Using Generalized Polyspike Train to Predict Drug-Resistant Idiopathic Generalized Epilepsy

Abstract

Introduction: The authors tested the hypothesis that the EEG feature generalized polyspike train (GPT) is associated with drug-resistant idiopathic generalized epilepsy (IGE).

Methods: The authors conducted a single-center case-control study of patients with IGE who had outpatient EEGs performed between 2016 and 2020. The authors classified patients as drug-resistant or drug-responsive based on clinical review and in a masked manner reviewed EEG data for the presence and timing of GPT (a burst of generalized rhythmic spikes lasting less than 1 second) and other EEG features. A relationship between GPT and drug resistance was tested before and after controlling for EEG duration. The EEG duration needed to observe GPT was also calculated.

Results: One hundred three patients were included (70% drug-responsive and 30% drug-resistant patients). Generalized polyspike train was more prevalent in drug-resistant IGE (odds ratio, 3.8; 95% confidence interval, 1.3-11.4; P = 0.02). This finding persisted when controlling for EEG duration both with stratification and with survival analysis. A median of 6.5 hours (interquartile range, 0.5-12.7 hours) of EEG recording was required to capture the first occurrence of GPT.

Conclusions: The findings support the hypothesis that GPT is associated with drug-resistant IGE. Prolonged EEG recording is required to identify this feature. Thus, >24-hour EEG recording early in the evaluation of patients with IGE may facilitate prognostication.

FIG. 1.

Example of a single patient showing an occurrence of both GPFA (>1 second) and GPT (<1 second) in close temporal proximity on a bipolar montage (A) and average referential montage (B). In this example, the two electrographic features have similar morphology. GPFA, generalized paroxysmal fast activity; GPT, generalized polyspike train.

FIG. 2.

A, Histogram showing the distribution of total EEG durations across patients. Most patients had less than 1 hour of EEG recording. B, Kaplan–Meier curve showing the probability of a patient remaining without GPT as a function of recording duration. Check marks indicate the end times of EEG recording for each patient, taken as censoring times. GPT, generalized polyspike train.

FIG. 3.

A, The percentage of patients with each EEG feature whose feature occurred by a given time. Only patients who ever had the listed EEG feature are included. B, The percentage of patients with each EEG feature whose feature occurred within the first hour of recording. This is the proportion of patients in whom a routine outpatient EEG is expected to capture a feature, given that it is present in the patient. GPFA, generalized paroxysmal fast activity; GPT, generalized polyspike train; GSW, generalized spike-wave; PSW, polyspike-and-wave.