Averaged EEG spike dipole analysis may predict atypical outcome in Benign Childhood Epilepsy with Centrotemporal Spikes (BCECTS)

Abstract

Purpose

Benign Childhood Epilepsy with Centrotemporal Spikes (BCECTS) is the most common childhood idiopathic focal epilepsy with a good outcome. However, an increasing number of reports suggest a ‘not so benign’ outcome showing atypical evolution.

Methods

We analyzed the electroencephalographic (EEG) spike source dipoles of BCECTS patients to compare patients with confirmed typical and atypical outcome showing intractable epilepsy and cognitive decline. Thirty-seven patients that were diagnosed for BCECTS and whose clinical information was sufficient enough to confirm long-term outcome were included in the study. Eight patients (22%, 7 patients for poor seizure control and 1 patient for cognitive decline) were classified as showing atypical outcome. Forty-seven averaged spike dipole sources were analyzed using the single equivalent current dipole (ECD) method. The inverse problem was solved using the 4 shells ellipsoidal model.

Results

The coordinate value of y_ori differed significantly between the two groups (mean ± standard deviation, 0.32 ± 0.33 for the typical group and −0.33 ± 0.77 for the atypical group, P < 0.001). These findings suggest that the averaged spike source dipoles were oriented anteriorly in patients with typical outcome and posteriorly in patients with atypical outcome. Spike source dipoles seemed to be located higher in patients with atypical presentation but this finding was insignificant.

Conclusion

We can conclude that there are significant differences in spike source dipole in patients with BCECTS that shows atypical outcome, and we can use this finding as a marker for predicting an outcome at the time of diagnosis.

Introduction

Benign Childhood Epilepsy with Centrotemporal Spikes (BCECTS) is the most frequent idiopathic focal epilepsy in childhood and the most frequent epilepsy syndrome in school-aged children [1]. Seizures arise from the Rolandic area and interictal spike discharges are very frequently observed in this region. It is a well-recognized electroclinical syndrome by the International League Against Epilepsy (ILAE) with Rolandic seizures, centrotemporal spikes, and a good outcome [2]. Infrequent nocturnal seizures and good seizure control is the characteristic finding that has led to the nomenclature of “benign” in BCECTS. Since the onset is just before or after the child begins to attend school, and the worrisome side effect of anticonvulsant on cognition, decision on starting medication is often difficult for both neurologists and parents [3].

Recently there were reports on atypical evolution and a poor outcome in patients with BCECTS [4], [5]. Some patients initially diagnosed as BCECTS had poor seizure control and thus intractable epilepsy and a significant portion of patients showing language disability, behavioral problems, or other cognitive dysfunctions. There were efforts to find factors that could predict atypical evolution. Findings from an electroencephalogram (EEG) such as focal slowing, bilateral spikes, or location of spike were proposed as candidates for atypical progression [6]. A study using magnetoencephalography (MEG) in patients with BCECTS showed a different spike source location and orientation in patients with atypical evolution [7]. However, an MEG is not routinely used in the clinical practice of benign epilepsy management and it is also costly.

The purpose of this study was to analyze averaged spike dipole source in patients showing typical and atypical outcome in patients with BCECTS using an EEG of which we universally and easily use in the diagnosis of epilepsy. If there is any difference between the 2 groups, we can use this finding to predict outcome at the time of diagnosis even before the initiation of treatment.