Clinical ictal symptomatology and anatomical lesions: Their relationships in severe partial epilepsy

High-resolution imaging techniques can demonstrate anatomic alterations in most patients identified as candidates for surgical treatment of their part ial epilepsy. The demonstration of an anatomic lesion is only one step in t he presurgical diagnostic procedure, which includes video-EEG and, when nec essary, video-stereo-EEG recordings of seizures. A review of the Literature shows that the simple removal of the magnetic resonance imaging (MRI)-evid ent lesion ("lesionectomy") reduces but does not completely suppress seizur es in a large percentage of patients, especially those with neuronal migrat ion disorders. This phenomenon could, at least in part, be explained by pre liminary data (in 33 patients) showing that less than 20% of seizures corre spond to a well-localized, intralesional discharge in about 40% of stereo-E EG-investigated patients with at least one intralesional electrode. The aut hors illustrate some anatomo-electroclinical examples of individual variabi lity of the ictal symptomatology, raising the problem of the decision about the extent of the surgical removal. Recent histologic and immunohistochemi cal studies have demonstrated several kinds of structural alterations in th e stereo-EEG-defined epileptogenic zone, not always overlapping with the MR I-visible lesion. This aspect can further explain some failures of MRI-guid ed lesionectomies. That relationships between "lesions" and epileptogenic z ones may be variable is also suggested by reports of patients who present w ith multiple lesions (i.e., cavernous angiomas, Bourneville syndrome) and a re cured by removal of only one of them.