Infarct hemisphere and noninfarcted brain volumes affect locomotor performance following stroke

Abstract

Objective: Brain damage within the right middle cerebral artery (MCA) territory is particularly disruptive to mediolateral postural stabilization. The objective of this cross-sectional study was to test the hypothesis that chronic right MCA infarcts (as compared to left) are associated with slower and more bilaterally asymmetrical gait. We further hypothesized that in those with chronic right MCA infarct, locomotor performance is more dependent on gray matter (GM) volumes within noninfarcted regions of the brain that are involved in motor control yet lie outside of the MCA territory.

Methods: Gait speed was assessed in 19 subjects with right MCA infarct, 20 with left MCA infarct, and 108 controls. Bilateral plantar pressure and temporal symmetry ratios were calculated in a subset of the cohort. GM volumes within 5 regions outside of the MCA territory (superior parietal lobe, precuneus, caudate, putamen, and cerebellum) were quantified from anatomic MRIs.

Results: Right and left infarct groups had similar poststroke duration (7.6 ± 6.0 years), infarct size, and functional independence. The right infarct group demonstrated slower gait speed and greater asymmetry compared to the left infarct group and controls (p < 0.05). In the right infarct group only, those with larger GM volumes within the cerebellum (r(2) = 0.32, p = 0.02) and caudate (r(2) = 0.56, p < 0.001) exhibited faster gait speed.

Conclusion: Individuals with chronic lesions within the right MCA territory, as compared to the left MCA territory, exhibit slower, more asymmetrical gait. For these individuals, larger GM volumes within regions outside of the infarcted vascular territory may help preserve locomotor control.

Figure 1. Effects of middle cerebral artery infarct on plantar pressure symmetry when walking

Plantar pressures of a representative control (A) and subjects with left (B) and right (C) middle cerebral artery (MCA) infarct. Values within each sensor region reflect the average maximum pressure (kPa) achieved over 50 consecutive steps. In the control group and left MCA infarct group, the average maximum pressure experienced during the stance phase of walking was bilaterally symmetrical. In those with right MCA infarct, however, the average maximum pressure experienced by the affected lower limb was lower than that of the unaffected lower limb.

Figure 2. Relationships between gait speed and gray matter tissue volume within the caudate and cerebellum

Within the right middle cerebral artery (MCA) infarct group, subjects with larger gray matter volumes within the caudate (A) or cerebellum (B) had faster preferred walking speeds. This relationship was independent of age, sex, and body mass index. In controls and those with left MCA infarct, gait speed did not correlate with gray matter volume within either region.