Abstract
BackgroundVisual field defects caused by injury to Meyer’s loop (ML) are common in patients undergoing anterior temporal lobectomy during epilepsy surgery. Evaluation of the anatomical shapes of the curving, fanning and sharp angles of ML to guide surgeries is important but still challenging for diffusion tensor imaging. We present an advanced diffusion data-based ML atlas and labeling protocol to reproduce anatomical features in individuals within a short time.MethodsThirty Massachusetts General Hospital-Human Connectome Project (MGH-HCP) diffusion datasets (ultra-high magnetic gradient & 512 directions) were warped to standard space. The resulting fibers were projected together to create an atlas. The anatomical features and the tractography correspondence rates were evaluated in 30 MGH-HCP individuals and local diffusion spectrum imaging data (eight healthy subjects and six hippocampal sclerosis patients).ResultsIn the atlas, features of curves, sharp angles and fanning shapes were adequately reproduced. The distances from the anterior tip of the temporal lobe to the anterior ridge of Meyer’s loop were 23.1 mm and 26.41 mm on the left and right sides, respectively. The upper and lower divisions of the ML were revealed to be twisting. Eighty-eight labeled sides were achieved, and the correspondence rates were 87.44% ± 6.92, 80.81 ± 10.62 and 72.83% ± 14.03% for MGH-HCP individuals, DSI-healthy individuals and DSI-patients, respectively.ConclusionAtlas-labeled ML is comparable to high angular resolution tractography in healthy or hippocampal sclerosis patients. Therefore, rapid identification of the ML location with a single modality of T1 is practical. This protocol would facilitate functional studies and visual field protection during neurosurgery.
Highlights
Visual field defects caused by injury to Meyer’s loop (ML) are common in patients undergoing anterior temporal lobectomy during epilepsy surgery
Shan et al BMC Neurology (2019) 19:302 orientation for each voxel, it is challenging for diffusion tensor imaging (DTI) to decode direction from voxels that contain angular fibers (such as sharp angles between the optic tract (OT) and ML and the dramatic anterior extended curvature of fibers in the loop), fanning fibers (such as fanning fibers originating from the lateral geniculate nucleus (LGN)) and crossing fibers [15]; it cannot decode the anatomical features of the ML
The Upper branch of optic radiation (ORu) and Lower branch of optic radiation (ORl) were observed in a twisted arrangement (Fig. 2) in which the ORu started in a medial and superior position to the ORl; at the posterior portion of the optic radiation (OR), while still maintaining a superior position, the ORu became slightly lateral to the ORl
Summary
Visual field defects caused by injury to Meyer’s loop (ML) are common in patients undergoing anterior temporal lobectomy during epilepsy surgery. Previous studies have visualized ML using diffusion tensor imaging (DTI) to protect visual function [8,9,10,11,12,13,14]. As it decodes only the average trend of. A low estimation of the anterior extension of ML might exist This point was supported by previous studies in which the distance from the anterior tip of the temporal lobe to the anterior ridge of Meyer’s loop (dTM) was measured. Different approaches are still needed to facilitate the evaluation of the anterior extension of ML
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