The importance of interictal electroencephalography in paroxysmal states

Abstract

Introduction: Electroencephalography (EEG) is a non-invasive investigation method playing an important role in differential diagnostics of seizures. In this article authors point out to its importance, but also limitations. Material and methods: Native interictal EEG findings were evaluated in inpatients after solitary unprovoked epileptic seizures (n=84), patients with sporadic epileptic seizures (n=179), patients with "chronic" epilepsy (n=324), outpatients with epilepsy (n=300), patients with syncope (n=100), patients with neurocardiogenic syncope (n=70), patients with migraine (n=100) and patients with tetanic syndrome (n=100). EEG findings were evaluated as normal or abnormal and abnormal findings were further divided into epileptic and non-epileptic, focal and generalized. Results: In native EEG, epileptic manifestations were registered in 14.29 % of patients after solitary unprovoked epileptic seizures, in 25.7 % of patients with sporadic epileptic seizures, in 37.34 % of patients with chronic epilepsy and in 32 % of outpatients with epilepsy. Interictal EEG abnormalities (epileptiform and non-epileptiform) in non-epileptic diagnoses were at least registered in patients with syncope, but also in this group abnormal findings occurred in 30 % of them. We registered epileptiform abnormalities in 5 % of patients with migraine, in 4 % of patients with tetanic syndrome and in 2 % of patients with syncope. Conclusion: The diagnosis of epilepsy and non-epileptic seizures is a only a clinical diagnosis. EEG is a very important investigational method in this group of patients, but still only additional.