Corpus callosotomy (or corpus callosum transsection) is a procedure that severs the membrane that divides the right and left cerebral hemispheres. This interferes with the electrical propagation of a seizure between the two halves of the brain. It does not directly remove the seizure focus but decreases the severity of the resulting event. This technique is performed in patients with sudden generalized seizures producing falls and injuries from "drop attacks". Other patients considered for this procedure have partial seizures arising from multiple independent sites in the brain with very rapid spread to the entire brain such as Lennox-Gastaut syndrome. Corpus callosotomy helps to reduce the severity and limit the spread of seizures in patients with multi-focal onsets and rapid generalized spread patterns for which other management is inappropriate. Its success in improving the seizures is over 50%. The generalized seizures and drop attacks tend to improve markedly.
Complications of corpus callosotomy are greater than with frontal or temporal lobe surgery. Behavioral, language, and other problems may affect function and the quality of life, but serious problems are temporary or uncommon. The potential risks of callosotomy must be weighed against its possible benefits, such as a reduction in the frequency of seizures that cause injury and other problems. The persons most susceptible to behavioral problems after callosotomy are those in whom language and motor dominance are controlled by different hemispheres; in left-handed persons, for example, the left side of the brain controls language, but the right side of the brain controls movement. Some of the problems resulting from callosotomy are caused by injury to the frontal lobes during the operation. Since the corpus callosum is buried deep between the frontal lobes, the middle portions of these lobes must be separated, which poses some risk. Surgical advances may help to minimize this risk.
Seizure frequency is reduced by an average of 70% to 80% after partial callosotomy and 80% to 90% after complete callosotomy. Partial seizures are often unchanged, but they may be improved or worsened. In many cases, especially after partial callosotomy, seizures are less frequent but persist.