Corpus callosum section and other disconnection procedures for medically intractable epilepsy

Corpus callosum section for carefully selected patients with uncontrolled epilepsy has become more acceptable as operative complications have decreased. From consideration of anatomical pathways utilized in the spread of seizure discharges, section of the corpus callosum is expected to decrease, but not abolish, bilaterally synchronous EEG abnormalities arising from most cerebral locations, perhaps excluding the temporal lobe. Clinical experience confirms this expectation. Persistence of some bilateral synchrony, presumably through subcortical relays, does not usually diminish the effectiveness of corpus callosum section on clinically generalized seizures that are eliminated or markedly decreased in 85% of patients after total corpus callosum section. Generalized seizure types that respond include tonic, atonic, tonic-clonic, and absence seizures. Patients who continue to have generalized seizures usually have low IQ and perhaps extensive bilateral cerebral involvement increases the extent to which subcortical structures participate in generalization. Complex partial seizures may cease, usually in patients with well-circumscribed, often extratemporal seizure foci. Focal seizures intensify in 25% of patients; a predictable consequence of sectioning interhemispheric inhibitory connections. Permanent disconnection syndromes, which are only rarely symptomatic, include sensory disconnection after posterior section, and split-brain syndrome after total section. A small percentage of patients develop impairments in language, motor, or memory functions. Language and motor deficits are predicted by pre-existing unilateral mild or moderate central nervous system damage. Partial section of the corpus callosum produces control of generalized seizures half as frequently as complete section. Neurologic sequelae of partial section occur nearly as frequently but are less severe.