Authors :
Presenting Author: Fidelia Gaba, BS – University of Pittsburgh School of Medicine
Jasmine Hect, BS – Children’s Hospital of Pittsburgh, University of Pittsburgh Medical Center; Emily Harford, MA – Children’s Hospital of Pittsburgh, University of Pittsburgh Medical Center; Frank Yeh, MD, PhD – Department of Neurosurgery, University of Pittsburgh Medical Center; Jessica Barrios- Martinez, MD – Department of Neurosurgery, University of Pittsburgh Medical Center; Taylor Abel, MD – Department of Neurosurgery, University of Pittsburgh Medical Center
Rationale:
Corpus callosotomy (CC) is the standard surgical intervention for palliation of atonic seizures for patients with drug-resistant epilepsy (Asadi-Pooya et al., 2018). Minimally invasive techniques have been developed as an alternative to CC, which requires a craniotomy. MRI-guided laser interstitial thermal therapy (MRgLITT) is a promising alternative to achieve disconnection viacorpus callosum ablation (CCA). While institutional series suggest that MRgLITT CCA is safe, effective, and requires shorter hospitalization, a lower extent of disconnection is a perceived drawback of this approach (Caruso et al., 2021; Badger et al., 2020).
Anatomical MR-imaging (T1 or T2 weighted) after MRgLITT CCA is acquired to assess post-operative changes within the ablated tissues and ascertain extent of disconnection (Mallela et al. 2022). However, anatomical imaging may be insufficient to completely capture residual connectivity. Tractography imaging modalities, such as Diffusion Tensor Imaging (DTI) and High-Density Fiber Tractography (HDFT), measure white matter connectivity through the measurement of water diffusion through tissues in vivo (Abhinav et al., 2015). Differential tractography compares imaging scans to another and maps differences longitudinally to measure changes post-operatively or capture disease progression (Yeh et al., 2019).
We hypothesize that tractography, measured with HDFT, can provide more information about changes in interhemispheric connectivity post MRgLITT CCA than anatomical imaging alone.
Methods:
The study cohort consists of pediatric patients with drug-resistant epilepsy who underwent MgLITT as a palliative treatment for atonic seizures. At 3-month follow-up patients underwent High Density Fiber Tractography (HDFT) as part of routine clinical imaging.
DSI studios is used to field correct postoperative images and reconstruct the diffusion data using a generalized q-sampling imaging (GQI) approach. GQI is a model-free method for resolving fiber orientations and quantifying the anisotropy of diffusing water. After reconstruction, differential tractography is applied to visualize longitudinal changes in callosal white matter and quantify large-scale changes in volume and fractional anisotropy. Postoperative imaging was compared against age- and sex-matched regressed HDFT imaging generated from the Human Connectome Project (HCP) Young Adult database.
Results:
Tractography improves localization of regions with complete corpus callosum ablation and regions with residual functional fibers. We found that most residual fibers were located in the tapetum and splenium, whereas complete ablation was consistently seen in the genu and body. Differential tractography indicates that most of the remaining fibers seen in the tapetum and splenium are still undergoing degenerative changes at three months postoperatively.
Conclusions:
Our study supports the hypothesis that the application of HDFT tractography offers more insights into changes in interhemispheric connectivity following MRgLITT CCA when compared to using anatomical imaging alone. This information can be applied to guide surgical decision making and assess the extent of disconnection following MRgLITT CCA.
Funding: None