Increased fMRI activation in the primary sensorimotor cortex (M1S1) after constraint induced movement therapy in congenital hemiparesis

Objectives: Constraint Induced Movement Therapy (CIMT) is an effective approach to improve the paretic hand function in children with congenital hemiparesis. The scope of our study was to assess the neurobiological basis for the functional improvement after CIMT by functional MRI (fMRI). Methods: Eleven patients (age: 10–30 years; median: 12 years; 6 females) with congenital hemiparesis due to a pre-, peri- or neonatally acquired, unilateral cortico-subcortical infarction in the middle cerebral artery territory and preserved crossed cortico-spinal projections to the paretic hand (as determined by transcranial magnetic stimulation) were included. After a twelve-day CIMT training period in an inpatient setting, all patients showed a significant improvement of the motor function of the paretic hand (Wolf Motor Function Test). FMRI during repetitive active and passive movements of the paretic and the non-paretic hand was performed immediately (<48h) before and after CIMT. Results: After CIMT, 8/11 patients showed increased fMRI activation during paretic hand movement. Of these, four patients with potential confounding factors (e.g., higher squeezing pressures after CIMT) were not included in further analysis. In four patients with a valid increase in fMRI activation, the increase was located in the contralateral M1S1 (4/4), the supplementary motor area (2/4), the cerebellum (1/4), the ipsilateral M1S1 (1/4) and the ipsilateral premotor cortex (1/4). In two of these, a follow-up fMRI three months after CIMT could be performed. FMRI showed a decrease in activation to the base level before CIMT, whereas the improved motor function of the paretic hand was preserved. Conclusion: Neuromodulative effects of CIMT were detected consistently in the primary sensorimotor cortex of the affected hemisphere, contralateral to the paretic hand. These observations indicate that the potential for neuromodulation is preserved in the lesioned hemisphere even after the early disruption of neural circuits.