Delineating behavioral and cognitive phenotypes in juvenile myoclonic epilepsy: Are we missing the forest for the trees?

INTRODUCTION

Patients with juvenile myoclonic epilepsy (JME) have executive dysfunction and impulsive traits. There are lines of evidence that JME is a heterogeneous epilepsy syndrome considering outcome. In this study, we aimed to analyze this heterogeneity beyond seizure control. The objective was to identify whether the pattern of cognitive dysfunction and impulse control is also heterogeneous, in an attempt to establish possible differences in patients with easy- and hard-to-control epilepsies.

METHODS

Essentially, 57 patients with JME were compared with 44 controls. Patients and controls were assessed with a neuropsychological battery for executive, attention, and memory functions. The expression of impulsive traits was evaluated with the Temperament and Character Inventory - novelty seeking domain. Then, patients were categorized according to seizure control as having easy- and hard-to-control JME.

RESULTS

Patients with hard-to-control JME showed worse performance in 12 out of 25 neuropsychological tests than those with easy-to-control JME. Patients with hard-to-control JME also demonstrated significantly higher scores in novelty seeking - subfactor impulsiveness (p=0.002).

SIGNIFICANCE

Our study demonstrated the existence of distinct or more severe cognitive and psychiatric profiles in a subset of patients with JME. Patients with treatment-refractory seizures seem to present a broader impairment related to both cognitive deficits and impulsive traits. These findings suggest that patients with JME are not equally compromised by executive and memory deficits or dysfunction, neither by their impulsive traits. Thus, there is a need for a better characterization of patients with JME to include diverse phenotypes since our results suggest a possible existence of distinct groups of patients with JME.