ROLE OF DIFFUSION-WEIGHTED IMAGING (DWI) IN EARLY DETECTION OF ISCHEMIC STROKE

Abstract

Background: Acute ischemic stroke is a leading cause of death and disability worldwide, and early accurate imaging is critical for timely reperfusion therapy. Diffusion-weighted imaging (DWI) has emerged as a highly sensitive modality for detecting acute cerebral ischemia, but locally relevant evidence from Pakistan remains limited.

Objective: To evaluate the diagnostic efficacy of DWI in the early detection of acute ischemic stroke and to assess the relationship between DWI findings, stroke severity, and short-term functional outcome.

Methods: An observational cross-sectional study was conducted at Lady Reading Hospital, Peshawar, over a four-month period. Thirty-eight adults (18–80 years) presenting with suspected acute ischemic stroke within 24 hours of symptom onset were enrolled. All participants underwent MRI including T1-weighted, T2-weighted, and DWI sequences with ADC mapping within 24 hours of symptom onset. Final diagnosis at discharge served as the reference standard. Diagnostic accuracy of DWI was calculated, and correlations between DWI lesion size, admission NIH Stroke Scale (NIHSS) scores, and discharge modified Rankin Scale (mRS) scores were analyzed.

Results: Of 38 participants, 33 (86.8%) were classified as having acute ischemic stroke. DWI identified acute ischemic lesions in 30 of 33 stroke patients, yielding a sensitivity of 90.9%, specificity of 80.0%, positive predictive value of 96.8%, negative predictive value of 57.1%, and overall accuracy of 89.5%. DWI detected significantly more acute lesions than T1-weighted (48.5%) and T2-weighted (60.6%) imaging (p < 0.01). DWI lesion size showed a strong positive correlation with admission NIHSS scores (r = 0.64, p = 0.001) and a moderate correlation with discharge mRS scores (r = 0.47, p = 0.009). Three clinically confirmed strokes (9.1%) were DWI-negative; these cases occurred predominantly among patients with lower NIHSS scores, earlier time-to-MRI, and posterior circulation involvement.

Conclusion: DWI is a highly accurate imaging modality for the early detection of acute ischemic stroke and demonstrates superior performance compared with conventional MRI sequences. DWI lesion burden correlates with neurological severity and early functional outcome, supporting its prognostic value. However, DWI may be negative in a minority of clinically confirmed strokes, particularly in minor and posterior circulation presentations, underscoring the need for clinical correlation and, when indicated, repeat or supplementary imaging.