What is the most accurate predictor of poor outcome in patients with anoxic–ischemic encephalopathy?
A: The measurement of somatosensory evoked potentials (SSEPs), especially the N20 response from the primary somatosensory cortex (assessed 20 msec after electrical stimulation of the median nerve at the wrist), has emerged as the most accurate predictor of a poor outcome in patients with anoxic–ischemic encephalopathy. In a meta-analysis, bilateral absence of the N20 response was associated with essentially no false positives (pooled 95% CI, 0 to 2). In some patients, N20 responses are intact at 24 hours after arrest but are lost by 72 hours; once lost, they are not regained, and outcomes are poor.
New England Journal of Medicine - Vol. 361, No. 6, August 6, 2009