Changes in hemodynamic responses during movements of the upper extremities in the acute phase after stroke: A fNIRS study

Abstract

The acute phase of stroke is accompanied by functional changes and interplay of both hemispheres. However little is known on how the time course of functional motor recovery is related to the progression of symmetry in the motor areas of the brain. This study aimed to assess the time course of both hemodynamic patterns of cortical motor areas using functional near infrared spectroscopy (fNIRS) and functional recovery during the first months after stroke. Unaffected upper limb movements-related contralateral motor areas activity showed no significant changes. Eight right-handed first ischemic/hemorrhagic stroke patients (60 ± 8 yrs, 3 female and 5 men) with mild to severe hemiparesis were examined with fNIRS measurements and functional motor recovery (Fugl-Meyer score) tests every two weeks during two months (five sessions). We investigated hemodynamic changes over the contralateral and ipsilateral motor areas with a 2 × 8-channel fNIRS system (Oxymon MkIII ® ) during a unilateral intermittent isometric forearm task (1 Hz) at self-selected submaximal force levels. Laterality index (LI) was computed to evaluate the asymmetry of hemodynamic changes from the two hemispheres. Affected upper limb movements were associated early with a bilateral cortical activity before shifting to contralateral patterns ( P < 0.01). Progressive lateralization was observed with LI increases over the first 4 sessions (from −0.24 ± 0.18 to 0.36 ± 0.27, P < 0.05) prior to level off (session 5, 0.25 ± 0.39), as did the Fugl-Meyer score. These findings suggest that cortical reorganization monitoring with fNIRS during the first weeks after stroke should be considered further when assessing functional motor recovery in stroke rehabilitation services.