MRI ANATOMY OF WHITE-MATTER LAYERS AROUND THE TRIGONE OF THE LATERAL VENTRICLE

MRI was obtained in eight normal volunteers and seven patients with br ain oedema around the trigone. In addition to the conventional sequenc es, diffusion-weighted and intravoxel-incoherent-motion images using m otion-proving anteroposterior and/or lateral direction gradients were obtained to show the white matter pathways better. Coronal proton-dens ity-weighted images showed three thin relatively high-intensity layers in addition to the tapetum and the internal and external sagittal str ata. Although they have not been confirmed anatomically, the thin laye r between the internal and the external sagittal strata was corroborat ed by diffusion-weighted and intravoxel-incoherent-motion images, and by characteristics of the spread of oedema into the sagittal stratum. We propose that this layer be named the central sagittal lamina. The o ther two layers medial and lateral to the sagittal stratum were outsid e, but in contact with the medial and lateral parts of the sagittal st ratum, respectively. We provisionally named them medial and lateral sa gittal laminae; they mere not evident on any other images. The low-int ensity layer on T2-weighting was the internal sagittal stratum. The op tic radiation, comprising the external sagittal stratum, appeared as a n intermediate to slightly high-intensity layer on T2-weighted images and a low-intensity layer on T1-weighted images as did the corticospin al tract in the posterior internal capsule.