Cognitive outcome of children with epilepsy and malformations of cortical development

Objective: To assess intellectual functioning (IQ) in 54 children and adole scents with intractable epilepsy who later underwent cortical resection due to unilateral malformations of cortical development acquired in utero. Met hods: Lesion type was classified into circumscribed mass lesions and diffus e cortical dysplasia based on histopathologic analysis of surgical tissue. Cortical dysplastic lesions were further graded as mild, moderate, or sever e according to specific microscopic features. Laterality of lesion was dete rmined through neurologic examination and electrophysiologic and neuroradio logic procedures. Classification of lesion type was corroborated by its sig nificant relationship with other disease-related variables known to be rela ted to clinical severity (age at seizure onset, age at resection, and exten t of lesion). Results: Analyses of covariance revealed that circumscribed l esions had a less deleterious effect on nonverbal IQ than did diffuse corti cal dysplasia, after controlling for age at seizure onset and extent of les ion. This effect was also found on verbal IQ measures, but only in subjects with right-sided lesions. Subjects with left-sided lesions performed signi ficantly more poorly on verbal IQ measures than those with right-sided lesi ons. Additionally, younger age at onset and greater extent of lesion were a ssociated with poorer cognitive outcome. Conclusions: Cortical dysplasia an d early left hemisphere lesions have a significantly worse impact on cognit ive functioning than circumscribed lesions or right hemisphere developmenta l lesions in children with epilepsy.