Impaired social cognition 30 years after hemispherectomy for intractable epilepsy: the importance of the right hemisphere in complex social functioning.

Clinical research with individuals following hemispherectomy typically quantifies the success of surgical outcomes by focusing primarily on the achievement of seizure control and the preservation of general brain functions, such as movement, sensation, language, and memory. In addition to these outcomes, careful study of individuals following hemispherectomy also has the potential to contribute to our understanding of functional brain asymmetries involving other complex cognitive behaviors. In this study, we report preliminary evidence for the lateralization of social perception. We administered a series of neuropsychological tests that were developed to assess emotional recognition and the formation of social inferences and advanced social cognitive judgments, as they occur in everyday situations, to two adult participants who underwent complete anatomic left- or right-sided hemispherectomy. Our results show that despite a 30-year postsurgical period of recovery and consistent and high levels of family support and social engagement, distinct cognitive profiles are still evident between our right- and left-sided participants. In particular, participant S.M., who underwent an anatomic right hemispherectomy, showed the most severe impairments in identifying negative emotional expressions and conversational exchanges involving lies and sarcasm and in "mentalizing" the intent of others. In contrast, participant J.H., who underwent an anatomic left hemispherectomy was highly skilled interpersonally, despite evident language-related limitations, and showed only mild difficulties when asked to identify emotional expressions involving disgust and anger. These results suggest that the right hemisphere plays a particularly important role in social cognitive functioning and reasoning. Further examination of the extent of social perceptual difficulties prior to and following surgical intervention for epilepsy may guide the development of effective social skills training programs that can improve quality of life beyond seizure control.