Reorganization of the primary somatosensory cortex during stroke recovery

ObjectiveAnimal and human studies have indicated that stroke induces reorganization of the motor and somatosensory cortices. We aimed to clarify how changes in the primary somatosensory (SI) cortex correlate with stroke recovery.MethodsWe recorded somatosensory evoked fields (SEFs) with magnetoencephalography from 15 patients with stroke affecting upper extremity motor function. The size of the hand representation in the SI cortex was calculated from the Euclidean distance between the sources of SEFs to thumb and little finger tactile stimulation. The measurements were made at 1–7 days (T0), at 1 (T1), and at 3 months (T2) after stroke, with concomitant evaluation of hand function.ResultsThe affected hand function was improved at T1 and T2 compared with T0 (p < 0.01). At T1, the SI hand representation in the affected hemisphere was enlarged compared with T0 or T2 (12.6 ± 0.8 at T1vs. 9.6 ± 0.8 mm at T0 and 10.2 ± 0.8 at T2, p < 0.05). In patients with subcortical infarction, the increase in cortical representation at T1 correlated strongly with impairment of hand function (r = 0.8, p < 0.01).ConclusionReorganization of the SI cortex provokes a transient enlargement of the hand representation that normalizes as hand functions are regained.SignificanceThe temporal evolution of plastic changes during stroke recovery might be useful in evaluating motor recovery.