Abstracts

Rationale: The purpose of this study was to determine the cortical origin of corticospinal tract (CST) and its location in the posterior limb of internal capsule (PLIC) using DTI tractography and to compare the CST origin with cortical stimulation data. Methods: This study included 32 children with intractable focal epilepsy (age: 2.2-17.6 yrs; 17 girls), who underwent DTI and functional motor mapping for the primary motor hand area using cortical stimulation. 23 healthy children (age: 2.5-12.4 yrs; 11 girls) also underwent DTI. The CST was delineated by DTI tractography, without presuming precentral gyrus to be the motor cortex: Regions of interest were placed at the anterior portion of the brainstem and at the corona radiata, and the cortical origin as well as its location in the PLIC was determined. In epileptic children, the cortical origin of CST in the affected hemisphere was compared to the location of primary motor hand areas determined by cortical stimulation. Subsequently, the origin of CST and its location in the PLIC in the affected hemisphere of the epileptic children was compared with those in the contralateral hemisphere as well as in controls. Results: In the affected hemisphere of epileptic children, DTI showed that the CST originated from the precentral gyrus in 3 children, from the postcentral gyrus in 4, and from both pre & postcentral gyri in 24 children. Cortical stimulation identified the primary motor hand area in the precentral gyrus in 1 epileptic child, in the postcentral gyrus in 5, and in both pre & postcentral gyri in 23 children. The proportion of overall agreement between cortical stimulation and DTI tractography in localization of motor cortex was 0.86, and positive agreement between these two modalities was found to be 0.92. The pattern of cortical origin of CST was similar between the affected and contralateral hemispheres of epileptic children as well as between epileptic children and controls (Table). In both affected and contralateral hemispheres of the epileptic children and in controls, the CST was located at around two-thirds of the way across from the anterior margin of the PLIC, and occupied about 25% of its dimension. Conclusions: We conclude that the CST frequently originates from both pre and postcentral gyri and is located at the posterior aspect of the PLIC. Furthermore, there is good concordance between DTI tractography and direct cortical stimulation in localization of the primary motor cortex; thus, DTI can be useful in non-invasive localization of CST.