Intractable frontal lobe epilepsy: pathological and MRI features

The clinical, pathological, and at least one year follow-up of 48 patients with intractable frontal lobe partial epilepsy who underwent surgical treatment for their seizure disorder were reviewed. The group consisted of 27 males and 21 females. Preoperative magnetic resonance imaging (MRI) was normal (26 patients), demonstrated focal frontal lobe (16 patients) or multilobar signal abnormalities (6 patients). Postoperatively patients were divided into one of four groups based upon the degree of seizure activity (Class I: seizure free, Class IV: little to no improvement, Classes II/III: intermediate). Eight patients with tumors (low grade gliomas) were Class I (N = 6) or Class II (N = 2) postoperatively. The remaining six patients with focal, completely resected pathological lesions (e.g. tubers, contusions, etc.) also had Class I or Class II outcomes. Of the 31 patients with the pathological diagnosis of gliosis, the outcome was dependent on the MRI appearance. Preoperative MRI scans of these patients were normal (N = 23), or had focal frontal lobe (N = 2) or multilobar (N = 6) abnormalities. The gliosis patients with unilateral frontal MRI lesions had a good outcome (Class I or II) while those with multilobar MRI abnormalities were all Class IV. Successful outcome correlated strongly with both focal frontal lobe MRI and pathological abnormalities in contrast to the less favorable results seen in patients with normal head MRI scans and gliosis or no pathological abnormality on pathological examination. Multilobar MRI abnormalities invariably had the poorest outcome of all patient groups. Thus presurgical MRI is an important tool and predictor of surgical outcome in patients with frontal lobe epilepsy.