Generalized epileptiform discharges in postanoxic encephalopathy: Quantitative characterization in relation to outcome

Abstract

Summary Objective Electrographic status epilepticus is observed in 10–35% of patients with postanoxic encephalopathy. It remains unclear which electrographic seizure patterns indicate possible recovery, and which are a mere reflection of severe ischemic encephalopathy, where treatment would be futile. We aimed to identify quantitative electroencephalography (EEG) features with prognostic significance. Methods From continuous EEG recordings of 47 patients with generalized electrographic status epilepticus after cardiac arrest, 5‐min epochs were selected every hour. Epochs were visually assessed and categorized into seven categories, including epileptiform discharges. Five quantitative measures were extracted, reflecting background continuity, discharge frequency, discharge periodicity, relative discharge power, and interdischarge waveform correlation. The best achieved outcome within 6 months after cardiac arrest was categorized as “good” (Cerebral Performance Category 1–2, i.e., no or moderate neurologic disability) or “poor” (CPC 3–5, i.e., severe disability, coma, or death). Results Ten patients (22%) had a good outcome. Status epilepticus in patients with good outcome started later (45 vs. 29 h after cardiac arrest, p < 0.001), more often ceased for at least 12 h (90% vs. 16%, p = 0.02), and was less often treated with antiepileptic drugs (30% vs. 73%, p = 0.02). Status epilepticus in patients with a good outcome always evolved from a continuous background pattern, as opposed to evolution from a discontinuous background pattern in 14 patients (38%) with a poor outcome. Epileptiform patterns of patients with good outcome had higher background continuity (1.00 vs. 0.83, p < 0.001), higher discharge frequency (1.63 vs. 0.90 Hz, p = 0.002), lower relative discharge power (0.29 vs. 0.40, p = 0.01), and lower discharge periodicity (0.32 vs. 0.45, p = 0.04). Significance Our results can be used to identify patients with possible recovery. We speculate that quantitative features associated with poor outcome reflect low neural network complexity, resulting from extensive ischemic damage.

Early electroencephalography for outcome prediction of postanoxic coma: A prospective cohort study

“…Sixty‐five percent of these patterns showed identical bursts . The second subgroup is generalized periodic discharges on a suppressed background . These results are in line with findings of our recent quantitative analysis, in which we showed that an amplitude ratio between nonsuppressed and suppressed segments of ≥6.12 is invariably associated with a poor outcome .…”

“…Otherwise, isoelectric or low‐voltage patterns at 24 hours after cardiac arrest were invariably associated with poor outcome . Time‐independent predictors of poor outcome were generalized periodic discharges on a suppressed background and burst suppression with identical bursts . Results on the prognostic value of other burst‐suppression patterns are conflicting …”

Clinically distinct electroencephalographic phenotypes of early myoclonus after cardiac arrest

“…Development of a continuous EEG background after cardiac arrest is associated with regaining consciousness and favorable neurological outcome. 23–25 The epileptiform discharges in these patients were not complex bursts, but rather single midline or parasagital spikes, implying a different generator than the bursts noted in Pattern 1. Finally, the Pattern 2 patients were clinically more likely to respond to addition of anticonvulsant medication, suggesting a degree of intact neuronal membranes and receptors.…”

Clinical neurophysiology for neurological prognostication of comatose patients after cardiac arrest

“…A recent elegant study illustrates that patients with early Lance-Adams syndrome, a stimulus-sensitive myoclonus with epileptiform EEG, who may reach a relatively good prognosis, display relatively tiny spike over the midline region superimposed on a continuous EEG background, as opposed to subjects with massive status myoclonus and dismal outcome that show burst-suppression backgrounds with polyphasic, high voltage and diffuse epileptiform features (Elmer et al, 2016). Quantitative analysis suggests that higher background continuity, higher discharge frequency, but lower discharge periodicity is also related to better outcome (Ruijter et al, 2015). It seems that these patients should be treated aggressively with large-spectrum anticonvulsants under EEG control and, if needed, pharmacological coma.…”