Callosotomy for severe epilepsies with generalized seizures: outcome and prognostic factors

The purpose of the present study was to verify the effect of callosotomy on generalized seizures, to check the effect on other seizure types and to search for possible prognostic factors. Twenty patients with a minimum follow-up of one year (mean 3.5 years) were available for our analysis. In six of them the callosotomy was performed in two stages (total: 26 surgical procedures). Age ranged from 14 to 40 years (mean 23 years). Different aetiologies were known in 15 patients. Duration of epilepsy ranged from 6 to 23 years (mean 15 years). The frequency of seizures ranged between 19 and 750 per month. The most significant effect of surgery was the complete suppression of the generalized seizures associated with falling in 9/19 and their reduction of more than 80% in 7/19 patients (total "good results": 16/19). The generalized tonic-clonic seizures were less affected. The surgical effect on the partial seizures was very variable, the partial simple seizures being the most affected. A positive statistical association with the outcome of the generalized seizures with fall was found for a presurgical seizure frequency below 90 per month, a prevalent bilateral EEG epileptic activity and, to a less extent, the absence of cerebral structural lesions. The role of age, aetiology, duration of the disease, single or more seizure types, mental impairment and extent of callosotomy remains uncertain. Disconnection syndrome does not appear if the splenium is spared. The present findings confirm that the main indication for callosotomy is the occurrence of generalized seizures with fall. Surgery can be initially limited to the anterior 2/3 of the corpus callosum; further posterior section of the corpus, excluding the splenium, should be regarded as a second step, when necessary.