Functional reorganization of sensorimotor cortex in chronic hemispheric ischemic stroke patients with different severity of motor deficit

Abstract

Motor recovery after ischemic stroke is associated with the neuralnetworks reorganization. fMRI studies of these networks inpatients with mild motor deficit showed that activation patterncan be used for the prognosis of functional recovery. However,characteristics and clinical relevance of activation patterns inpatients with severe to moderate motor deficit, its effective functioningin patients with different severity of primary sensorimotorsystem components (corticospinal tract [CST] and primarysensorimotor [SM] cortex) injury were not investigated. Twentyfivechronic hemispheric ischemic stroke patients were studied(13 males, 12 females; median age 38.05.9 years). Dependingon the severity of hand motor impairment and functional outcomethe patients were divided into 3 groups. All patients underwent1.5 T fMRI (Siemens Avanto) with passive block paradigmof paretic index finger movement (1 Hz frequency). Statisticmaps of group activation showed significant differences ingroups with different functional outcome: the more severe wasmotor deficit, the less SM activation volume size in injuredhemisphere was seen, and activation cluster center movedtowards non-primary motor cortex. The association between theactivation volume of SM and structural integrity of CST, assessedby fractional anisotropy index was revealed. Statistic maps ofindividual activation showed SM activation in injured hemispherein 38% patients with unfavourable (severe paresis, plegia)and moderate recovery with different physiologic lateralization,that is typical for the group with good recovery (mild and moderateparesis). These data do not allow us to consider the activationpattern as a marker of motor recovery and prognostic factorin patients with severe and moderate motor deficit. Our resultsshowed that sensorimotor networks formation and functioningdiffer depending on the CST sparing, and its effective work ispossible in certain degree CST integrity.

Keywords

• ischemic stroke
• motor recovery
• fmri
• sensorimotor cortex activation pattern
• fractional anisotropy