Cognitive and psychosocial deficits in agenesis of the corpus callosum with normal intelligence

Cognitive disabilities in agenesis of the corpus callosum (ACC) have been described in scattered reports, but few complete case descriptions are available. Consequent psychosocial disabilities in ACC have received little attention. We expected that ACC would be manifest in deficits specific to complex reasoning, concept formation, and problem solving. We also expected that these cognitive problems would be particularly evident in difficulties interpreting and understanding social situations, and in abnormal self-perception. Methods. Cognitive and psychosocial deficits were studied in two adolescents with ACC and normal IQ using a battery of cognitive and psychological tests. Results. Test results indicated poor interhemispheric integration of complex material. Performance on tests of reasoning, and concept formation were clearly below expectations based on IQ. Significantly poor performance was also found on tests of social insight, proverb interpretation, social logic, self-perception, and interpretation of ambiguous stimuli. Gross behavioural disorder or psychopathology were not found. Conclusions. ACC results in disabilities in social cognition that appear to be secondary to deficits in complex cognitive operations such as reasoning, concept formation, and problem solving. It is suggested that these cognitive deficits may be related to diminished interhemispheric transfer of complex information.