Quantitative EEG Characteristics of Periodic Lateralized Epileptiform Discharges according to Benzodiazepine Responsiveness

ABSTRACT

BACKGROUND: Periodic lateralized epileptiform discharges (PLEDs) are associated with altered consciousness in 75% of patients. Major controversy about PLEDs is whether they are ictal or interictal phenomenon. Diagnosis of non-convulsive status epilepticus is often guided by response to benzodiazepine. We conducted a study to evaluate quantitative differences of EEG activity with PLEDs according to their response to acute benzodiazepine trial. METHODS: Nineteen patients with altered consciousness (stupor or coma) for whom the electroencephalography (EEG) recording with acute benzodiazepine trial was undertaken within 24 hours of onset of altered consciousness were retrospectively enrolled. Morphology of PLEDs including amplitude, frequency, and variability of the frequency was analyzed. Quantitative analysis of EEGs includes spectral power, spectral coherence, and graph theory analysis. Results of the analyses were compared between patients whose PLEDs were abolished by benzodiazepine (BDZ-R group) and those whose PLEDs persisted (BDZ-NR group). RESULTS: Morphologic variables were not different between two groups. In BDZ-R group, alpha-1 activity was increased in both frontopolar areas. Beta activity was also increased in both frontal areas while delta activity was reduced. In BDZ-R group, alpha-1 and beta activities were more coherent between bilateral hemispheres in frontal, anterior temporal, and central areas. Coherence line topographic map also revealed more bilaterally symmetric pattern in BDZ-R group. Network characteristics revealed by graph theory analysis did not differ between the two groups. CONCLUSIONS: Greater higher frequency activity (alpha-1 and beta) and lesser lower frequency activity (delta) in frontal areas, and more coherent activity in higher frequency band between hemispheres were associated with benzodiazepine responsiveness.