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Neurosci Lett. 2014 May 7;568:56-61. doi: 10.1016/j.neulet.2014.03.049. Epub 2014 Mar 29.

Case report: practicability of functionally based tractography of the optic radiation during presurgical epilepsy work up.

Author information

1
Department of Neurology, Otto-von-Guericke University, Leipziger Str. 44, D-39120 Magdeburg, Germany. Electronic address: FC.Schmitt@med.ovgu.de.
2
Department of Neurology, Otto-von-Guericke University, Leipziger Str. 44, D-39120 Magdeburg, Germany.
3
Department of Ophthalmology, Otto-von-Guericke University, Leipziger Str. 44, D-39120 Magdeburg, Germany; Center for Behavioural Brain Science (CBBS), Otto-von-Guericke-University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
4
Department of Neurology, Otto-von-Guericke University, Leipziger Str. 44, D-39120 Magdeburg, Germany; Center for Behavioural Brain Science (CBBS), Otto-von-Guericke-University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
5
Epilepsy Center Erlangen, University of Erlangen-Nürnberg, Schwabachanlage 6, 91054 Erlangen, Germany.
6
Department of Stereotactic Neurosurgery, Otto-von-Guericke University, Leipziger Str. 44, D-39120 Magdeburg, Germany; Leibnitz Institute of Neurobiology, Leipziger Str. 44, D-39120 Magdeburg, Germany.
7
Department of Neurology, Otto-von-Guericke University, Leipziger Str. 44, D-39120 Magdeburg, Germany; Leibnitz Institute of Neurobiology, Leipziger Str. 44, D-39120 Magdeburg, Germany.
8
Department of Stereotactic Neurosurgery, Otto-von-Guericke University, Leipziger Str. 44, D-39120 Magdeburg, Germany.
9
Department of Neurology, Otto-von-Guericke University, Leipziger Str. 44, D-39120 Magdeburg, Germany; Department of Economics, University Zurich, Blümlisalpstrasse 10, CH-8006 Zurich, Switzerland.

Abstract

Pre-operative tractography of the optic radiation (OR) has been advised to assess the risk for postoperative visual field deficit (VFD) in certain candidates for resective epilepsy surgery. Diffusion tensor imaging (DTI) tractography relies on a precise anatomical determination of start and target regions of interest (ROIs), such as the lateral geniculate nucleus (LGN) and the primary visual cortex (V1). The post-chiasmal visual pathway and V1 show considerable inter-individual variability, and in epilepsy patients parenchymatous lesions might further complicate this matter. A functionally based tractography (FBT) seems beneficial for precise OR identification. We assessed practicability of FBT for OR identification in a patient with occipital lobe epilepsy due to a temporo-occipital maldevelopmental tumor. The MRI protocol at 3T included a T1-weighted sagittal 3D scan, a T2-weighted axial 2D scan and a DTI scan using an echo planar spin echo sequence. ROIs for fiber tracking of OR (LGN & V1) were determined with T2*-weighted fMRI-based retinotopic assessment. After DTI pre-processing and fiber tracking, paths with similar properties were combined in clusters for visual presentation and OR localization. Retinotopic phase maps allowed for the identification of V1 and LGN for a precise DTI-based reconstruction of OR, which was distant to the patient's tumor. Location and structure of ORs were comparable in each hemisphere. FBT could thus influence the human research of the extrastriate visual pathway and the risk management of post-operative VFD in epilepsy surgery.

KEYWORDS:

DTI; Lateral geniculate nucleus; Primary visual cortex; Retinotopy

PMID:
24690576
DOI:
10.1016/j.neulet.2014.03.049
[Indexed for MEDLINE]
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