Tractography-Guided Stimulation of Somatosensory Fibers for Thalamic Pain Relief

Abstract

Background: The spinothalamocortical tract (STC) is seen as a neural tract responsible for or involved in the generation or transmission of thalamic pain. Either the thalamus itself or the posterior limb of the internal capsule (PLIC) are targets for deep brain stimulation (DBS) in patients with thalamic pain, but due to its low contrast, conventional MRI cannot visualize the STC directly. Objectives: To show the feasibility of integrating diffusion tensor imaging-based tractography into the stereotactic treatment planning for identification of an object-oriented lead trajectory that allows STC-DBS with multiple electrode contacts. Methods: Diffusion tensor imaging was performed in 4 patients with thalamic pain. The STC was modeled and integrated into the stereotactic treatment planning for DBS. DBS-lead implantation was done according to trajectory planning along the modeled STC at the level of the PLIC. Results: After implantation, electrode stimulation was possible over a length of more than 20 mm with a tractography-based trajectory along the PLIC part of the STC. After a follow-up of 12 months, pain relief of more than 40% was achieved in 3 of 4 patients with rating on a visual analogue scale. In 1 patient, stimulation failed to reach any long-lasting positive effects. Conclusions: Integrating tractography data into stereotactic planning of DBS in thalamic pain is technically feasible. It can be used to identify a lead trajectory that allows for multiple contact stimulation along the STC at the level of the PLIC. Due to long-lasting positive stimulation effect, tractography-guided stimulation of sensory fibers seems to be beneficial for thalamic pain relief.

Integrating Diffusion Tensor Imaging-Based Tractography into Deep Brain Stimulation Surgery: A Review of the Literature

“…Another group of researchers [51] used deterministic tractography for the planning of DBS of the spinothalamic tract, which, due to its low contrast, cannot be visualized with conventional MRI. They performed DTI in 4 patients with thalamic pain, at the level of the posterolateral internal capsule.…”

“…Tractography helped to choose a target region in such a way that the DBS electrode covered, at a length of over 20 mm, the sensory fiber from the target in the direction of the entry point. At the 12-month follow-up, a pain relief of more than 40% by rating on a visual pain scale was achieved in 3 of the 4 patients [51]. …”

Diffusion Tensor Imaging-Based Thalamic Segmentation in Deep Brain Stimulation for Chronic Pain Conditions

“…The reliable placement of leads in the VPL/VPM nuclei based on individualized thalamic anatomy could allow for implantation without clinical neurophysiological assessment or microelectrode recordings, shortening operative times and eliminating patient discomfort associated with wakefulness during the procedure. Furthermore, directly visualizing the DTI-determined sensory thalamus to guide initial targeting may minimize electrode passes, reducing the risk of hemorrhage [32,33]. Finally, by evaluating each electrode in relation to its vicinity to the sensory thalamic fibers, one can potentially use these patient-specific maps to guide programming and patient management.…”

The Promising Role of Neuromodulation in Improving Ischemic Stroke Recovery

“…The role of imagingbased tractography in the stereotactic trajectory planning for the placement of a spinothalamocortical tract (STC) DBS in thalamic pain has the potential to literally color the field currently obscured by limitations of low contrast in MR imaging of the posterior limb of the internal capsule or thalamus, targets for DBS. A study examining this technology yielded results demonstrating a reduction in pain by 40% in 75% of patients studied, lasting for greater than one year [47]. While invasive neuromodulation my hold a role in pain management post-stroke, studies also affirm the role of non-invasive treatments in cases of stroke-induced thalamic pain syndromes via gamma knife radiosurgery of the centromedian nucleus, resulting in improved symptom control and quality of life [48].…”