CORPUS CALLOSOTOMY - A QUANTITATIVE STUDY OF THE EXTENT OF RESECTION,SEIZURE CONTROL, AND NEUROPSYCHOLOGICAL OUTCOME

Corpus callosotomy is valuable for controlling medically intractable g eneralized seizures in appropriate patients, but postoperative develop ment of language disorders, neuropsychological impairment, and motor d ysfunction have all been noted. The extent of callosum resection has b een implicated as a possible determinant of outcome, but this hypothes is has not been formally tested. Analysis of the records of all patien ts who underwent corpus callosotomy at the University of California, S an Francisco, from 1986 to 1991 showed that, of 15 patients who underw ent anterior or complete callosotomy, seven were entirely or nearly se izure-free, four had at least a 50% reduction in seizure frequency, an d four had no change. To determine callosal size and extent of calloso tomy, preoperative and postoperative magnetic resonance images were me asured with computer-based planimetry. Seizure outcome was not signifi cantly associated with preoperative callosal size or extent of calloso tomy. Intelligence quotient scores did not change significantly after callosotomy. No severe neuropsychological deficits developed after ant erior or complete callosotomy, even in patients with mixed cerebral do minance or bilateral language representation. These results indicate t hat division of the anterior one-half to two-thirds of the corpus call osum is nearly as effective as more extensive anterior sectioning or c omplete callosotomy in reducing drop-attack and generalized tonic-clon ic seizures in appropriate patients, and that the extent of callosotom y is not an important factor on outcome when at least 50% to 65% of th e callosum is divided. Mixed cerebral dominance and other unusual patt erns of language and memory organization do not appear to increase the postoperative risk for neuropsychological deficits, regardless of the extent of anterior section.