains untested might be methodological in that in these previous studies participants were categorically classified based on the degree of contralesional motor impairment (e.g., mild, moderate, severe) (6,8,14). Categorization (or worse, dichotomization) of a continuous variable presents several concerns, including loss of measurement resolution, an assumption of discontinuity in the underlying construct (in this case motor impairment), unequal subgroup sizes (or biased sampling), and large unexplained residuals in regression models (18)(19)(20).…”