Objective: To assess intellectual functioning (IQ) in 54 children and adolescents with intractable epilepsy who later underwent cortical resection due to unilateral malformations of cortical development acquired in utero.
Methods: Lesion type was classified into circumscribed mass lesions and diffuse cortical dysplasia based on histopathologic analysis of surgical tissue. Cortical dysplastic lesions were further graded as mild, moderate, or severe according to specific microscopic features. Laterality of lesion was determined through neurologic examination and electrophysiologic and neuroradiologic procedures. Classification of lesion type was corroborated by its significant relationship with other disease-related variables known to be related to clinical severity (age at seizure onset, age at resection, and extent of lesion).
Results: Analyses of covariance revealed that circumscribed lesions had a less deleterious effect on nonverbal IQ than did diffuse cortical dysplasia, after controlling for age at seizure onset and extent of lesion. This effect was also found on verbal IQ measures, but only in subjects with right-sided lesions. Subjects with left-sided lesions performed significantly more poorly on verbal IQ measures than those with right-sided lesions. Additionally, younger age at onset and greater extent of lesion were associated with poorer cognitive outcome.
Conclusions: Cortical dysplasia and early left hemisphere lesions have a significantly worse impact on cognitive functioning than circumscribed lesions or right hemisphere developmental lesions in children with epilepsy.