Selective electroencephalograph-guided microsurgical callosotomy for refractory generalized epilepsy.

Between 1978 and 1985, 35 patients with medically refractory multiform seizures were submitted for sections of variable portions of the corpus callosum. Guided by intraoperative electroencephalographic and electrocorticographic monitoring, the section was carried out only in the portion of callosum that was involved in the maintenance of the bilaterally synchronous slow spike and wave discharge (as documented by intraoperative electrocorticography). In our patients, only part of the frontal corpus callosum needed to be sectioned to interrupt the bilateral synchrony of epileptic discharge. Of the 35 patients, operated on, 28 have had an adequate long-term follow up and are presented herein. All had significant improvement in seizure frequency and psychosocial functioning.

Anterior callosotomy as a substitute for hemispherectomy.

Two patients with epilepsy and large hemispheric lesions underwent section of the frontal fibres of the corpus callosum for the treatment of seizures refractory to medical treatment. A severely retarded girl of 18 had encephalotrigeminal angiomatosis (Sturge-Weber syndrome) with multiple daily absences, tonic-clonic, myoclonic, atonic and adversive seizures since infancy. All types of fits--with the exception of adversive seizures and rare tonic-clonic fits--disappeared after anterior callosotomy. Another moderately retarded girl of 18 had an old cystic lesion over the entire territory of the left middle cerebral artery. She had had right hemiplegia since infancy and frequent brief absences and massive myoclonus triggered by unexpected sensory stimuli since the age of six years. Following anterior callosotomy there was an almost complete disappearance of the absences and a marked reduction of her startle myoclonus. Frontal callosotomy is a useful procedure in epileptics with large hemispheric lesions and carries less risk than hemispherectomy or total commissurotomy.

Anterior callosotomy in epileptics with multiform seizures and bilateral synchronous spike and wave EEG pattern.

Cerebral commissurotomy is a well established procedure in the treatment of epileptics refractory to drug therapy. Breeching of the ventricles in complete commissurotomy carries a certain morbidity. This has led others to perform operations in which the entire corpus callosum or only its anterior portion with or without the anterior commissure were sectioned. Sectioning of the anterior corpus callosum alone is justified by: a) frequent appearance in patients of seizures attributable to a frontal focus, b) clinical and experimental evidence that frontal discharges spread across the corpus callosum leading to subsequent generalized its, c) the attempt to understand the mechanisms involved in generalized seizures, d) even further reduced surgical morbidity and neuropsychological disability. Five epileptics were submitted to anterior callosotomy. The seizures in all of them suggested a frontal focus and consisted of absences, adversive, tonic, atonic, and tonic-clonic attacks. All patients were incapacitated by the frequency of seizures. Their EEGs showed paroxysms of bilateral synchronous slow spike and wave with uni-, or multiple (including bilateral symmetrical) focal accentuation. In two patients there were additional independent temporal lobe discharges. Neuropsychological evaluation showed cognitive deficits caused by inattention paroxysms and absences. After anterior callosotomy there was marked reduction in frequency of all types of seizures, the greatest improvement being in the reduction of frequency of absences. There was a marked decrease in physical, social and neuropsychological disabilities.