Abnormal quantitative EEG scores identify patients with complicated idiopathic generalised epilepsy

To investigate the relationship between quantitative EEG (QEEG) scores and "complicating factors" (psychopathology, true pharmacoresistance, neurological symptoms) in idiopathic generalised epilepsy (IGE).

35 newly referred, newly diagnosed, unmedicated IGE patients were collected in a prospective and random manner. Standard neuro-psychiatric and EEG examination was done. The patients were treated and controlled at regular visits. After 2 years of follow-up, clinical data were summarised and were compared to QEEG results. Clinical target items were neurologic and psychiatric abnormalities, proven pharmacoresistance. Patients with at least one of these items were labelled "complicated", whereas patients without these additional handicap were labelled as "uncomplicated". The 12 QEEG target variables were: Z-transformed absolute power values for three (anterior, central, posterior) brain regions and four frequency bands (1.5-3.5; 3.5-7.5; 7.5-12.5; 12.5-25.0 Hz). QEEG scores outside the +/- 2.5 Z range were accepted as abnormal. The overall QEEG result was classified as normal (0-2 abnormal scores), or pathological (3 or more abnormal scores). Clinical and QEEG results were correlated.

All patients with psychopathology showed 4-8 positive pathological scores (power excess not confined to a single cortical region or frequency band). The two patients with pure pharmacoresistance showed pathological negative values (delta power deficit) all over the scalp. Statistically significant (P < 0.001) association was found between patients with uncomplicated IGE and normal QEEG, and between complicated IGE and pathological QEEG. Patients with neurological items had normal QEEG.

Higher degree of cortical dysfunction (as assessed in the clinical setting) is reflected by higher degree of QEEG abnormalities. QEEG analysis can differentiate between IGE patients with or without psychopathology. Forecasting psychopathology may be the practical application of the findings.