[Investigation of epilepsy. Magnetic tomography more and more important as a diagnostic technique]

Electroencephalography (EEG) and neuroradiology are both indispensible techniques in cases of suspected epileptic seizure, when the aim of investigation is to determine whether the seizure was of epileptic nature, and if so whether it was the result of specific provocative factors or an expression of epileptic disease. In the latter case, the epileptic condition should be classified and its aetiology determined, if possible. Routine or sleep EEG providing interictal epileptiform discharges is a useful aid to differential diagnosis. To obtain EEG recordings during actual seizures, long-term recordings, using either ambulatory equipment or an EEG-video procedure, are usually used. The combination of EEG and video recording, using surface or surgically implanted electrodes, is a procedure of major importance in the evaluation of patients refractory to medical treatment and possible candidates for epilepsy surgery. In cases of epilepsy suspected to be caused by tumour or cerebrovascular disease, neurological investigation does not differ from that routinely used in such conditions. MRI (magnetic resonance imaging) techniques have become important aids in the preoperative work-up in cases of chronic therapy-resistant partial epilepsy. MRI has also simplified the identification of minor morphological abnormalities causing partial epilepsy, and is the method of choice in such cases. The sensitivity of MRI is improved by its combination with volumetric measurements and spectroscopy. The use of functional neuroimaging with SPECT (single photon emission computed tomography) and PET (positron emission tomography) during seizures provides further information. A promising new development is the co-registration of MRI and functional imaging (dipolar reconstruction of EEG spikes and seizure patterns, SPECT, PET). MRI is a cornerstone of the preoperative work-up, but diagnosis and the choice of therapeutic approach is always based on the clinical picture, EEG, and functional and morphological imaging.