Normal brain activation in hemiatrophy due to multiple sclerosis: a functional MRI case study

Evidence from recent functional magnetic resonance imaging studies suggests that adaptive cortical changes ('plasticity') could participate in the maintenance of function in multiple sclerosis (MS). Here, we addressed the impact of brain atrophy on the pattern of cerebral activation in an MS patient with a relapsing-remitting course. This patient showed mildly disabling hemiparesis of the left side (EDSS 2.0), and corresponding brain hemiatrophy (15% volume reduction) of the right hemisphere. The clinical syndrome was considered to result from a lesion in the corona radiata involving corticospinal fibers. Motor-evoked potential recordings confirmed substantial axonal damage to the pyramidal tract arising from that hemisphere. Irrespective of these asymmetries, normal brain activation was found for hand and foot movements for both brain sides. This demonstrates that brain atrophy itself does not necessarily induce cortical adaptive changes, even if mild disability is present. On the other hand, significantly disabling distinct clinical syndromes e.g. arising from spinal cord lesions may evoke cortical changes irrespective of brain atrophy. This issue has to be studied in longitudinal investigations.