Motor Deficits in the Ipsilesional Arm of Severely Paretic Stroke Survivors Correlate With Functional Independence in Left, but Not Right Hemisphere Damage

Abstract

Chronic stroke survivors with severe contralesional arm paresis face numerous challenges to performing activities of daily living, which largely rely on the use of the less-affected ipsilesional arm. While use of the ipsilesional arm is often encouraged as a compensatory strategy in rehabilitation, substantial evidence indicates that motor control deficits in this arm can be functionally limiting, suggesting a role for remediation of this arm. Previous research has indicated that the nature of ipsilesional motor control deficits vary with hemisphere of damage and with the severity of contralesional paresis. Thus, in order to design rehabilitation that accounts for these deficits in promoting function, it is critical to understand the relative contributions of both ipsilesional and contralesional arm motor deficits to functional independence in stroke survivors with severe contralesional paresis. We now examine motor deficits in each arm of severely paretic chronic stroke survivors with unilateral damage (10 left-, 10 right-hemisphere damaged individuals) to determine whether hemisphere-dependent deficits are correlated with functional independence. Clinical evaluation of contralesional, paretic arm impairment was conducted with the upper extremity portion of the Fugl-Meyer assessment (UEFM). Ipsilesional arm motor performance was evaluated using the Jebsen-Taylor Hand Function Test (JTHFT), grip strength, and ipsilesional high-resolution kinematic analysis during a visually targeted reaching task. Functional independence was measured with the Barthel Index. Functional independence was better correlated with ipsilesional than contralesional arm motor performance in the left hemisphere damage group [JTHFT: [r ₍₁₀₎ = -0.73, p = 0.017]; grip strength: [r ₍₁₀₎ = 0.64, p = 0.047]], and by contralesional arm impairment in the right hemisphere damage group [UEFM: [r ₍₁₀₎ = 0.66, p = 0.040]]. Ipsilesional arm kinematics were correlated with functional independence in the left hemisphere damage group only. Examination of hemisphere-dependent motor correlates of functional independence showed that ipsilesional arm deficits were important in determining functional outcomes in individuals with left hemisphere damage only, suggesting that functional independence in right hemisphere damaged participants was affected by other factors.

Keywords: CVA; functional outcome; kinematics; motor deficits; upper extremity.

Figure 1

Experimental setup for the kinematic task. (A) An illustration of the KineReach setup. Participants are seated in front of a table with the chin resting on a mirrored surface that displayed the task and occluded view of the hands. Sensors were placed on the ipsilesional hand and upper arm. The hand was supported on an air sled. (B) Schematic of the ipsilesional arm reaching task showing movement of a cursor to the middle target. Participants were asked to move the cursor (representing the position of the hand) quickly into a target that appeared in one of three directions in a pseudorandom manner. The task consisted of 99 trials.

Figure 2

Functional independence is correlated with clinical measures of performance in the ipsilesional and contralesional arms. Functional independence is better correlated with ipsilesional arm clinical measures of performance in the LHD group (n = 10), and by contralesional arm impairment in the RHD group (n = 10). **represents statistically significant correlations; ^~represents correlations that are not statistically significant.

Figure 3

Ipsilesional arm reaching task. (A) Location of the hand at peak velocity and at the end of movement for each trial in a representative left- (LHD) and right- (RHD) hemisphere damaged individual. Ellipses represent the 99% confidence interval of the data from each target for each individual. (B) Mean ratio of variable error at end of movement relative to that at peak velocity for each target in a group. RHD produces a statistically significantly higher ratio of variable error than LHD. Error bars represent 1 s.e.m. across participants in each group (10 LHD, 10 RHD).

Figure 4

Functional independence and ipsilesional arm motor performance are correlated with kinematic measures of performance in the ipsilesional arm. Functional independence and motor performance in the LHD group (n = 10) are better correlated with an ipsilesional arm optimal trajectory control vs. impedance control measure of hand kinematic performance. The RHD group (n = 10) does not have a statistically significant linear relation between any of the kinematic measures and functional independence/ipsilesional motor performance. **represents statistically significant correlations; ^~represents correlations that are not statistically significant.