Minimizing Brain Shift during Functional Neurosurgical Procedures - A Simple Burr Hole Technique that can Decrease CSF Loss and Intracranial Air

Background: Exact stereotactic placement of deep brain stimulation electrodes during functional stereotactic neurosurgical procedures can be impeded by intraoperative brain shift. Brain shift has been shown to correlate with the amount of intracranial (subdural) air detected on early postoperative imaging studies. We report a simple burr hole technique that reduces the loss of cerebrospinal fluid (CSF) and has the potential to significantly reduce the amount of postoperative intracranial air. Material and Methods: A total of 16 patients were studied with half (group 2) receiving the burr hole technique designed to seal the CSF space and thereby reducing CSF loss. The other 8 patients (group 1) received the standard burr hole technique. The 2 groups were of similar age, gender, diagnosis (Parkinson's disease, n = 14; cervical dystonia n = 2), and surgical targets. All patients received bilateral electrodes either in the subthalamic nucleus (STN, n = 14) or in the globus pallidum internus (GPi, n = 2) avoiding transventricular trajectories. Early postoperative 3-dimensional computed tomography (3D CT) was used to check for possible bleeding, DBS lead location, and the amount of intracranial air. Intracranial air was assessed manually in a volumetric slice-by-slice approach in the individual postoperative CT and the groups compared by t-test. Results: Group 2 showed significantly lower postoperative intracranial air volumes (4.86 +/- 4.35 cc) as compared to group 1 (27.59 +/- 17.80 cc, p = 0.0083{*}). The duration of surgery, however, was significantly longer for group 1 (435 +/- 56.05 min) as compared to group 2 (316 +/- 34.79 min, p = 0.00015{*}). The time span between the conclusion of the operation and postoperative 3DCT was similar for both groups. Conclusion: This new and simple burr hole technique was associated with a significant reduction in postoperative intracranial air. Reduction of intracranial air will ultimately reduce brain shift. That total operation time does not influence intracranial air is discussed as well as the limitations of this pilot series. In the authors' opinion, this straightforward and cost-effective technique has the potential to reduce brain shift and to increase DBS placement accuracy during functional stereotactic neurosurgical procedures performed in the seated or half-sitting position. A larger more standardized patient series is necessary to substantiate the findings.