55. Ulusal Nöroloji Kongresi

NOROKONGRE 2019


 
THE EFFECT OF BRAİN ATROPHY ON POST-OPERATİVE DBS LEAD MİGRATİON: ELECTRODE DİSPLACEMENT AND PROXİMAL LEAD BOWİNG
MERVE TAN 1 RéMİ PATRİAT 2 NOAM HAREL 2

1- KOÇ ÜNİVERSİTESİ TIP FAKÜLTESİ
2- UNİVERSİTY OF MİNNESOTA, CENTER FOR MAGNETİC RESONANCE RESEARCH
 
Amaç:

The hypothesized treatment mechanism of DBS is through direct or indirect electrical stimulation of targeted neuronal networks that therapeutically modulates their functioning. Therefore, the clinical outcomes of DBS surgery are highly dependent on the precise targeting of the regions of interest where the electrodes will be placed since inaccurate targeting may result in the activation of unintended regions and neurological or psychiatric side-effects. One cause of the inaccuracy in DBS targeting stems from the brain-shift phenomenon which occurs during or after the surgery, usually resolved during the days to weeks following the surgery with the absorption of subdural air. This phenomenon is thought to be due to CSF leakage and intracranial invasion of subdural air during the operation as well as due to the absorption of this subdural air in the post-operative period. Due to brain-shift, despite having advanced techniques in surgical targeting, the post-operative migration of the lead, as well as the hardware deformations related to proximal lead bowing, remains to be a challenge in terms of precise targeting. Considering the impact of brain-shift on target accuracy and hardware-related complications, understanding the mechanism of this phenomenon is significant to develop surgical techniques to counteract it. Despite developing advanced targeting techniques, the determinants of this phenomenon are not yet completely understood. In some studies, it was suggested that brain atrophy could affect the post-operative lead migration, therefore affect the clinical outcomes. In this study, we hypothesized that the extent of brain-shift could be related to biomechanical properties of the brain as a soft tissue, and the degree of the shift of the brain parenchyma in the cranial vault could be affected by the degree of atrophy that the patient already has in the pre-operative stage. Since our aim is not to evaluate disease progression or tissue loss per se, the term “atrophy” refers to the relative size of the brain parenchyma is compared to the intracranial and CSF volumes. Or, in other words, is there a correlation between the amount of atrophy and brain shift that may affect DBS lead location post-surgery.

Gereç ve Yöntem:

In this retrospective study, we evaluated pre-operative 3 Tesla T1 brain MRI of 35 patients, as well as CT scans obtained after 24 hours and 4-6 weeks following the surgery. DBS lead models included Abbott/St. Jude Medical Infinity™, Boston 18 Scientific Vercise™, and Medtronic 3389™. Post-operative CT images are co-registered with 3D slicer software and the degree of proximal lead bowing and the electrode tip displacement were obtained. The degree of the brain atrophy from cross-sectional data (i.e., not longitudinal; one-time obtained brain MRI) was evaluated by comparing 1) total CSF volume / intracranial volume and 2) total ventricle volume/intracranial volume. For GM, WM, CSF, and total intracranial volume segmentation, we used volBrain, which is an automatic and online pipeline for brain segmentation (ref needed). 15 cases were the T1-MRI were obtained with Gd contrast, and the total CSF segmentations were sub-optimal, i.e. the delineation between GM, WM and CSF was interfered with the presence of Gd contrast. Therefore, in those patients, only total ventricle volume/intracranial volume is used as an intra-subject parameter of the brain atrophy. To make the manual corrections on those segmentations, we used ITK-SNAP, which is a software developed explicitly for tissue segmentation. Automatic tissue segmentations and manual corrections were done by one of our researchers who was blinded to the amount of electrode tip displacement and demographic information of each patient.

Bulgular:

We will compare the results for the degree of electrode tip displacement and proximal lead bowing with the extent of the brain atrophy indicated by the total CSF volume and the enlarged ventricles while also considering patient demographics, namely age and sex. It should be noted that there are physiologic volumetric changes in the brain on a daily basis. We will consider this as a limitation factor based on the assumption that the extent of such changes is not prominent enough to interfere with the results significantly. We will also analyze our results for the total volume of subdural air, DBS lead location as well as different DBS lead models.

Sonuç:

Once our analysis is completed, we will announce our results.