The density ratio of grey to white matter on computed tomography as an early predictor of vegetative state or death after cardiac arrest

Objectives: To evaluate whether the ratio (in Hounsfield units; HU) of grey matter (GM) to white matter (WM) on computed tomography (CT) scans taken within 24 h of resuscitation can be used as a predictor of outcome. Methods: 28 patients who resuscitated from cardiac arrest and had head CT performed within 24 h of resuscitation were retrospectively investigated. 27 subjects with normal head CT findings served as controls. Comatose patients were divided into two groups: those with a Glasgow outcome scale (GOS) score of 3 -5 (good outcome subgroup) and those with a GOS score of 1 -2 (poor outcome subgroup). HU were measured in GM and WM at the level of the basal ganglia on non-contrast CT scans. Results: The density ratio of GM to WM was significantly lower in comatose patients than in controls (mean 1.21 vs 1.32, p < 0.001). The GM: WM ratio was significantly lower in the poor subgroup than in the good subgroup (mean 1.19 vs 1.28, p < 0.001). Receiver operating characteristic curve analysis determined a cutoff value of a GM: WM ratio of less than 1.22 for vegetative state or death. This value predicted vegetative state or death with a sensitivity of 63%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 56%. Conclusion: The GM/ WM ratio correlates with the outcome of hypoxic ischaemic encephalopathy and may be useful as an objective early predictor of vegetative state or death in comatose patients after cardiac arrest.