Functional consequences of a section of the anterior part of the body of the corpus callosum: evidence from an interhemispheric transcallosal approach

The aim of this study was to determine the neuropsychological consequences of a middle interhemispheric approach for the removal of tumors of the third or lateral ventricles. A retrospective analysis of eight callosotomized patients for ventricular tumors (three males/five females; mean age: 48.7 +/- A 11.2 years; education level: 11.9 +/- A 2.9 years) and eight healthy subjects was performed. An extensive neuropsychological test battery was used to evaluate global intellectual efficiency, memory capacities, executive functions, and interhemispheric transfer of a procedural learning task (serial reaction time task/SRTT). Neuropsychological results showed that: (1) five of eight patients operated through a middle transcallosal approach had disturbances of verbal or visual memory; (2) three of eight patients displayed a dysexecutive cognitive syndrome (two of eight of whom presenting with a deficit of verbal fluency); (3) two of eight patients presented a dysexecutive behavior syndrome; and (4) with regard to the SRTT, although all participants learned the task, in contrast to controls, the callosotomized patients showed an increase in reaction times and an absence of interhemispheric transfer of learning from one hand to the other. The transcallosal approach transects a large number of callosal fibers. This damage accounts for the deficits of memory, the dysexecutive cognitive and behavioral syndrome, and disturbances in interhemispheric transfer of learning.