Abstract

Objectives: To develop and evaluate a patient-specific, connectomic-guided approach for optimizing thalamic target selection in Gamma Knife radiosurgery for refractory pain, integrating individual thalamic anatomy and functional connectivity to enhance efficacy and safety compared to traditional indirect targeting methods.

Methods: We described the validation of the thalamic target through structural and functional connectivity of the thalamic target (Lovo, 2025). Using BrainLab Elements (BrainLab, Munich, Germany), a tractography study was performed at the VPM nucleus, and the fiber bundles from primary motor (M1) and sensory (S1) cortices crossing the VPM nucleus (Latera pain pathway). The same was done for the orbitofrontal medial region and the PVG (Descending pathway). The area in between the PVG and the VPM, M1, or superior frontal gyrus (SFG), marking the medial pathway, this later pathway was targeted, and coordinates were obtained.
A 3D reconstruction on a cefalocaudal (superior) view of all the pain pathways, the S1 is shown for reference, in the middle, the two circular images, one in green to the left and orange to the right, represent the target and an approximation of the 20 Gy isodose line.
The composite figure exemplifies the translation of the coordinates from Brainlab Elements in the orange box to the Gamma Plan. The prescription dose was 45 Gy to the 50%, with a 4 mm collimator shot bilaterally, the 20 Gy isodose line was considered to allow dose volume histogram information of the VPM and PVG, although the main target corresponds to the area of the Centromedian (CM) and Parafascicular complex (PFc). Also, the etiology of pain determined the combined target for the approach alongside the thalamus irradiation (Hypophysis or TN).

Results: In our patients, the mean initial VAS score during crises was 9.75 (range: 9–10), which decreased to 1.5 (range: 0–6) at the last follow-up. The mean time to achieve pain control was 2.1 months (range: 0.26–3). The mean follow-up duration was 3.75 months (range: 2–6). Patient 1, VAS scores in crises, initial: 9/10, Last follow-up at 5 months: 0/10. Patient 2, VAS scores in crises, initial: 10/10, last follow-up at 3 months: 6/10 without continuous
concomitant pain. Patient 3, VAS scores in crises: initial: 10/10, last follow-up at 2 months: 0/10. Patient 4, VAS scores: initial: 10/10, last follow-up: 0/10. No adverse effects were reported.

Conclusion(s): Connectomic-based medial thalamotomy seems to refine target selection to patient-specific anatomy, and also have proved to achieve substantial pain control regardless of the etiology, probably while implying the three main pain pathways (medial, lateral, and descendent) with the medial thalamus shot, while maintaining the safety, feasibility, and  effectiveness, as previously reported in other case series with indirect targeting. Connectomic-guided targeting was feasible by the incorporation of Brainlab Elements, allowing for a patient-specific radiosurgery strategy.