Degree of neurological recovery as a function of initial neuron-specific enolase levels and electroencephalographic patterns in survivors of cardiac arrest: a bicentric study.

Abstract

The relationship between early markers of brain injury (biomarkers and EEG patterns) and the subsequent degree of neurological recovery in cardiac arrest survivors at 3 months has received little attention. We aimed to examine this relationship and describe patients who survived despite having initial unfavorable NSE levels and EEG patterns. Cohort study analysing two prospective registries (CHUV Lausanne, Switzerland; Cochin Hospital, France). We included comatose patients after cardiac arrest who had at least one serum NSE at 48 h and an EEG ≥ 24 h. NSE was classified as < 17 µg/L, 17 ≤ NSE < 41 µg/L, 41 ≤ NSE ≤ 60 µg/L or > 60 µg/L. EEG was classified as highly malignant, malignant or benign. The primary outcome was the level of neurological recovery at 3 months according to the Cerebral Performance Category (CPC) scale. NSE and EEG were compared between the CPC groups. We also assessed the number of patients with a CPC 1 or 2 and either an NSE > 60  µg/L or a highly malignant EEG. Between 2017 and 2024, 966 comatose patients were included. The NSE level ranges at 48 h differed significantly across the CPC groups, higher values being associated with poorer functional outcomes; this significant difference was also notable in survivors (CPC1 vs CPC2 vs CPC3) (p < 0.001). EEG patterns were also significantly different across CPC groups: the more severe the EEG pattern, the worse the functional outcome (p < 0.001). Regarding false-positive prediction of unfavorable outcome, NSE > 60 µg/L was found in 2/176 patients (1.2 %) who reached CPC 1 (maximum at 79.5 µg/L) and 3/138 patients (2.2 %) who reached CPC 2 at follow up (maximum at 68 µg/L); none of them had other markers of unfavorable outcome. No patients with CPC 1 or 2 had a highly malignant EEG. This large bicentric study found a progressive worsening of neurological outcomes at 3 months with higher NSE levels or deteriorating EEG patterns. Thus, both NSE and EEG may be valuable for predicting cognitive impairments in survivors. Only a few patients with favorable outcome had NSE levels > 60 µg/L, and none of them had other markers of unfavorable outcome.