Clinical and functional characteristics of children with benign epileptiform discharges on the electroencephalogram and epileptic seizures
BACKGROUND: Eight to 12% of patients with benign epileptiform discharges of childhood (BEDC) on the electroencephalogram (EEG) develop epileptic seizures. A significant proportion of these patients have cognitive impairment. The issue of determining comprehensive predictors of epileptic seizures and cognitive impairment in patients with BEDC on the EEG remains unresolved. AIM: To analyze the relationship between BEDC and epileptic seizures and also to evaluate their impact on the cognitive status of patients. METHODS: The study involved 99 patients aged from 5 to 15 years (61 boys and 38 girls, mean age 9.3 years, standard error of the mean 0.23) with epileptic seizures (n = 57) and without them (n = 42). The following epilepsy types were recorded: age-dependent focal (n = 33, 58%), structural focal (n = 10, 18%), epileptic encephalopathy (n = 14, 24%). After therapy adjustment, patients received 1 anticonvulsant (54%), 2 anticonvulsants (26%), or 3 anticonvulsants (19%). The following anticonvulsants (in duo- and polytherapy, the main prescribed anticonvulsant was specified at the highest dose) were used: lamotrigine (n = 8), levetiracetam (n = 24), valproic acid (n = 13); in single cases, in combination with other drugs: ethosuximide (n = 2), topiramate (n = 1), oxcarbazepine (n = 1). The cognitive sphere was assessed on the EpiTrack Junior test scales, the P300 potential was recorded in the oddball paradigm. RESULTS: The group of patients with epileptic seizures demonstrated a lower total score in the 'Words' test (4 [3; 5] versus 5 [4; 5]), the higher power of theta- and alpha-oscillations and lower frequency of alpha-oscillations on the EEG; in the same group, higher latency of N2 component of P300 was identified in Fz. The association between the number of taken anticonvulsants and the extent of cognitive impairments was assessed: children receiving 3 anticonvulsants showed lower scores on scale 1 of the EpiTrack test (2 [1; 3]) compared to children taking 1 or 2 anticonvulsants (4 [3; 5] and 4 [1; 5] respectively). The lowest results were recorded in patients receiving preparations of valproic acid. Logit regression analysis of neurophysiological parameters: χ2 indicator for the model was 8.7; p = 0.013; Hook–Jeevis estimation method; loss function — maximum likelihood; the number of correct classifications into group 1 was 86%, into group 2 — 69%; odds ratio — 4.52. CONCLUSIONS: Correlates and predictors of the presence of epileptic seizures in patients with BEDC on the EEG can be the neurophysiological parameters of stimulus recognition based on P300 potential and average alpha rhythm frequency data. In patients with BEDC on the EEG and manifestation of epileptic seizures, the most pronounced cognitive impairment was observed in the group of patients with epileptic encephalopathy and structural focal epilepsy.