White Matter Changes Along the Electrode Lead in Patients Treated With Deep Brain Stimulation

Effect of Anisotropic Brain Conductivity on Patient-Specific Volume of Tissue Activation in Deep Brain Stimulation for Parkinson Disease

OBJECTIVE

Deep brain stimulation (DBS) modeling can improve surgical targeting by quantifying the spatial extent of stimulation relative to subcortical structures of interest. A certain degree of model complexity is required to obtain accurate predictions, particularly complexity regarding electrical properties of the tissue around DBS electrodes. In this study, the effect of anisotropy on the volume of tissue activation (VTA) was evaluated in an individualized manner.

METHODS

Tissue activation models incorporating patient-specific tissue conductivity were built for 40 Parkinson disease patients who had received bilateral subthalamic nucleus (STN) DBS. To assess the impact of local changes in tissue anisotropy, one VTA was computed at each electrode contact using identical stimulation parameters. For comparison, VTAs were also computed assuming isotropic tissue conductivity. Stimulation location was considered by classifying the anisotropic VTAs relative to the STN. VTAs were characterized based on volume, spread in three directions, sphericity, and Dice coefficient.

RESULTS

Incorporating anisotropy generated significantly larger and less spherical VTAs overall. However, its effect on VTA size and shape was variable and more nuanced at the individual patient and implantation levels. Dorsal VTAs had significantly higher sphericity than ventral VTAs, suggesting more isotropic behavior. Contrastingly, lateral and posterior VTAs had significantly larger and smaller lateral-medial spreads, respectively. Volume and spread correlated negatively with sphericity.

CONCLUSION

The influence of anisotropy on VTA predictions is important to consider, and varies across patients and stimulation location.

SIGNIFICANCE

This study highlights the importance of considering individualized factors in DBS modeling to accurately characterize the VTA.

The white matter hyperintensities within the cholinergic pathways and cognitive performance in patients with Parkinson's disease after bilateral STN DBS

BACKGROUND

White matter hyperintensities (WMHs) in the cholinergic pathways are associated with cognitive impairment in Parkinson's disease (PD). This study aimed to investigate the role of WMHs within the cholinergic pathways in cognitive performance following bilateral subthalamic nucleus deep brain stimulation (STN DBS) in patients with PD.

METHODS

38 patients with PD who underwent bilateral STN DBS were assessed using the Cholinergic Pathways Hyperintensities Scale (CHIPS) with magnetic resonance imaging before surgery. Their cognitive statuses were evaluated pre-surgically and 6 months, 1 year, and 2 years post operation. The correlations between the CHIPS score and cognitive performance were analyzed. The differences in cognitive performance before and after the surgery between the high-CHIPS and low-CHIPS groups were also compared.

RESULTS

The CHIPS score in patients with PD negatively correlated with the general cognition assessed using Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) both at baseline and after DBS. No correlation was found between the CHIPS score and the change of MMSE and MoCA scores after DBS. No significant difference was observed in the change in cognitive performance after the surgery between the high and low-CHIPS groups.

CONCLUSION

The severity of cholinergic WMHs was correlated with the cognition in patients with PD both before and after the STN DBS. However, it does not correlate with the cognitive change in patients with PD after bilateral STN-DBS.

Image Guidance in Deep Brain Stimulation Surgery to Treat Parkinson's Disease: A Comprehensive Review

Deep brain stimulation (DBS) is an effective therapy as an alternative to pharmaceutical treatments for Parkinson's disease (PD). Aside from factors such as instrumentation, treatment plans, and surgical protocols, the success of the procedure depends heavily on the accurate placement of the electrode within the optimal therapeutic targets while avoiding vital structures that can cause surgical complications and adverse neurologic effects. Although specific surgical techniques for DBS can vary, interventional guidance with medical imaging has greatly contributed to the development, outcomes, and safety of the procedure. With rapid development in novel imaging techniques, computational methods, and surgical navigation software, as well as growing insights into the disease and mechanism of action of DBS, modern image guidance is expected to further enhance the capacity and efficacy of the procedure in treating PD. This article surveys the state-of-the-art techniques in image-guided DBS surgery to treat PD, and discusses their benefits and drawbacks, as well as future directions on the topic.