Callosotomy in West syndrome suggests a cortical origin of hypsarrhythmia.

Hypsarrhythmia and spasms of West syndrome have been postulated by some investigators to have a brainstem origin. Cortical involvement is also postulated because of the frequent association with cortical lesions. Cortical discharges have been proposed to stimulate subcortical structures (i.e., brainstem) and hypsarrhythmia is a secondarily generalized phenomenon produced by the brainstem. Two children with cryptogenic West syndrome refractory for several years to steroids and conventional antiepileptic drugs underwent total callosotomy. Hypsarrhythmia that was bilateral before operation became unilateral after the procedure and spasms became asymmetrical, suggesting that a corticocortical pathway through the corpus callosum is important in the generalization of hypsarrhythmia.