Focal features in patients with idiopathic generalized epilepsy

The stringent dichotomy between focal and generalized epilepsies has become a contentious issue, since neuropathological studies as well as structural and functional imaging data hypothesized the existence of focal brain abnormalities in patients with well-documented idiopathic generalized epilepsy. The aim of our study was to investigate whether clinical and EEG features generally considered typical for a focal seizure disorder also occur in patients with generalized epilepsies to further support the hypothesis of a more continuous transition between focal and generalized epilepsies in contrast to the present concept of a stringent pathophysiologic dichotomy.

We retrospectively studied 20 consecutive patients with idiopathic generalized epilepsy who underwent video EEG monitoring either because of uncertainty of their epilepsy syndrome or because of a difficult to treat epilepsy. We determined the incidence of (a) focal interictal epileptiform discharges (IEDs), (b) intermittent temporal slow waves, and (c) clinical signs that are widely accepted as typical for a focal seizure onset, i.e. version, tonic/dystonic unilateral posturing, postictal hemiparesis, postictal nose wiping and figure of 4.

Focal IEDs occurred in seven patients (35.0%), intermittent temporal slow waves in six (30%), and clinical signs pointing towards a focal seizure onset were found in seven patients (35%).

Our study of EEG and clinical data supports the more sophisticated previous investigations in which structural and functional imaging as well as histopathological data suggested the presence of focal brain abnormalities in patients with 'generalized' epilepsies. Furthermore we emphasize the cautious use of isolated focal EEG abnormalities and certain clinical signs to prevent a premature diagnosis of focal epilepsy in patients who may indeed suffer from a generalized seizure disorder.