Clinical outcome of generalized periodic epileptiform discharges on first EEG in patients with hypoxic encephalopathy postcardiac arrest.

INTRODUCTION: The EEG, alongside clinical examination, imaging studies, and SSEPs, is used to determine the prognosis following hypoxic encephalopathy postcardiac arrest. Generalized periodic epileptiform discharges (GPEDs) are recognized as a "malignant" EEG pattern associated with very poor outcome with previous studies reporting no or few survivors. We looked at our database of cardiac arrest patients who subsequently developed GPEDs to determine clinical outcome and profile any survivors. METHODOLOGY: We identified all cardiac arrest patients treated at King's College Hospital between 2011-2014 who developed hypoxic encephalopathy associated with GPEDs, BiPLEDs (bilateral periodic lateralized epileptiform discharges), and periodic discharges on first EEG. We collected clinical data including age, gender, downtime, EEG reactivity, presence of seizures or myoclonus, and outcome. Survivors were defined as patients who were discharged from the hospital to home or a neurorehabilitation unit. RESULTS: Thirty-six postcardiac arrest patients with hypoxic encephalopathy were identified, 24/36 with GPEDs, and 12/36 with BiPLEDs on first EEG. The mean age of patients was 62.8 ± 14.5 years old, with 27 males (75%) and 9 females (25%). Ten of thirty-six patients survived, which is slightly higher than previously reported. Statistical tests to compare clinical characteristics between survivors and nonsurvivors demonstrated no significant differences except for trend to significance for the presence of reactivity on first EEG (p = 0.0794). On discharge, one survivor had good functional outcome (and subsequently became independent), but all others were dependent for all ADLs (activities of daily living). CONCLUSION: Generalized periodic epileptiform discharges carry a grave clinical prognosis following cardiac arrest. This study did identify a higher number of survivors compared to previous studies, but most were severely disabled at hospital discharge. Reactivity of the first EEG might predict better prognosis and merit further evaluation. This article is part of a Special Issue entitled "Status Epilepticus".

Periodic EEG patterns: importance of their recognition and clinical significance / Padrões eletrencefalográficos periódicos: importância do seu reconhecimento e significado clínico

Periodic electroencephalographic (EEG) patterns consist of discharges usually epileptiform in appearance, which occur at regular intervals, in critical patients. They are commonly classified as periodic lateralized epileptiform discharges (PLEDs), bilateral independent PLEDs or BIPLEDs, generalized epileptiform discharges (GPEDs) and triphasic waves. Stimulus-induced rhythmic, periodic or ictal discharges (SIRPIDs) are peculiar EEG patterns, which may be present as periodic discharges. The aim of this study is to make a review of the periodic EEG patterns, emphasizing the importance of their recognition and clinical significance. The clinical significance of the periodic EEG patterns is uncertain, it is related to a variety of etiologies, and many authors suggest that these patterns are unequivocally epileptogenic in some cases. Their recognition and classification are important to establish an accurate correlation between clinical, neurological, laboratorial and neuroimaging data with the EEG results.

Padrões eletrencefalográficos (EEG) periódicos consistem em descargas geralmente epileptiformes em aparência, que ocorrem a intervalos regulares, em pacientes críticos. Esses padrões são habitualmente classificados como descargas epileptiformes periódicas lateralizadas (PLEDs), PLEDs bilaterais e independentes ou BIPLEDs, descargas epileptiformes periódicas generalizadas (GPEDs) e ondas trifásicas. Descargas rítmicas, periódicas ou ictais induzidas por estímulos (SIRPIDs) são padrões eletrencefalográficos peculiares, que podem se apresentar como descargas periódicas. O objetivo deste estudo é fazer uma revisão dos padrões EEG periódicos, enfatizando a importância do seu reconhecimento e seu significado clínico. O significado clínico dos padrões EEG periódicos é incerto. Está relacionado a uma variedade de etiologias e muitos autores sugerem que tais padrões sejam inequivocamente de natureza epileptogênica em alguns casos. O seu reconhecimento e classificação são importantes para estabelecer uma correlação acurada entre dados clínicos, neurológicos, laboratoriais e de neuroimagem com os resultados de EEG.