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Alexander G. Chartrain, Ahmed J. Awad, Jonathan J. Rasouli, Robert J. Rothrock and Brian H. Kopell

A 59-year-old woman with a 30-year history of essential tremor refractory to medical therapy underwent staged deep brain stimulation of the ventralis intermedius nucleus of the thalamus (VIM). Left-sided lead placement was performed first. Once in the operating room, microelectrode recording (MER) was performed to confirm the appropriate trajectory and identify the VIM border with the ventralis caudalis nucleus. MER was repeated after repositioning 2 mm anteriorly to reduce the likelihood of stimulation-induced paresthesias. Physical examination prior to permanent lead placement demonstrated micro-lesion effect, suggesting optimal trajectory. After implantation of the permanent lead, physical examination showed excellent results.

The video can be found here: https://youtu.be/nn3KRdmRCZ4.

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Alexey V. Dimov, Ajay Gupta, Brian H. Kopell and Yi Wang

OBJECTIVE

Faithful depiction of the subthalamic nucleus (STN) is critical for planning deep brain stimulation (DBS) surgery in patients with Parkinson’s disease (PD). Quantitative susceptibility mapping (QSM) has been shown to be superior to traditional T2-weighted spin echo imaging (T2w). The aim of the study was to describe submillimeter QSM for preoperative imaging of the STN in planning of DBS.

METHODS

Seven healthy volunteers were included in this study. T2w and QSM were obtained for all healthy volunteers, and images of different resolutions were reconstructed. Image quality and visibility of STN anatomical features were analyzed by a radiologist using a 5-point scale, and contrast properties of the STN and surrounding tissue were calculated. Additionally, data from 10 retrospectively and randomly selected PD patients who underwent 3-T MRI for DBS were analyzed for STN size and susceptibility gradient measurements.

RESULTS

Higher contrast-to-noise ratio (CNR) values were observed in both high-resolution and low-resolution QSM images. Inter-resolution comparison demonstrated improvement in CNR for QSM, but not for T2w images. QSM provided higher inter-quadrant contrast ratios (CR) within the STN, and depicted a gradient in the distribution of susceptibility sources not visible in T2w images.

CONCLUSIONS

For 3-T MRI, submillimeter QSM provides accurate delineation of the functional and anatomical STN features for DBS targeting.

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Alexey Dimov, Wahaj Patel, Yihao Yao, Yi Wang, Rafael O’Halloran and Brian H. Kopell

OBJECTIVE

The objective of this study was to investigate the relationship between iron and white matter connectivity in the subthalamic nucleus (STN) in patients undergoing deep brain stimulation (DBS) of the STN for treatment of Parkinson’s disease.

METHODS

Nine Parkinson’s disease patients underwent preoperative 3T MRI imaging which included acquisition of T1-weighted anatomical images along with diffusion tensor imaging (DTI) and quantitative susceptibility mapping (QSM). MR tractography was performed for the seed voxels located within the STN, and the correlations between normalized QSM values and the STN’s connectivity to a set of a priori chosen regions of interest were assessed.

RESULTS

A strong negative correlation was found between STN connectivity and QSM intensity for the thalamus, premotor, motor, and sensory regions, while a strong positive correlation was found for frontal, putamen, and brain stem areas.

CONCLUSIONS

Quantitative susceptibility mapping not only accurately delineates the STN borders but is also able to provide functional information about the STN functional subdivisions. The observed iron-to-connectivity correlation patterns may aid in planning DBS surgery to avoid unwanted side effects associated with DBS.