Postmortem histopathology of electroencephalography and evoked potentials in postanoxic coma

Early EEG patterns and SSEP responses are associated with neurological recovery of comatose patients with postanoxic encephalopathy after cardiac arrest. However, the nature and distribution of brain damage underlying the characteristic EEG and SSEP patterns are unknown. We relate EEG and SSEP findings with results from histological analyses of the brains of eleven non-survivors. With restoration towards continuous rhythms within 24 h after cardiac arrest, no signs of structural neuronal damage were observed. Absent SSEP responses were always accompanied by thalamic damage. Pathological burst suppression patterns were associated with a variable degree of neuronal damage to cortex, cerebellum and hippocampus. In patients with additional thalamic involvement, burst-suppression with identical bursts was observed, a characteristic EEG pattern presumably reflecting residual activity from a relatively isolated and severely compromised cortex.