John W Rutland1, Rebecca E Feldman2, Bradley N Delman3, Fedor Panov4, Madeline C Fields5, Lara V Marcuse5, Patrick R Hof6, Hung-Mo Lin7, Priti Balchandani2. 1. Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States; Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States. Electronic address: jack.rutland@mssm.edu. 2. Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States; Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States. 3. Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States. 4. Department of Neurosurgery, Mount Sinai Hospital, New York, NY, United States. 5. Department of Neurology, Mount Sinai Hospital, New York, NY, United States. 6. Department of Neuroscience, Mount Sinai Hospital, New York, NY, United States. 7. Department of Population Health Science and Policy, Mount Sinai Hospital, New York, NY, United States.
Abstract
PURPOSE: MRI-negative epilepsy patients could benefit from advanced imaging techniques such as high-resolution diffusion magnetic resonance imaging (dMRI). Our aim was to perform hippocampal subfield-specific tractography and quantify connectivity of the subfields in MRI-negative patients. Abnormal connectivity of the hippocampal subfields may help inform seizure focus hypothesis and provide information to guide surgical intervention. METHODS: Hippocampal structural imaging and dMRI was acquired in 25 drug resistant MRI-negative patients and 25 healthy volunteers. The hippocampi of each subject was segmented on high-resolution structural images and dMRI-based probabilistic tractography was performed in each subfield. The degrees of connectivity and fiber densities of the hippocampal subfields were quantified and compared between epilepsy patients and healthy volunteers. RESULTS: We were able to perform subfield-specific hippocampal tractography in each subject that participated in this study. These methods identified some hippocampal subfields that are abnormally connected in MRI-negative patients. In particular patients suspected of left temporal seizure focus exhibited increased connectivity of certain ipsilateral subfields, especially the subiculum, presubiculum, and parasubiculum, and reduced connectivity of some contralateral subfields, such as CA1 and subiculum. CONCLUSIONS: Our data suggest that the hippocampal subfields are connected in distinct ways in different types of epilepsy. These results may provide important information that could help inform seizure focus hypothesis and in the surgical treatment of MRI-negative patients. These observations suggest that high-resolution dMRI-based tractography of the hippocampal subfields can detect subtle abnormalities in otherwise normal-appearing MRI-negative patients.
PURPOSE: MRI-negative epilepsypatients could benefit from advanced imaging techniques such as high-resolution diffusion magnetic resonance imaging (dMRI). Our aim was to perform hippocampal subfield-specific tractography and quantify connectivity of the subfields in MRI-negative patients. Abnormal connectivity of the hippocampal subfields may help inform seizure focus hypothesis and provide information to guide surgical intervention. METHODS: Hippocampal structural imaging and dMRI was acquired in 25 drug resistant MRI-negative patients and 25 healthy volunteers. The hippocampi of each subject was segmented on high-resolution structural images and dMRI-based probabilistic tractography was performed in each subfield. The degrees of connectivity and fiber densities of the hippocampal subfields were quantified and compared between epilepsypatients and healthy volunteers. RESULTS: We were able to perform subfield-specific hippocampal tractography in each subject that participated in this study. These methods identified some hippocampal subfields that are abnormally connected in MRI-negative patients. In particular patients suspected of left temporal seizure focus exhibited increased connectivity of certain ipsilateral subfields, especially the subiculum, presubiculum, and parasubiculum, and reduced connectivity of some contralateral subfields, such as CA1 and subiculum. CONCLUSIONS: Our data suggest that the hippocampal subfields are connected in distinct ways in different types of epilepsy. These results may provide important information that could help inform seizure focus hypothesis and in the surgical treatment of MRI-negative patients. These observations suggest that high-resolution dMRI-based tractography of the hippocampal subfields can detect subtle abnormalities in otherwise normal-appearing MRI-negative patients.
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