Electrophysiologic Validation of Diffusion Tensor Imaging Tractography during Deep Brain Stimulation Surgery

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Eleven patients underwent subthalamic nucleus deep brain stimulation. DTI and high-resolution T1- and T2-weighted MRI were performed at 3T. The electrode positions and current amplitudes that elicited corticospinal tract effects during the operation were studied to determine relative corticospinal tract distance. The mean intraoperative electrophysiologic corticospinal tract distance was 3.0 mm +/- 0.6 mm; the mean image-derived corticospinal tract distance (DTI fiber tractography) was 3.0 mm +/- 1.3 mm. DTI fiber tractography depicted the medial corticospinal border in concordance with electrophysiology under 2 different conditions and modeling approaches. Under both conditions, the electrophysiologic measurements were clearly related to the DTI fiber tractography.

Abstract

Figure 2 from paper
3D renditions of the corticospinal tract. A, Depiction of a left CST (red) in the fiber-tracking software (StealthViz DTI; Medtronic) but already depicted as a DICOM hull structure. B, Bilateral visualization of the transferred DICOM structure in the planning software (FrameLink 5.0; Medtronic Surgical Navigation). Blue probe simulations indicate intraoperatively tested electrode positions (test el.). PG indicates precentral gyrus; test el. (sim.), simulated test electrode position.

BACKGROUND AND PURPOSE

Diffusion tensor imaging fiber tractography–assisted planning of deep brain stimulation is an emerging technology. We investigated its accuracy by using electrophysiology under clinical conditions. We hypothesized that a level of concordance between electrophysiology and DTI fiber tractography can be reached, comparable with published modeling approaches for deep brain stimulation surgery.

MATERIALS AND METHODS

Eleven patients underwent subthalamic nucleus deep brain stimulation. DTI scans and high-resolution T1- and T2-weighted MR imaging was performed at 3T. Corticospinal tracts were traced. We studied electrode positions and current amplitudes that elicited corticospinal tract effects during the operation to determine relative corticospinal tract distance. Postoperatively, 3D deep brain stimulation electrode contact locations and stimulation patterns were applied for the same corticospinal tract distance estimation.

RESULTS

Intraoperative electrophysiologic (n = 40) clinical effects in 11 patients were detected. The mean intraoperative electrophysiologic corticospinal tract distance was 3.0 ± 0.6 mm; the mean image-derived corticospinal tract distance (DTI fiber tractography) was 3.0 ± 1.3 mm. The 95% limits of agreement were ±2.4 mm. Postoperative electrophysiology (n = 44) corticospinal tract activation effects were encountered in 9 patients; 39 were further evaluated. Mean electrophysiologic corticospinal tract distance was 3.7 ± 0.7 mm; for DTI fiber tractography, it was 3.2 ± 1.9 mm. The 95% limits of agreement were ±2.5 mm.

CONCLUSIONS

DTI fiber tractography depicted the medial corticospinal tract border with proved concordance. Although the overall range of measurements was relatively small and variance was high, we believe that further use of DTI fiber tractography to assist deep brain stimulation procedures is advisable if inherent limitations are respected. These results confirm our previously published electric field simulation studies.

 

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Electrophysiologic Validation of Diffusion Tensor Imaging Tractography during Deep Brain Stimulation Surgery
jross
Jeffrey Ross • Mayo Clinic, Phoenix

Dr. Jeffrey S. Ross is a Professor of Radiology at the Mayo Clinic College of Medicine, and practices neuroradiology at the Mayo Clinic in Phoenix, Arizona. His publications include over 100 peer-reviewed articles, nearly 60 non-refereed articles, 33 book chapters, and 10 books. He was an AJNR Senior Editor from 2006-2015, is a member of the editorial board for 3 other journals, and a manuscript reviewer for 10 journals. He became Editor-in-Chief of the AJNR in July 2015. He received the Gold Medal Award from the ASSR in 2013.