An MRI-Guided Robotic System to Improve Hippocampal Access for Epilepsy Interventions
Authors: John E. Peters, Abby M. Grillo, Mahshid Mansouri, Daniel S. Esser, Sarah Garrow, Nithin S. Kumar, Dario J. Englot, Joseph S. Neimat, William A. Grissom, Robert J. Webster, Eric J. Barth
Organizations: Department of Mechanical Engineering, Vanderbilt University, Nashville, TN, USA. · Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA. · Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, TN, USA. · Department of Neurological Surgery, University of Louisville Health, Louisville, KY, USA.
This paper presents an MRI-guided robotic system that improves hippocampal access by delivering a curved needle-like laser ablator through the foramen ovale, a natural opening in the base of the skull. Both the delivery path and the curved nature of the needle improve upon current clinical straight-line laser interstitial thermal therapy (LITT) as measured by hippocampal cannulation percentage. We describe the design of the robotic system which includes positioning, aiming, and curved needle deployment stages, followed by experimental results assessing cannulation percentages using MRI images in phantoms. In three curvilinear, single-insertion experiments, we achieved cannulation percentages of 93.5%, 96.5%, and 60.4%, exceeding reported clinical averages of 50-60%. Seizure control is believed by physicians to be a function of hippocampal volume treated, and our system provides a means of treating a greater volume of the hippocampus with LITT-based interventions.
Figures & tables
Figure 1: Transforaminal ablation approach in a patient skull. (A) Concentric docking tube, precurved tube, and laser fiber traversed through the foramen ovale and hippocampus. (B) Percutaneous approach of the docking tube to the foramen ovale.
Figure 2: Complete CAD rendering of the entire robotic system depicted for use in the scanner bore with a patient positioned for a percutaneous, transforaminal approach.
Figure 3: The actuation unit of the concentric tube robot from different perspectives. (A) Side view (docking tube hidden for simplicity) detailing the tubes, encoders, and fiber actuator. (B) Isometric view illustrating the concentric tubes, each capable of translation and rotation, as well as the precurved tube actuator. Docking tube is rigidly fixed to the CTAU housing. Inset shows the degrees of freedom (T: translation, R: rotation) associated with the fiber (red) and precurved tube (blue).
Figure 4: Detailed view of the robot’s 3D-printed, pneumatic, stepper actuators. (A) Isometric view of the precurved tube actuator (cyan) highlighting the translational DOF (pink arrow) including a linear gripper (grey) and its deflection (yellow arrows). (B) Rear view of the precurved tube actuator detailing the rotational DOF (red arrows) including a rotary gripper (grey) and its deflection (yellow arrows), a pair of rotary bellows and their deflection (green arrows), and various air inlets. (C) Rear view of the RPA actuator (cyan) detailing the rotational DOF (red arrows) including a rotary gripper (grey) and its deflection (yellow arrows), a pair of rotary bellows and their deflection (green arrows), and various air inlets. Each RPA actuator includes a second gripper (not shown) positioned on the opposing end of a common driveshaft. All actuators operate in a stepwise fashion executing either a translational or rotational step using alternating gripper states. Additional detail on the stepwise operation can be found in Peters et al. (2023) .
Figure 5: (A) Robotic Parallelogram Arm (RPA) used to adjust the angle of the initial entry vector of the docking tube. The body of each actuator (shown in Fig. 4 C) is affixed perpendicular to its axis of rotation in order to generate rotation in both the pitch and yaw directions. (B) A 6-DOF manual positioning platform aligns the RCM of the RPA to the foramen ovale.
Figure 6: Experimental setup with the assembled robotic system. (A) Robotic hardware for optical tracker experiments. (B) Robotic system inside the MRI scanner.
Figure 7: Free-space targeting results for four desired trajectories. The final tip errors were 1.70 mm, 1.75 mm, 1.18 mm, and 2.47 mm for Trials 1-4, respectively.
Figure 8: MRI‑guided phantom evaluation of the curved, transforaminal approach (n=3). For each trial, four spatial performance metrics are plotted versus arc length along the hippocampal medial axis (s = 0 at the head, increasing toward the tail; total length ≈ 40 mm). Corresponding 3D renderings depict the segmented hippocampus (semi‑transparent blue), its medial axis (dark blue), the planned trajectory (green), and the actual trajectory (magenta). Pale green shading marks the percent of the hippocampus cannulated by the actual path.
Performance Metric
Trial
Percent of Hippocampus Cannulated (%)
Plan Error (mm)
Tracking Error (mm)
Medial Axis Placement Error (mm)
Mean
Max
Mean
Max
Mean
Max
1
93.5
1.91
4.19
2.90
4.85
2.28
4.81
2
96.5
1.67
5.04
2.64
5.43
1.95
5.16
3
60.4
1.83
4.95
2.79
5.73
2.31
4.01
Mean
83.5
1.80
4.73
2.78
5.34
2.18
4.66
Table 1: Performance Metrics along the Hippocampal Arc Length for MRI-Guided Targeting Experiments
Predicting post-surgical seizure outcomes in pharmacoresistant epilepsy is a clinical challenge. Conventional deep-learning approaches operate on static, single-timepoint pre-operative scans, omitting longitudinal morphological changes. We propose Neuro-Oracle, a three-stage framework that: (i) distils pre-to-post-operative MRI changes into a compact 512-dimensional trajectory vector using a 3D Siamese contrastive encoder; (ii) retrieves historically similar surgical trajectories from a population archive via nearest-neighbour search; and (iii) synthesises a natural-language prognosis grounded in the retrieved evidence using a quantized Llama-3-8B reasoning agent. Evaluations are conducted on the public EPISURG dataset (N=268 longitudinally paired cases) using five-fold stratified cross-validation. Since ground-truth seizure-freedom scores are unavailable, we utilize a clinical proxy label based on the resection type. We acknowledge that the network representations may potentially learn the anatomical features of the resection cavities (i.e., temporal versus non-temporal locations) rather than true prognostic morphometry. Our current evaluation thus serves mainly as a proof-of-concept for the trajectory-aware retrieval architecture. Trajectory-based classifiers achieve AUC values between 0.834 and 0.905, compared with 0.793 for a single-timepoint ResNet-50 baseline. The Neuro-Oracle agent (M5) matches the AUC of purely discriminative trajectory classifiers (0.867) while producing structured justifications with zero observed hallucinations under our audit protocol. A Siamese Diversity Ensemble (M6) of trajectory-space classifiers attains an AUC of 0.905 without language-model overhead.
Safe navigation within the spinal subarachnoid space is constrained by its narrow, compliant, and delicate anatomy. Conventional catheters and continuum robots rely on proximal pushing, generating friction and shear along the tissue device interface that limit distal controllability and increase the risk of neural injury. Here, we present a 2 mm diameter eversion-growing robotic platform that enables friction minimised extension and steering within the human spinal subarachnoid space, validated through computational modelling, phantom experiments, and intact human cadaver studies. The robot integrates a miniature endoscope for real time intrathecal visualisation and advances by pressure driven tip eversion, localising motion to the distal tip while minimising translational sliding of the deployed body. Phantom experiments demonstrated reductions of 65.2% in mean interaction force and 48.0% in peak interaction force compared with matched push-based insertion. Physics based modelling showed that eversion based growth redistributed tissue loading, reducing local stress concentrations and interfacial shear relative to conventional insertion. In an intact human cadaver, the system achieved 150 mm of controlled intrathecal extension with concurrent fluoroscopic and endoscopic visualisation, providing access across multiple vertebral levels from a standard lumbar entry point. Postprocedural laminectomy and durotomy revealed no observable macroscopic disruption of the dura mater or surrounding neural structures. These results provide the first mechanically characterised and multimodally validated demonstration of eversion-based robotic navigation in intact human spinal anatomy, establishing a quantitative and procedural foundation for future intrathecal interventions. Further validation in larger anatomical cohorts and under physiological conditions will be required before clinical translation.
Zicong Wu, Panagiotis Kalozoumis, S. M. Hadi Sadati +8
Department of Surgical & Interventional Engineering, School of Biomedical Engineering & Imaging Sciences, Faculty of Life Sciences & Medicine, King’s College London, London WC2R 2LS, United Kingdom · Department of Computer Science & Biomedical Informatics, University of Thessaly, Lamia 35131, Greece · School of Engineering and Materials Science, Queen Mary University London, London E1 4NS, United Kingdom +2
Computational models of epilepsy promise patient-specific treatment design, but most optimization workflows still search for parameters that perform well on average. In neuromodulation, this is a weak target: a protocol that improves the mean response can still fail in the patient whose network is least tolerant to stimulation. We present a literature-guided minimax pipeline that couples PubMed-scale hypothesis extraction, The Virtual Brain (TVB) Epileptor simulations, and large-language-model-guided black-box optimization. The optimizer proposes either intrinsic model-control parameters or clinically interpretable external-stimulation protocols; TVB evaluates each proposal across sampled virtual patients; and the objective maximizes worst-case reward, defined as the negative variance of simulated seizure activity. In the intrinsic model-control experiment, the best archived parameter set improved worst-case reward from -0.5285 to -0.3182, a 39.8% gain over baseline. The clinical-style external-stimulation search produced a much smaller worst-case improvement (1.7%), and a 20-patient virtual cohort showed no aggregate benefit (p=0.9019), despite a 55% responder rate and a positive temporal-lobe subgroup signal. The study should be read as an in silico proof of concept for robust, literature-aware neurostimulation design, not as clinical evidence.