Objective: We present a magnetic resonance imaging-directed stereotactic system using implantable guide tubes for targeting deep brain nuclei in functional neurosurgery.
Methods: Our method relies on visualization of the deep brain nuclei on high-resolution magnetic resonance images that delineate the target boundaries and enable direct targeting of specific regions of the nucleus. The delivery system comprises a modified stereoguide capable of delivering an implantable guide tube to the vicinity of the desired target. The guide tube (in-house investigational device) has a hub at its proximal end that is fixed within a burr hole and accommodates a radioopaque stylette that is inserted such that its distal end is at the desired target. After perioperative radiological confirmation of the stylette's relationship to the desired brain target, it is withdrawn from the guide tube, which may then act as a port for the implantation of an electrode for deep brain stimulation (DBS) or radiofrequency lesioning. Alternatively, the guide tube can be used to insert a catheter for drug delivery, cell transplantation, or viral-vector delivery. Implantation and verification are guided by magnetic resonance imaging or computed tomography, which enable the entire procedure to be performed under general anesthesia. The technique of implantation helps ensure optimal accuracy, and we have successfully used this device for implanting electrodes for DBS in the treatment of Parkinson's disease, essential tremor, and dystonia, and for implanting catheters for continuous delivery of glial-derived neurotrophic factor in the treatment of Parkinson's disease. The device also aids in securely fixing the DBS electrode or catheter to the cranium with ease, limiting hardware problems.
Results: A total of 205 guide tubes have been implanted in 101 patients. Major complications in these cases were limited to 4% of patients. At the initial implantations, 96.3% of the guide tubes were within 1.5 mm of the target. Ten guide tubes required reimplantation secondary to target errors. With corrections, the DBS electrode was delivered to within 1.5 mm from the planned target in all cases.
Conclusion: This system provides a safe and accurate magnetic resonance imaging-directed system for targeting deep brain nuclei in functional neurosurgery under general anesthesia and avoids the need for electrophysiological monitoring.