The value of ictal clinical manifestations in differentiating frontal and temporal lobe partial epilepsies was determined in a prospective study of 252 patients selected according to imaging, EEG, and focal clinical patterns from records at the National Hospital for Neurology and Neurosurgery, London, UK. Cluster analysis gave 14 distinctive clinical types of patterns, but these had limited localizing value with the exception of perirolandic seizures. Two seizure types with prominent, early motor manifestations, especially version and posturing, were associated with frontal lobe abnormalities. Very high seizure frequencies were seen more often with frontal lesions. Seizures associated with temporal lobe lesions were characterized by absences and those with subjective onsets such as fear and oroalimentary automatisms. Location of interictal EEG spikes and ictal EEG onsets were generally consistent with lesion sites. Relatively few seizures could be localized reliably on clinical grounds. [1]

COMMENT. The ILAE classification of seizure types based on electroclinical criteria may be justified for well-defined syndromes, eg benign epilepsy of childhood with centrotemporal spikes, but in the differentiation of frontal and temporal lobe partial epilepsies in adults there is significant clinical/pathological overlap. The authors argue in favor of an anatomical-pathological definition of fronto-temporal seizures, and they disagree with the ILAE classification of 7 different localizable seizure types within the frontal lobes based on electroclinical manifestations. Neuroimaging appears to be the only reliable method of lesion localization for frontal and temporal lobe partial epilepsies.

Magnetoencephalographic analysis of rolandic discharges in benign childhood epilepsy is reported from Kyushi University, Fukuoka, Japan [2]. Dipole methods of MEG allow more precise location and quantification of electrically active brain regions compared to the EEG, and the recorded signal reflects intracellular rather than extracellular current flow. Equivalent current dipoles (ECDs) of prominent negative sharp waves of rolandic discharges appeared as tangential dipoles in the rolandic region and showed a limited localization compared with other components. ECDs of preceding small positive waves, positive waves following negative sharp waves, and negative slow waves were located close to negative sharp waves. ECDs of rolandic discharges were localized to the origin of somatosensory evoked magnetic field stimulated at the lower lip on a reconstructed three-dimensional MR image. Rolandic discharges are generated by a similar mechanism to that for the somatosensory evoked responses.