Reorganization of the primary somatosensory cortex during stroke recovery

OBJECTIVE Animal 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. METHODS We 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. RESULTS The 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 T₁ vs. 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). CONCLUSION Reorganization of the SI cortex provokes a transient enlargement of the hand representation that normalizes as hand functions are regained. SIGNIFICANCE The temporal evolution of plastic changes during stroke recovery might be useful in evaluating motor recovery.