Abstracts

Rationale: Postasphyxial neonatal seizures often respond poorly to antiepileptic drug (AED) therapy. The factors associated with higher seizure burdens and AED refractoriness in neonates with hypoxic ischemic encephalopathy (HIE) are poorly understood. Whether electrographic seizures independently predict poor outcome is a controversial issue. This study aims to assess the relationships between postasphyxial electrographic seizure characteristics, EEG background, and clinical outcome through detailed analysis of continuous EEG monitoring (cEEG) data. With this we expect to refine prognostication and also to better guide clinicians during treatment of postasphyxial seizures Methods: EEG background and seizure characteristics were studied in 42 (out of 119 with HIE) consecutive term neonates with postasphyxial seizures using video-EEG for ≥24 hours, starting <24h post partum. Electrographic seizures were aggressively treated with AED according to protocol. An eight-grade EEG background score was developed. MRI brain done in 39 were compared with those from a control group of 36 neonates with HIE who had cEEG during the same period and no seizures recorded. For statistical analyses, patients with seizures were grouped into those with mild to moderate (group I, grades 1-5, n=20) and severe (group II, grades 6-8, n=22) abnormalities of EEG background. Survivors were followed for at least two years. Results: Increasing total seizure number (rho 0.73, p<0.001) and total seizure burden in minutes (rho 0.41, p<0.01) were strongly correlated with worsening EEG background. The median seizure burden was significantly increased in EEG group II [109.3 (range 17.5-468.7) versus 44.6 (range 5.1-370.9) minutes, p= 0.03] as was the number of neonates showing injury to thalamus and basal ganglia on MRI (16/22 versus 3/20, p<0.001), when compared to EEG group I. Logistic regression analysis showed that EEG background strongly predicted (p=0.003) poor outcome, defined as death or severe disability. Neither total seizure number, burden, nor MRI confirmation of lesions of thalami and basal ganglia significantly added to this. Compared to the seizure group, significantly more patients in the non-seizure group had relative sparing of the cerebral cortex on MRI (10/36 versus 3/39, p=0.03). Conclusions: In neonates with HIE, higher electrographic seizure burdens and AED refractoriness occur in the context of more severe brain injury as reflected by the EEG background and MRI abnormalities. Relative sparing of cerebral cortex is seen in neonates with HIE and no seizures. In future studies of treatment of postasphyxial neonatal seizures, patient stratification according severity of underlying encephalopathy and brain injury pattern is indicated.