Neural representation and function of language in children with new onset partial epilepsy

Partial epilepsy is associated with the presence of atypical language representation and a higher incidence of language impairment. The relationship between these variables has not been studied at disease onset; thus, it is not known whether seizures drive these changes or if they are present before disease onset. Use of functional magnetic resonance imaging (fMRI) allows the study of patients early in the disease course, an option that was not available with the intracarotid sodium amobarbital procedure. We used blood oxygen dependent fMRI at 1.5 Tesla to assess language networks in 5 pediatric patients with new onset partial epilepsy of the left hemisphere and 23 normally developing children using an auditory semantic decision task. Nine patients and 23 normal volunteers completed a range of standardized cognitive and language measures. Group analysis of the volunteer data revealed a strongly left-lateralized pattern that closely resembles patterns typically observed in healthy adults. However, the magnitude and extent of activation in the fusiform gyrus suggest that children may be utilizing a developmental strategy, imagery, to complete the task. Measures of intersubject variability within language cortex captured a widespread network that suggests greater variability among a child population as compared to adults. Task performance was positively related to magnitude of signal change in the left middle frontal gyrus (BA 9). A region of interest analysis captured strongly left-lateralized regional indices among 4 of the patients and atypical, bilateral representation in 1 left-handed patient. The patient group performed more poorly on language measures than the control group suggesting that these skills may be compromised early in the disease course. Given the minimal seizure history and absence of structural lesions among these patients, these findings suggest that there may be an underlying disorder that manifests in epilepsy and its associated impairments.