Introduction: The success of deep brain stimulation of the internal segment of globus pallidum (GPi DBS) depends on accurately placing the electrode into GPi motor territory. Direct targeting can be difficult as GPi laminar borders are not always clearly identifiable on MRI. Here, we report a method for using the putamen (PUT) as a surrogate anatomical marker to identify GPi, when tissue contrast is inadequate for direct visualization of the GPi DBS target.
Methods: Five patients with Parkinson’s disease were included in this retrospective study. PUT-based GPi targeting was developed using FGATIR MR sequences as follows. The line connecting anterior (AC) and posterior commissure (PC) was drawn, followed by a line (A) through the anterior pole of PUT and parallel to the AC-PC line. The axial length of PUT was then divided into anterior, middle and posterior thirds. A second line (B) was drawn through the border between middle and posterior thirds of PUT. The intersection of A and B corresponded to the optimal location for DBS contact 0 in GPi, based on literature. GPi targeting was compared using PUT-based method vs. consensus coordinate-based indirect targeting. Stereotactic target coordinates were obtained and analyzed.
Results: PUT and GPi in all cases were visualized clearly on FGATIR. GPi borders were not identified on T2, but were localized correctly in all cases using PUT-based method on T2, merged onto FGATIR. Significant differences were noted in Y and Z target coordinates between PUT-based method and indirect targeting (p=0.02 and 0.02), but not X (mean differences for X, Y and Z: 1.5, 3.3 and 6.0 mm).
Conclusions: PUT can be used as a MRI marker for targeting GPi when GPi is not clearly visualized. Further study is planned to correlate PUT-based GPi targeting with microelectrode recording and clinical outcome.
Patient Care: To improve clinical outcomes of patients with dystonia and Parkinson’s disease by targeting GPi more precisely in DBS surgery.
Learning Objectives: To better target GPi in DBS surgery.