Functional relevance of abnormal fMRI activation pattern after unilateral schizencephaly.

Brain plasticity was investigated in a child with a hemiplegia due to unilateral schizencephaly involving the sensorimotor cortex. This focal lesion led to a dramatic functional reorganization of the undamaged hemisphere, as evidenced by the unusual pattern of fMRI activation during paretic finger movements. The functional relevance of the activation in the undamaged motor cortex was supported by the finding that TMS of this area yielded a response in the paretic hand, indicating that it controls both hands. However, this reorganization was not restricted to the primary motor cortex, but also concerned other structures involved in the control of movements, as shown by the activation of contralesional SMA and thalamus. In contrast, the fMRI activation in the damaged sensorimotor cortex during paretic hand movements appears functionally irrelevant.