Negative fluid-attenuated inversion recovery imaging identifies acute ischemic stroke at 3 hours or less

Area of Science:

• Neuroradiology
• Neuroimaging
• Stroke Imaging

Background:

• Accurate timing of ischemic stroke is crucial for treatment decisions.
• Diffusion-weighted imaging (DWI) is sensitive to acute ischemic lesions.
• Fluid-attenuated inversion recovery (FLAIR) imaging's role in early stroke detection requires further evaluation.

Purpose of the Study:

• To assess the utility of FLAIR imaging as a surrogate marker for determining the age of ischemic stroke lesions within the initial 6 hours.
• To compare the sensitivity and specificity of FLAIR and DWI in detecting acute ischemic lesions.

Main Methods:

• Analysis of FLAIR and DWI sequences from 120 ischemic stroke patients within 6 hours of symptom onset.
• Evaluation of acute ischemic lesion visibility on FLAIR, both alone and with knowledge of DWI, compared to DWI.
• Statistical analysis including specificity, positive predictive value, sensitivity, negative predictive value, and multivariate regression.

Main Results:

• A "mismatch" of positive DWI and negative FLAIR highly suggested lesions within 3 hours (specificity 0.93, PPV 0.94).
• Lesion visibility was lower on FLAIR (35.6% alone, 62.5% with DWI knowledge) compared to DWI (97.1%).
• FLAIR sensitivity for acute lesions increased from 27.0%/50.0% (≤3 hours) to 56.7%/93.3% (3-6 hours) (FLAIR alone/with DWI knowledge).

Conclusions:

• The combination of positive DWI and negative FLAIR effectively identifies patients likely within the 3-hour time window.
• FLAIR imaging's sensitivity for acute ischemic lesions improves over time, approaching 100% between 3 and 6 hours post-symptom onset.