Efficacies of Somatosensory Evoked Potential and Diffusion-Weighted Magnetic Resonance Imaging as Predictors of Prognosis for Patients Experiencing Coma after Cardiac Arrest

Chae, Sang Hee; Kim, Soo Hyun; Choi, Se Min; Choi, Seung Pill; Park, Kyu Nam

Abstract

BACKGROUND
The aim of this study was to examine the efficacies of somatosensory evoked potential (SEP) and diffusion-weighted magnetic resonance imaging (DWI) in predicting the clinical prognosis of comatose patients following cardiac arrest.
METHODS
Forty-one patients resuscitated from out-of hospital cardiac arrest (OHCA) were retrospectively studied. After return of spontaneous circulation (ROSC), SEP was conducted between one and three days after resuscitation, and DWI was conducted within five days of resuscitation. SEP was classified into three grades: normal, delayed conduction or unilateral loss of the N20 peak, and bilateral loss of the N20 peak. Bilateral loss of the N20 peak was considered a predictor of poor prognosis. For DWI, diffuse signal intensity (SI) abnormality in the cerebral cortex or abnormality in other brain areas in addition to the bilateral cerebral cortex was taken as a predictor of poor prognosis. For patient clinical prognosis, the Glasgow-Pittsburgh Cerebral Performance Category (CPC) was used to evaluate neurological results at the time of discharge. Resulting CPC scores of 1 and 2 were considered as a favorable prognosis, and scores of 3, 4, and 5 were considered as a poor prognosis. Sensitivity, specificity, positive predictive value, and negative predictive value for the prediction of poor prognosis were analyzed for each test individually and for the combination of the two tests.
RESULTS
Among the 41 subject patients, 31 underwent SEP, 30 underwent DWI, and 20 underwent both tests. The prognosis predictor of SEP (bilateral loss of the N20 peak) predicted poor prognosis with 56.5% sensitivity, 100% specificity, 100% positive predictive value, and 44.4% negative predictive value. The prognosis predictor of DWI (diffuse SI abnormality in the cerebral cortex or abnormality in other brain areas in addition to the bilateral cerebral cortex) predicted poor prognosis with 85% sensitivity, 100% specificity, 100% predictive value, and 76.9% predictive value. For patients who underwent both tests, the sensitivity and negative predictive value for the prediction of poor prognosis increased to 92.3% and 87.5%, respectively, and the specificity and positive predictive value were maintained at 100%.
CONCLUSIONS
The accuracy of poor prognosis prediction for patients in prolonged comas after resuscitation is enhanced by combining the results of SEP and DWI along with the individual results of each test.