Object The authors discuss their method for placement of deep brain stimulation (DBS) electrodes using interventional MR (iMR) imaging and report on the accuracy of the technique, its initial clinical efficacy, and associated complications in a consecutive series of subthalamic nucleus (STN) DBS implants to treat Parkinson disease (PD). Methods A skull-mounted aiming device (Medtronic NexFrame) was used in conjunction with real-time MR imaging (Philips Intera 1.5T). Preoperative imaging, DBS implantation, and postimplantation MR imaging were integrated into a single procedure performed with the patient in a state of general anesthesia. Accuracy of implantation was assessed using 2 types of measurements: the “radial error,” defined as the scalar distance between the location of the intended target and the actual location of the guidance sheath in the axial plane 4 mm inferior to the commissures, and the “tip error,” defined as the vector distance between the expected anterior commissure–posterior commissure (AC-PC) coordinates of the permanent DBS lead tip and the actual AC-PC coordinates of the lead tip. Clinical outcome was assessed using the Unified Parkinson's Disease Rating Scale part III (UPDRS III), in the off-medication state. Results Twenty-nine patients with PD underwent iMR imaging–guided placement of 53 DBS electrodes into the STN. The mean (± SD) radial error was 1.2 ± 0.65 mm, and the mean absolute tip error was 2.2 ± 0.92 mm. The tip error was significantly smaller than for STN DBS electrodes implanted using traditional frame-based stereotaxy (3.1 ± 1.41 mm). Eighty-seven percent of leads were placed with a single brain penetration. No hematomas were visible on MR images. Two device infections occurred early in the series. In bilaterally implanted patients, the mean improvement on the UPDRS III at 9 months postimplantation was 60%. Conclusions The authors' technical approach to placement of DBS electrodes adapts the procedure to a standard configuration 1.5-T diagnostic MR imaging scanner in a radiology suite. This method simplifies DBS implantation by eliminating the use of the traditional stereotactic frame and the subsequent requirement for registration of the brain in stereotactic space and the need for physiological recording and patient cooperation. This method has improved accuracy compared with that of anatomical guidance using standard frame-based stereotaxy in conjunction with preoperative MR imaging.

No abstract

10,11,16 Precise electrode placement within a selected brain region is necessary to achieve efficacy, which is traditionally done with frame-based or "frameless" neuronavigation-guided stereotaxy supported by invasive physiological testing including microelectrode recording. Physiological methods can be used to mitigate the accuracy limitations of stereotactic methods that use a skull-mounted frame or other external markers for spatial registration of brain structures to preoperatively acquired images. 2The iMRI DBS electrode implantation technique utilizes bur hole-mounted trajectory guides oriented toward targets that are defined intraoperatively. The entire procedure is performed within the bore of an MR magnet, with the patient's head positioned at the rear magnet opening for surgical exposure and at the magnet isocenter for target identification, device alignment, and insertion monitoring. The primary benefits of the iMRI technique are high targeting accuracy, reduced operative time, and an ability to directly confirm electrode placement during the procedure. In contrast to conventional stereotactic methods, the iMRI approach is performed with the patient under general anesthesia and does not require intraoperative testing of motor symptoms. obJective The objective of this study was to assess the incidence of postoperative hardware infection following interventional (i)MRI-guided implantation of deep brain stimulation (DBS) electrodes in a diagnostic MRI scanner. methods A diagnostic 1.5-T MRI scanner was used over a 10-year period to implant DBS electrodes for movement disorders. The MRI suite did not meet operating room standards with respect to airflow and air filtration but was prepared and used with conventional sterile procedures by an experienced surgical team. Deep brain stimulation leads were implanted while the patient was in the magnet, and patients returned 1-3 weeks later to undergo placement of the implantable pulse generator (IPG) and extender wire in a conventional operating room. Surgical site infections requiring the removal of part or all of the DBS system within 6 months of implantation were scored as postoperative hardware infections in a prospective database. resUlts During the 10-year study period, the authors performed 164 iMRI-guided surgical procedures in which 272 electrodes were implanted. Patients ranged in age from 7 to 78 years, and an overall infection rate of 3.6% was found. Bacterial cultures indicated Staphylococcus epidermis (3 cases), methicillin-susceptible Staphylococcus aureus (2 cases), or Propionibacterium sp. (1 case). A change in sterile practice occurred after the first 10 patients, leading to a reduction in the infection rate to 2.6% (4 cases in 154 procedures) over the remainder of the procedures. Of the 4 infections in this patient subset, all occurred at the IPG site. conclUsions Interventional MRI-guided DBS implantation can be performed in a diagnostic MRI suite with an infection risk comparable to that reported for traditional surgical placement techniqu...

The presence of high frequency discharge neurons with long periods of silence or "pauses" in the globus pallidus pars externa (GPe) are a unique identifying feature of this nucleus. Prior studies have demonstrated that pause characteristics reflect synaptic inputs into GPe. We hypothesized that GPe pause characteristics should distinguish movement disorders whose basal ganglia network abnormalities are different. We examined pause characteristics in 224 GPe units in patients with primary generalized dystonia, Parkinson's disease (PD), and secondary dystonia, undergoing single unit microelectrode recording for DBS placement in the awake state. Pauses in neuronal discharge were identified using the Poisson surprise method. Mean pause length in primary dystonia (606.8 ±373.3) was higher than in PD (557.4±366.6) (p<0.05). Interpause interval (IPI) was lower in primary dystonia (2331.6±3874.1) than PD (3646.4±5894.5) (p<0.01), and mean pause frequency was higher in primary dystonia (0.14±0.10) than PD (0.07±0.12) (p<0.01). Comparison of pause characteristics in primary versus secondary generalized dystonia revealed a significantly longer mean pause length in primary (606.8±373.3) than in secondary dystonia (495.6±236.5) (p<0.01). IPI was shorter in primary (2331.6±3874.1) than in secondary dystonia (3484.5±3981.6) (p<0.01). The results show that pause characteristics recorded in the awake human GPe distinguish primary dystonia from Parkinson's disease and secondary dystonia. The differences may reflect increased phasic input from striatal D2 receptor positive cells in primary dystonia, and are consistent with a recent model proposing that GPe provides capacity scaling for cortical input.