てんかん外科におけるＯｐｔｉｃ Ｔｒａｃｔｏｇｒａｐｈｙの役割

Abstract

Diffusion tensor tractography is a newly developed method for tracing tracts in white matter using combination of diffusion tensor images. We evaluate the degree of impairment of optic tracts in the cases with visual field defect after temporal lobectomy using diffusion tensor tractography. We examined 8 cases after temporal lobectomy for temporal lobe epilepsy. Visual field defect in medial sector and lateral sector of upper 1/4 visual field were evaluated. Diffusion tensor tractography of optic radiation was made from 6 axes diffusion tensor images. We evaluated the correlation between the degree of visual field defect and visualization of Meyer's loop on tractographies. Medial sector field tends to be impaired after temporallobectomy. Diffusion tensor tractography showed incomplete to no visualization of Meyer's loop in the cases with severe visual field defect. While, visualization of optic radiation was almost complete in cases with mild visual field defect. Diffusion tensor tractography was useful in evaluating post surgical changes in optic radiation. Potential usefulness of tractography in surgical planning was also suggested.