Abstract
Background: While primary motor cortex (M1) has been demonstrated to be crucial for motor recovery in a recent meta-analysis including fMRI and TMS studies, other functional neuroimaging studies have found that activity in a broader sensorimotor cortical network correlate with motor recovery. The heterogeneity of stroke lesions and the small sample size characterizing many studies could account for these discrepancies. Hypothesis : The strength of task-related activity in primary motor cortex predicts motor recovery in a clinically homogenous population of acute lacunar stroke patients. Methods: We used fMRI to investigate the neural mechanisms of stroke recovery. We studied 18 stroke patient (4 females, 14 males) after their first single lacunar stroke (7 right , 11 left hemisphere). The lesions caused pure hemiparesia one week after stroke onset (mean 7.2 days; range 2 -15). Lesions were limited to the deep territory of the anterior choroid artery, involving the corticospinal tract at the level of the internal capsule or the corona radiata ( Figure 1 ). Patients were matched to 18 healthy controls for age and sex. Motor impairment was assessed using the NIH Stroke Scale (NIHSS), the Fugl-Meyer Scale (FMS), Finger Tapping Score (FTS), Purdue Pegboard and simple reaction times 7 days and 6 months after stroke. At 6 months, a global motor recovery score was computed using the FMS and the FTS to assess motor recovery. Functional MRI scans were obtained using a self-paced finger tapping (FT) task implemented as a block design alternating right FT, left FT and rest. Data were processed using SPM8. In the first level analysis “FT minus fixation” contrasts were computed for the impaired hand. At the second level, multiple regression was used to assess the effect of the motor recovery score on the FT-related motor activity (threshold p<0.05 FWE; extent threshold k=5). Age and FT rate recorded during the experiment were included as covariates in the second level model. Results: As a group, the patients showed good recovery at 6 months. Both patients and controls exhibited a typical pattern of FT task-related activity. Activity in primary motor cortex predicted motor recovery at 6 months, after adjustment for age and FT rate. MNI coordinates = [-34,-14,48] See Figure 1 . Conclusions: Primary motor cortex activity, measured soon after stroke onset, predicts motor recovery assessed at 6 months post-stroke. fMRI measurements made in the early phase of stroke recovery could be useful to derive prognostic biomarkers in both clinical practice and clinical trials investigating novel treatments, such as stem cell administration.
Published Version
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