Imaging correlates of motor recovery from cerebral infarction and their physiological significance in well-recovered patients

Abstract

We studied motor representation in well-recovered stroke patients. Eighteen right-handed stroke patients and eleven age-matched control subjects underwent functional Magnetic Resonance Imaging (fMRI) while performing unimanual index finger (abduction-adduction) and wrist movements (flexion-extension) using their recovered and non-affected hand. A subset of these patients underwent Transcranial Magnetic Stimulation (TMS) to elicit motor evoked potentials (MEP) in the first dorsal interosseous muscle of both hands. Imaging results suggest that good recovery utilizes both ipsi- and contralesional resources, although results differ for wrist and index finger movements. Wrist movements of the recovered arm resulted in significantly greater activation of the contralateral (lesional) and ipsilateral (contralesional) primary sensorimotor cortex (SM1), while comparing patients to control subjects performing the same task. In contrast, recovered index finger movements recruited a larger motor network, including the contralateral SM1, Supplementary Motor Area (SMA) and cerebellum when patients were compared to control subjects. TMS of the lesional hemisphere but not of the contralesional hemisphere induced MEPs in the recovered hand. TMS parameters also revealed greater transcallosal inhibition, from the contralesional to the lesional hemisphere than in the reverse direction. Disinhibition of the contralesional hemisphere observed in a subgroup of our patients suggests persistent alterations in intracortical and transcallosal (interhemispheric) interactions, despite complete functional recovery.

Figures

Figure 1

Patients showed more activation (p

Figure 2

During the index finger task, patients showed more activation (p

Figure 3

Mean and standard error (SE) of intracortical inhibition (panel a; ICI) and intracortical facilitation (panel b. ICF) in patients. ICI is expressed as the percentage of the degree of inhibition (1- [test/control]) and ICF is expressed as the percentage increase (test/control) in peak-to-peak MEP amplitude.