The importance of interictal electroencephalography in paroxysmal states

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.

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.

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.

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 (Tab. 4, Fig. 2, Ref. 14).