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

E Y Kim1, J W Ryoo, H G Roh

  • 1Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.

AJNR. American Journal of Neuroradiology
|October 13, 2006
PubMed
Abstract

Insights

Early CT scans may miss some acute ischemic lesions, especially in the basal ganglia. These lesions, termed reversed discrepancy, often progress to infarction and may be underestimated by diffusion-weighted imaging (DWI).

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.

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