Malformations of cortical development: high-resolution MR and diffusion tensor imaging of fiber tracts at 3T

Abstract

Patients with malformations of cortical development and epilepsy may have a variety of abnormal brain findings, including abnormal gyral patterns, cortical thickening, decreased volume of white matter, and increased diffusion of white matter. The status of individual white matter fiber tracts, however, is unknown. We present a case of bilateral frontal schizencephaly and subcortical heterotopia and illustrate alterations of white matter fascicles by combined structural and functional diffusion tensor imaging at 3 T.

Fig 1.

Conventional MR images obtained at 1.5 T and 3 T. A, Axial T1-weighted image obtained at 1.5 T shows bilateral closed lip schizencephaly (arrow and arrowheads) and absent septum pellucidum. B, Coronal image obtained at 3T through the schizencephalic cleft reveals individual linear radiations of gray matter signal (arrowheads) extending from the cortex to the ventricle.

Fig 2.

Principal eigenvector maps obtained from diffusion tensor imaging. A, Axial color map corresponding to the main direction of the white matter fiber orientation: by convention, blue indicates fibers (e.g., corona radiata) running in the superior to inferior direction, green indicates anterior to posterior (e.g., superior longitudinal fasciculus), and red indicates right-left fibers (e.g., corpus callosum). In our patient, the white matter fibers show deviation in the main direction of the diffusion tensor around the abnormal gray matter of the schizencephalic cleft (asterisk). B, In a healthy individual, the cingulum (arrow) is a long thin fascicle, lying immediately superior to the corpus callosum, oriented in an anterioposterior direction. C, The cingulum in our patient (arrow) is shortened and distorted. Note also thinning of the corpus callosum (red) below the cingulum.

Fig 3.

Fiber tract reconstruction images. A, 2D projections of fiber tract reconstruction superimposed on sagittal fractional anisotropy map showing the deep schizencephaly (asterisk) separating the corticospinal tract (arrow) from other fibers. B, In our patient, the superior longitudinal fasciculus is poorly developed and deviated by the schizencephalic cleft (asterisk). C, Only a few thin fibers are seen in the in the body of the corpus callosum, and the fibers in the splenium (arrow) are oriented in complex directions.