Background: In clinical practice, magnetic resonance imaging (MRI) is commonly used to assess the severity of a cardiac arrest patient's cerebral injury, utilizing treating neurologists' imaging interpretation. We sought to determine whether clinical interpretation of diffusion-weighted imaging (DWI) helps to determine poor outcome in comatose cardiac arrest patients.
Methods: We analyzed 80 consecutive MRIs from patients in coma following cardiac arrest. Each study was graded as "normal" or "abnormal restricted diffusion" in pre-specified brain regions by two blinded stroke neurologists. Poor outcome was defined as a modified Rankin Scale (mRS) score >4 at 3 months. Formal interpretations of neuroimaging by non-blinded neuroradiologists were compared with the blinded reviews by the stroke neurologists.
Results: DWI abnormalities were highly sensitive (98.5 %) but only modestly specific (46.2 %) for predicting poor neurological outcome. Inter-observer reliability was moderate (kappa = 0.49 ± 0.32), with 91 % agreement between study observers, and no significant differences in study observers' interpretations (p = 0.125). There were, however, significant differences between the study observers and the clinical neuroradiologists in identifying studies showing evidence of global hypoxic-ischemic injury (p = 0.001).
Conclusions: The qualitative evaluation of imaging abnormalities by stroke physicians in comatose cardiac arrest patients is a highly sensitive method of predicting poor outcome, but with limited specificity.