EEG in Adult‐onset Idiopathic Generalized Epilepsy

Abstract

Summary:Purpose: It remains controversial whether adultonset idiopathic generalized epilepsy (IGE) is a distinct syndrome or a continuum among IGE syndromes. EEG is the only known biologic marker of IGE and helps differentiate many of its classic subsyndromes. In this study, we looked for the differences in the EEG findings of IGE of classic adolescent onset versus adult onset that may suggest syndromic heterogeneity.Methods: Seventy-six patients (47 adolescent-onset IGE, 29 adult-onset IGE) with a clinical and EEG diagnosis of IGE were included. We defined IGE with age at onset of 11-20 years as adolescent-onset IGE and age at onset of 20 years or after as adult-onset IGE. Patients with first-decade onset of seizures, delayed EEGs, and no EEG available for review were excluded. The first EEG was performed within 24 h of the seizure, and if negative, a sleep-deprived EEG was done. All EEGs were reviewed in detail with respect to the background activity and the generalized spike-wave (GSW) characteristic.Results: EEGs (87; 56 adolescent-onset IGE, 31 adult-onset IGE) were systematically reviewed. Background was normal in all patients. The morphology, amplitude, duration, frequency, occurrence, or activation of the GSW pattern did not differ between these two groups.Conclusions: No differences of EEG features were found between the classic adolescent-onset and the adult-onset IGE. This supports the hypothesis that they share common biologic determinants and exist along a life-long age spectrum of classic IGE.

Diagnostic yield of five minutes compared to three minutes hyperventilation during electroencephalography

“…This is in accordance with previous studies on the diagnostic yield of HV during EEG [2,[7][8][9][10][11].…”

“…In most of these studies the duration of the HV was 3 min [2,7,8], in one study it was 4 min [9], and in another study 5 min HV was performed [10]. The duration of the HV varied between 3 and 7 min in a recently published study [11].…”

A clinical study of syndromes of idiopathic (genetic) generalized epilepsy

“…These latter statements are often true in ictal recordings, but in most instances we do not need ictal recording, that often mandates a long-term video-EEG monitoring, to make a diagnosis in patients with IGE. In a previous report, there was no EEG difference between classic adolescent-onset IGEs and adult-onset IGEs [14]. Clinical expression depends on more than the EEG and the nature of the cortical discharges alone does not determine the seizure type or course [15].…”

EEG in the diagnosis, classification, and management of patients with epilepsy

“…Some caution is required when setting age limits to EEG investigation in adults, as idiopathic generalised epilepsies can present beyond adolescence. 13 Late onset IGE has the same electroclinical features as younger onset cases, 14 and the diagnosis will be missed if EEG is not requested, in the assumption that all new onset generalised seizures in adults are secondary to partial epilepsy.…”