title: Evolution of cortical activation during recovery from corticospinal tract infarction.
abstract: OBJECTIVE
  Recovery from hemiparesis due to corticospinal tract infarction is well documented, but the mechanism of recovery is unknown. Functional MRI (fMRI) provides a means of identifying focal brain activity related to movement of a paretic hand. Although prior studies have suggested that supplementary motor regions in the ipsilesional and contralesional hemisphere play a role in recovery, little is known about the time course of cortical activation in these regions as recovery proceeds.
  
  
  METHODS
  Eight patients with first-ever corticospinal tract lacunes causing hemiparesis had serial fMRIs within the first few days after stroke and at 3 to 6 months. Six healthy subjects were used as controls. Statistically significant voxels during a finger-thumb opposition task were identified with an automated image processing program. An index of ipsilateral versus contralateral activity was used to compare relative contributions of the 2 hemispheres to motor function in the acute and chronic phases after stroke.
  
  
  RESULTS
  Controls showed expected activation in the contralateral sensorimotor cortex (SMC), premotor, and supplementary motor areas. Stroke patients differed from control patients in showing greater activation in the ipsilateral SMC, ipsilateral posterior parietal, and bilateral prefrontal regions. Compared with the nonparetic hand, the ratio of contralateral to ipsilateral SMC activity during movement of the paretic hand increased significantly over time as the paretic hand regained function.
  
  
  CONCLUSIONS
  The evolution of activation in the SMC from early contralesional activity to late ipsilesional activity suggests that a dynamic bihemispheric reorganization of motor networks occurs during recovery from hemiparesis.
authors.affiliation: Columbia-Presbyterian Medical Center, Columbia University, New York, NY, USA. rsm2@columbia.edu
authors.forename: R S
authors.initials: RS
authors.lastname: Marshall
authors.forename: G M
authors.initials: GM
authors.lastname: Perera
authors.forename: R M
authors.initials: RM
authors.lastname: Lazar
authors.forename: J W
authors.initials: JW
authors.lastname: Krakauer
authors.forename: R C
authors.initials: RC
authors.lastname: Constantine
authors.forename: R L
authors.initials: RL
authors.lastname: DeLaPaz
mesh_terms: D000328:Adult; D000368:Aged; D002540:Cerebral Cortex / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality; D006225:Hand / Q000503:physiopathology; D006429:Hemiplegia / Q000503:physiopathology; D006801:Humans; D007238:Infarction / Q000175:diagnosis / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000473:pathology / Q000503:physiopathology; D009068:Movement; D011712:Pyramidal Tracts / Q000098:blood supply* / Q000473:pathology; D012016:Reference Values; D013997:Time Factors