Bilateral Reappearance of the N20 Potential in a Normothermic Young Woman Post-Anoxic Brain Injury

Hypoxic-ischemic brain injury is a well-known consequence of cardiac arrest and providing an accurate prognostication remains a challenge, especially in decisions related to withdrawal of care. Bilateral absence of the cortical response (N20 potential) on median somatosensory evoked potentials, on days 1 to 3 after the return of spontaneous circulation, is widely considered as the most reliable predictor of poor outcome with a high specificity and a low false-positive rate. The authors describe the case of a young comatose woman after hypoxic injury because of cardiac arrest whose initial median somatosensory evoked potentials revealed bilateral absence of the N20 response associated with evidence of selective injury to both perirolandic cortices and basal ganglia on brain MRI. This patient made a substantial recovery associated with bilateral reappearance of the N20 potential and resolution of the neuroimaging abnormalities.This case revealed that an acute selective and reversible hypoxic injury to both perirolandic cortices may lead to a temporary loss of the N20 responses and an inaccurate prediction of poor outcome after cardiac arrest. It emphasizes on the importance of adopting a multimodal approach in the prognostic assessment of survivors of cardiac arrest.