FIGURE 1. Homonymous hemianopsia after LITT for TLE FIGURE 1. Homonymous hemianopsia after LITT for TLE. A, Visual fields measured by an ophthalmologist at 2 weeks and 5 months postop showing improvement of visual function in the central right superior quadrant. B, Intraoperative sagittal IDZ image from the Visualase planning system (Medtronic Inc.). The white arrow highlights damage to the inferior thalamus. C, Sagittal, coronal, and axial contrasted T1 MRI sequences, respectively, with 2 mm cuts obtained at end of procedure, prior to removal of the laser catheter. The top of the laser catheter is slightly over 1 mm from the superior border of the hippocampal body. Contrast enhancement is seen extending into the inferior-most region of the thalamus (white arrow), the portion closest to the laser catheter. D, Sagittal, coronal, and axial 1 mm thin-cut MP-RAGE sequences at 2 months postop showing damage to the inferolateral thalamus at the level of the hippocampal body. E, Predicted location of LGN as determined from a 7T population statistical map (blue line) and laser trajectory (yellow line) merged onto 3T sagittal, coronal, and axial 1 mm thin-cut MP-RAGE images obtained at 5 months postop. The trajectory is not seen in the axial image because it is taken at the level of the LGN, superior to the trajectory. Scale bar for B-D: 0.5 cm. A, anterior; L, lateral; M, medial; S, superior. From: Visual Deficit From Laser Interstitial Thermal Therapy for Temporal Lobe Epilepsy: Anatomical Considerations Oper Neurosurg (Hagerstown). 2017;13(5):627-633. doi:10.1093/ons/opx029 Oper Neurosurg (Hagerstown) | Copyright © 2017 by the Congress of Neurological Surgeons

FIGURE 2. DTI tractography of optic radiations FIGURE 2. DTI tractography of optic radiations. A, Projection of fibers from thalamus to visual cortex in the axial plane for the patient with the postop visual deficit, showing reduced fiber density ipsilateral to the hippocampal ablation (left side, yellow tracts highlighted by black arrow) compared to the contralateral hemisphere (red tracts). B and C, Sagittal representations of distal optic radiation fibers at the level of the calcarine fissure contralateral and ipsilateral to the hippocampal ablation, respectively. D, Three-dimensional rendering of optic radiation fibers ipsilateral (yellow) and contralateral (red) to the ablation from a superior-left perspective. E, Three-dimensional rendering of the same fibers from a superior-right perspective. White bar: 1.0 cm. A, anterior; L, lateral; P, posterior; S, superior. From: Visual Deficit From Laser Interstitial Thermal Therapy for Temporal Lobe Epilepsy: Anatomical Considerations Oper Neurosurg (Hagerstown). 2017;13(5):627-633. doi:10.1093/ons/opx029 Oper Neurosurg (Hagerstown) | Copyright © 2017 by the Congress of Neurological Surgeons

FIGURE 3. Craniocaudal location of laser catheter at hippocampal body FIGURE 3. Craniocaudal location of laser catheter at hippocampal body. A, Scatter plot showing relative location of all 18 patients’ laser catheters along the craniocaudal axis, as determined from coronal intra-op contrasted T1 images. The red dot represents the patient with the homonymous hemianopsia. Medial, right. The sagittal image above shows the anteroposterior position at which laser location was typically measured, indicated by the yellow line. This position along the hippocampal formation was typically where the laser catheter came in closest proximity to the superior border of the hippocampus. Anterior, left. Scale bar: 1.0 cm. B, Frequency histogram created by integrating horizontally over the scatter plot from (A). The y-axis shows craniocaudal catheter location and x-axis shows patient number. The red horizontal arrow shows catheter location for the patient with the postop homonymous hemianopsia. CF, choroidal fissure; H, hippocampus; PHG, parahippocampal gyrus; WM, white matter tracts. From: Visual Deficit From Laser Interstitial Thermal Therapy for Temporal Lobe Epilepsy: Anatomical Considerations Oper Neurosurg (Hagerstown). 2017;13(5):627-633. doi:10.1093/ons/opx029 Oper Neurosurg (Hagerstown) | Copyright © 2017 by the Congress of Neurological Surgeons

FIGURE 4. Importance of choroidal fissure CSF volume in protecting LGN from thermal injury. The top row shows typical coronal MP-RAGE slices at the hippocampal body for representative patients with low A, middle B, and high C CSF volumes, as determined from manual tracings of preop images. The patient in (A) was the patient with the homonymous hemianopsia complication. Arrow bar: 0.5 cm. M, medial; S, superior. D-F, Volumetric renderings from an anterosuperior perspective of the hippocampus and CSF spaces above for the same low, mid, and high CSF volume patients. The yellow tracing in each rendering shows the estimated location of the thalamic ablation zone from the patient with the deficit, which was estimated by obtaining a rendering of his thalamic ablation relative to the hippocampus, and then laying this illustration over the renderings from the other patients using image processing software. The patient with the visual deficit A had visibly less CSF between the hippocampal body and LGN than the other patients. Red, hippocampus; blue, CSF; A, anterior; M, medial; P, posterior. G, Correlation of CSF volume superior to hippocampus with hippocampal volume. H, Correlation of the same CSF volumes with patient age. I, Correlation of the percent of pixels in each patient classified as CSF by pixel intensity with the volume of CSF traced superior to the hippocampus. From: Visual Deficit From Laser Interstitial Thermal Therapy for Temporal Lobe Epilepsy: Anatomical Considerations Oper Neurosurg (Hagerstown). 2017;13(5):627-633. doi:10.1093/ons/opx029 Oper Neurosurg (Hagerstown) | Copyright © 2017 by the Congress of Neurological Surgeons

FIGURE 5. Location and retinotopic organization of LGN FIGURE 5. Location and retinotopic organization of LGN. A, Diagram of sagittal view of hippocampal formation. The LGN is typically located at the inferior-most aspect of the thalamus and is situated closer to the laser during a typical trajectory (gray dotted line) than any other thalamic nucleus. Given the curvilinear shape of the hippocampus, this is also the location of the hippocampus where the laser comes into closes proximity to the superior hippocampal border. The black arrow shows the anteroposterior location of the cross-section shown in B. B, Diagram of a typical coronal view through the hippocampal body showing the typical location of the LGN relative to the hippocampus. The 3 different shades of the LGN show the retinotopic organization of the nucleus, with dark gray representing foveal vision and white representing peripheral vision. C, Visual field map with shades of gray showing the visual representations corresponding to the retinotopic LGN regions highlighted in B. A, amygdala; AC, ambient cistern; CF, choroidal fissure; H, hippocampus; V, lateral ventricle; WM, white matter tracts; M, medial; P, posterior; S, superior. From: Visual Deficit From Laser Interstitial Thermal Therapy for Temporal Lobe Epilepsy: Anatomical Considerations Oper Neurosurg (Hagerstown). 2017;13(5):627-633. doi:10.1093/ons/opx029 Oper Neurosurg (Hagerstown) | Copyright © 2017 by the Congress of Neurological Surgeons