Reversed discrepancy between CT and diffusion-weighted MR imaging in acute ischemic stroke.

Area of Science:

• Neuroradiology
• Cerebrovascular Diseases
• Medical Imaging

Background:

• Acute cerebral ischemia diagnosis relies on timely imaging.
• Computed tomography (CT) and diffusion-weighted imaging (DWI) are crucial for detecting early ischemic changes.
• Discrepancies between CT and DWI can impact treatment decisions.

Purpose of the Study:

• To investigate the detectability of early CT ischemic lesions on DWI.
• To define and characterize 'reversed discrepancy' (RD) in acute middle cerebral artery (MCA) infarction.
• To assess the clinical significance of RD lesions.

Main Methods:

• Retrospective analysis of CT and MR images from 70 acute MCA infarction patients within 6 hours of symptom onset.
• Identification of reversed discrepancy (RD): parenchymal hypoattenuation on CT without hyperintensity on DWI.
• Quantitative analysis of CT Hounsfield units (HU), apparent diffusion coefficients (ADCs), and perfusion parameters for RD lesions.

Main Results:

• Reversed discrepancy (RD) was identified in 12.9% of patients, predominantly in the basal ganglia (89%).
• RD lesions showed lower mean HU on CT and no significant decrease in ADC or cerebral blood flow.
• Delayed DWI detected hyperintensity in 88.8% of RD lesions, all progressing to infarction; CT underestimated lesion extent compared to DWI in 66% of RD cases.

Conclusions:

• Early CT hypoattenuation indicating ischemia may be missed by DWI, particularly in the basal ganglia.
• Reversed discrepancy (RD) lesions, though uncommon, invariably progress to infarction.
• DWI may underestimate the true extent of severe ischemic tissue in acute MCA infarction.