Regional distribution of anoxic brain injury after cardiac arrest: clinical and electrographic correlates

IntroductionDisorders of consciousness, EEG background suppression and epileptic seizures are associated with poor outcome after cardiac arrest. The underlying patterns of anoxic brain injury associated with each remain unknown. Our objective was to identify the distribution of anoxic brain injury after cardiac arrest, as measured with diffusion MRI, and to define the regional correlates of disorders of consciousness, EEG background suppression, and seizures. MethodsWe analyzed patients from a prospectively-maintained, single-center database of unresponsive patients who underwent diffusion-weighted MRI following cardiac arrest (n = 204). We classified each patient based on recovery of consciousness (command-following) before discharge, the most continuous EEG background (burst suppression versus continuous), and the presence or absence of seizures. Anoxic brain injury was measured using the apparent diffusion coefficient (ADC) signal. We identified abnormalities in ADC relative to control subjects without cardiac arrest (n = 48) and used voxel lesion symptom mapping to identify regional associations with disorders of consciousness, EEG background suppression, and seizures. We then used a bootstrapped lasso regression procedure to identify robust, multivariate regional associations with each clinical and EEG variable. Finally, using area under receiver operating characteristic curves, we then compared the classification ability of the strongest regional associations to that of brain-wide summary measures. ResultsCompared to control subjects, cardiac arrest patients demonstrated a reduction in the ADC signal that was most significant in the occipital lobes. Disorders of consciousness were associated with reduced ADC most prominently in the occipital lobes, but also in the basal ganglia, medial thalamus and cerebellar nuclei. Regional injury more accurately classified patients with disorders of consciousness than whole-brain injury. Background suppression mapped to a similar set of brain regions, but regional injury could no better classify patients than whole-brain measures. Seizures were less common in patients with more severe anoxic injury, particularly in those with injury to the lateral temporal white matter. DiscussionAnoxic brain injury was most prevalent in posterior cerebral regions, and this regional pattern of injury was a better predictor of disorders of consciousness than whole-brain injury measures. EEG background suppression lacked a specific regional association, but patients with injury to the temporal lobe were less likely to have seizures. Collectively, our results suggest that the regional pattern of anoxic brain injury is relevant to the clinical and electrographic sequelae of cardiac arrest and may hold importance for prognosis.