Modulation of the BOLD-response in early recovery from sensorimotor stroke

Background: The BOLD signal in functional MRI ( fMRI) is closely related to neural activity. Objective: To investigate if this relationship is disrupted after ischemic stroke. Methods: BOLD activity during tactile exploration of objects was measured with fMRI at 1 week ( subacute), 2 to 4 weeks ( early chronic), and after 1 month ( chronic) after the first completed brain infarction affecting the sensorimotor cortex in eight patients. Functional integrity of the motor cortical output system was assessed with transcranial magnetic stimulation (TMS). Results: Early after infarction the BOLD-response occurred in the adjacent cortical vicinity related to finger movements of the affected hand. However, during the early chronic stage there was a transient lack of this activation despite clinical improvement of hand function and preserved motor evoked potentials. The BOLD activity reappeared after further improvement in the chronic stage. Conclusions: Our findings suggest a transient hemodynamic-electrical decoupling in the post-ischemic cerebral cortex during the early phase of spontaneous clinical recovery.