Spectacular shrinking deficit: insights from multimodal magnetic resonance imaging after embolic middle cerebral artery occlusion in Sprague-Dawley rats.

Almost no data is available on the serial changes in the brain after spectacular shrinking deficit (SSD) that may help understand this relatively rare clinical phenomenon. Quantitative diffusion-(DWI), perfusion-(PWI), T(1)-(T1WI), T(2)-weighted (T2WI), and functional magnetic resonance imaging (fMRI) were performed before, during, and up to 7 days after embolic middle cerebral artery occlusion (eMCAO) in male Sprague-Dawley rats (n=9). Region of interest (ROI) analysis was used to evaluate structural and functional MR signal changes within three ROIs defined by the apparent diffusion coefficient (ADC), cerebral blood flow (CBF) signatures, and final tissue viability. DWI, PWI, and T2WI lesion volumes were calculated using previously established viability thresholds and final infarct volumes ascertained with 2,3,5-triphenyltetrazolium chloride (TTC) staining. Serial MRI demonstrated spontaneous reperfusion of initially hypoperfused MCA regions accompanied by substantial reduction of initial ADC and CBF lesions and gradual recovery of neurological outcome. Recovery rates of CBF/ADC abnormalities differed among ROIs. Functional magnetic resonance imaging showed persistent tissue dysfunction after the recovery of the CBF/ADC lesions. This study may facilitate our understanding of the pathophysiological mechanisms by which early, spontaneous reperfusion affects tissue fate and neurological function.