How generalized are secondarily “generalized” tonic-clonic seizures?
In clinical practice epileptic seizures with focal onset and subsequent generalized motor involvement are referred to as secondarily generalized seizures. The purpose of this study is to investigate the degree of electrophysiological generalization in seizures that are clinically secondary generalized. Intracranial EEG recordings of secondarily generalized tonic-clonic seizures were visually and quantitatively analysed for the presence of epileptiform activity. In 24 (26%) of 93 seizures recorded from 17 (27%) of 64 patients intracranial EEG channels were found that never recorded epileptiform activity during secondarily generalized tonic-clonic seizures. Our results demonstrate that seizures that are secondary generalized clinically are not always generalized electrophysiologically. This may have therapeutic implications.
