The response to corpus callosal section in 64 patients with intractable epilepsy was evaluated in a multicenter study in Australia. Age at time of operation ranged from 3 years to 47 years (mean age 20 years); 43% underwent callosotomy during childhood, at age <16 years. Mean age of onset of epilepsy was 5 years, and mean duration of epilepsy before surgery was 15 years. The most common seizure patterns were generalized tonic-clonic (GTC) (83%) and drop attacks (73%). Focal seizures occurred in 42%, of whom half had seizures of frontal lobe origin. The rate of favorable outcome was 60% for drop attacks, 47% for tonic seizures, 49% for GTCs, and 55% for complex partial seizures. Outcome for drop attacks was more favorable with unilateral seizure activity or generalized slow spike and wave, characteristic of Lennox-Gastaut syndrome; bilateral independent spikes, and severe mental retardation carried a poor prognosis. Improvement followed complete callosotomy in 6 of 10 patients not benefited by anterior callosotomy. 
COMMENT. In children with medically intractable epilepsy, especially drop attacks of focal or Lennox Gastaut types and CPS of frontal lobe origin, corpus callosotomy should be considered when focal resection is not appropriate. Surgical complications are reported to be mild, and include transient hemiparesis and mutism.
Satisfactory seizure control is reported in 25 (74%) of 34 children following corpus callosotomy performed at the Institute of Neurology, Goiania, Brazil . The majority had mental retardation. Atonic seizures responded best, followed by tonic, GTC, and atypical absence seizures. CPS and myoclonic seizures were not controlled. Of 26 patients with behavior problems, 81% had a significant decrease in aggressiveness, hyperactivity, and/or attention deficit. Total section was complicated by interhemispheric disconnection symptoms. Mutism, dysarthria, or gait dyspraxia persisted in 5 of 13 patients affected. Section limited to the anterior two thirds was uncomplicated. The neurophysiological basis for corpus callosotomy is the interruption of bilateral ictal synchrony.