Radiological signs of hypoxic-ischaemic encephalopathy on head computed tomography for prediction of poor functional outcome after cardiac arrest - a prospective observational cohort study

INTRODUCTION: Qualitative assessment of hypoxic ischaemic encephalopathy on computed tomography (CT) after cardiac arrest is limited by interrater agreement. We explored how qualitative assessment can be improved.

METHODS: In-depth analysis of radiological items evaluated in a prospective sub-study within the Targeted Hypothermia versus Targeted Normothermia after out-of-hospital cardiac arrest (TTM2) trial examining unconscious patients with CT > 48 h ≤ 7 days. Prognostic performance to diagnose poor outcome (modified Rankin Scale 4-6 at six months) and interrater agreement were evaluated for: "loss of grey-white matter distinction" and "sulcal effacement" at different anatomical levels, "the Pseudo Subarachnoid Haemorrhage Sign", "the White Cerebellum Sign", and "the Reversal Sign".

RESULTS: We included 140 patients examined with CT at median 84 h (IQR 66-109) post-arrest. Median age was 68 years (IQR 59-76), 106 (76%) were male and 105 (75%) had a poor functional outcome. "Loss of grey-white matter distinction" predicted poor functional outcome with 100% specificity and 45-50% sensitivity. The specificity for "sulcal effacement" was 93-99% and the sensitivity 29-49%. "The Pseudo Subarachnoid Haemorrhage Sign", "the Reversal Sign", and the "White Cerebellum Sign" predicted poor functional outcome with 99-100% specificity and 8-11% sensitivity. The highest interrater agreement was "moderate" (κ = 0.74) for the loss of grey-white matter distinction at high convexity level.

CONCLUSION: Extensive and bilateral loss of grey-white matter distinction on CT is associated with poor functional outcome after cardiac arrest and yielded the highest interrater agreement. Signs of sulcal effacement were less reliable and should thus be used with caution in neuroprognostication. The TTM2 CT substudy is registered at clinicaltrials.gov (NCT03913065).