Diffusion tensor imaging tractography to visualize the relationship of the optic radiation to epileptogenic lesions prior to neurosurgery.
Bottom Line: However, in patients with lesions on or near the presumed course of the optic radiation, the potential benefits of resection must be balanced against the risk of a visual field deficit.The optic radiation shows significant anatomic variability, but can be reliably delineated by tractography.Future integration with real-time neuronavigation will minimize the risks of neurosurgery.
Affiliation: Epilepsy Society MRI Unit, Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, United Kingdom.Show MeSH
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Mentions: Fractional anisotropy and principal diffusion direction maps were used to identify the LGN by selecting the axial slice at the level of the transition from the posterior limb of the internal capsule to the cerebral peduncle. Voxels anterolateral to the LGN across the base of Meyer’s loop, with principal eigenvectors oriented in an anteromedial to posterolateral orientation, were identified and used to define a seed point in a coronal plane (Fig. 2A,C). Contiguous voxels, with principal directions in an anterior–posterior direction, were also selected in order to cover the entire coronal cross-section of Meyer’s loop, using a standardized seed point volume of 15 voxels (127 mm3). A second seed point was defined in the LGN on two axial slices (Fig. 2D) with a standardized volume of 18 voxels (152 mm3, 3 × 3 × 2 voxels) to ensure delineation of superior portion of the optic radiation. Data from these two seed regions were amalgamated to visualize the entire radiation.
Affiliation: Epilepsy Society MRI Unit, Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, United Kingdom.