Clinical Study

Stereotact Funct Neurosurg Received: June 25, 2019 DOI: 10.1159/000506959 Accepted: February 27, 2020 Published online: June 2, 2020

Deep Brain Stimulation Lead Implantation Using a Customized Rapidly Manufactured Stereotactic Fixture with Submillimetric Euclidean Accuracy

a b b a Tyler J. Ball Kevin D. John Andrew M. Donovan Joseph S. Neimat a b Department of , University of Louisville School of Medicine, Louisville, KY, USA; University of Louisville School of Medicine, Louisville, KY, USA

Keywords no surgical complications. Conclusion: The MicrotableTM Deep brain stimulation · Stereotaxis · Deep brain platform is capable of submillimetric accuracy in patients stimulation accuracy · Frameless stereotaxis · Functional undergoing stereotactic . It has achieved clinical ef- neurosurgery · Movement disorder surgery · Stereotactic ficacy in our patients without surgical complications and has surgery demonstrated the potential for superior accuracy compared to both traditional stereotactic frames and other common frameless systems. © 2020 S. Karger AG, Basel Abstract Background: The microTargetingTM MicrotableTM Platform is a novel stereotactic system that can be more rapidly fabri- cated than currently available 3D-printed alternatives. We Introduction present the first case series of patients who underwent deep brain stimulation (DBS) surgery guided by this platform and Technological advances have enabled significant im- demonstrate its in vivo accuracy. Methods: Ten patients un- provements in the area of stereotactic neurosurgery. New derwent DBS at a single institution by the senior author and technology and refinements of existing technology are 15 leads were placed. The mean age was 69.1 years; four enabling more effective ablation and modulation of dis- were female. The ventralis intermedius nucleus was targeted crete areas of the central nervous system than was possi- for patients with essential tremor and the subthalamic nu- ble in the past. Stereotactic neurosurgery relies on the ac- cleus was targeted for patients with Parkinson’s disease. Re- curacy and precision of targeting systems, whether they sults: Nine DBS leads in 6 patients were appropriately im- are frame-based or frameless. Additionally, given the va- aged to enable measurement of accuracy. The mean Euclid- riety of options now available for stereotaxis and the out- ean electrode placement error (EPE) was 0.97 ± 0.37 mm, and standing accuracy of many systems, the distinction be- the mean radial error was 0.80 ± 0.41 mm (n = 9). In the sub- tween traditional “frame-based and frameless” systems set of CT scans performed greater than 1 month postopera- has been blurred rendering these terms less relevant than tively (n = 3), the mean Euclidean EPE was 0.75 ± 0.17 mm they were in the past. In addition to concerns of accuracy and the mean radial error was 0.69 ± 0.17 mm. There were and precision, clinicians also need to consider patient

© 2020 S. Karger AG, Basel Joseph S. Neimat, MD University of Louisville Department of Neurosurgery, Frazier Rehabilitation Institute [email protected] 220 Abraham Flexner Way, 15th Floor, Louisville, KY 40202 (USA) www.karger.com/sfn joseph.neimat @ ulp.org Downloaded by: East Carolina University - Laupus Library 150.216.132.43 - 6/3/2020 7:30:23 AM comfort, price, and workflow considerations in their hos- pital when choosing a targeting system. The earliest attempt at cranial stereotaxis may have been the encephalometer designed by Dimitrii Zernov in 1889. This rudimentary stereotactic instrument likened

the cranial vault to a globe and referenced cerebral struc- Color version available online tures based off of lines of longitude and latitude, and was modified by Grigorii Rossolimo in 1907 [1]. However, these devices may have been ahead of their time and were not commonly used clinically. The first stereotactic frames to gain widespread clinical acceptance were pio- neered in 1947 by Ernst Spiegel and Henry Wycis, who translated the animal model constructed by Victor Hors- ley and Robert Clarke in the early 20th century. Their frames used as guidance for lo- Fig. 1. The microTargetingTM MicrotableTM Platform, as received calizing the basal ganglia utilizing Cartesian coordinates from the manufacturer. [2]. Then, in 1949, Lars Leksell produced a more refined stereotactic frame known as the Leksell frame, which uti- lized angle, depth, and anterior-posterior coordinates to gineers at Vanderbilt University pioneered a novel device target structures within the brain and allowed greater formally referred to as the microTargetingTM MicrotableTM control of trajectory [3]. Another leap forward came Platform. The device is manufactured by milling a plat- when Brown designed a stereotactic head frame to be form from a planar polycarbonate blank via a computer used in conjunction with a body CT scanner, which in- numerical control (CNC) router. The stereotactic trajec- corporated a localizer we now refer to as the N-bar [4]. tory is achieved by creating precisely recessed holes of Together, these technological advances provided unpar- variable depth and attaching metal legs of appropriate alleled guidance for neurosurgical procedures and helped length based on the stereotactic plan. In the OR, the legs to catalyze the development of and stereo- attach to four bone fiducials that have been previously tactic surgery [5]. placed and used as reference points in the stereotactic Over the past 15 years the increasing availability of vol- plan. The build time for the MicrotableTM Platform is sig- umetric imaging and additive manufacturing (3D print- nificantly reduced compared to the StarFixTM microTar- ing) has enabled the creation of customized stereotactic getingTM Platform such that the bone fiducials can be platforms that can be used for deep brain stimulation placed on the same day as the DBS leads if the mobile (DBS), stereo-EEG, and other stereotactic procedures [6– CNC unit is on-site. The CNC milling requires less than 8]. The application of these technologies has enabled 15 min, and the entire process from receipt of the sur- “frameless” stereotaxis with accuracy comparable to tra- geon’s plan to delivery of the MicrotableTM to sterile pro- ditional rigid frames, increased patient comfort, less “as- cessing requires less than 45 min (including time for mea- sembly” time in the OR and the novel ability to surements to be verified by a third party). The steriliza- simultaneously provide targeting for multiple trajectories tion protocol (for a pre-vacuum wrapped microTableTM) [6–11]. The StarFixTM microTargertingTM Platform is an consists of three preconditioning pulses, an exposure example of a 3D-printed stereotactic system that can pro- time of 4 min at 132 ° C, and, unless immediate use is re- vide these advantages with comparable accuracy to frame- quired, a 25-min drying time. Use of a ONE TRAY® based systems such as the Leksell G frame [12]. A current sealed sterilization container obviates the need for the ad- drawback of additive manufacturing, however, has been ditional drying time. The total sterilization time at our the extended production time required to produce and hospital is around 60 min. prepare the platforms. This has necessitated an addition- As a basis for comparison, construction of the Star- al visit for patients who sometime must travel long dis- FixTM Platform typically requires a 2-day process of man- tances for pre-procedural placement of bone fiducial ufacture, cooling, and preparation and must be done at markers. This has created a desire to explore other manu- remote sites with specialized 3D printers [13]. With the facturing methods to produce a fixture with similar cus- additional shipping time to get the platform to the hospi- tomized stereotactic accuracy. To address this need, en- tal where it will be used, a week between fiducial place-

2 Stereotact Funct Neurosurg Ball/John/Donovan/Neimat DOI: 10.1159/000506959 Downloaded by: East Carolina University - Laupus Library 150.216.132.43 - 6/3/2020 7:30:23 AM Table 1. Patient characteristics

Patient Diagnosis Target Complications

1 ET VIM (bilateral) None 2 PD STN (right) None 3 ET VIM (bilateral) None Color version available online 4 ET VIM (bilateral) None 5 ET VIM (bilateral) None 6 PD STN (right) None 7 ET VIM (left) None 8 ET VIM (left) None 9 ET VIM (bilateral) None 10 PD STN (left) None

ET, essential tremor; PD, Parkinson’s disease; VIM, ventralis intermedius nucleus; STN, subthalamic nucleus.

Fig. 2. The microTargetingTM MicrotableTM Platform, as received from sterile processing. Patients There were 10 patients in this series. The mean age was 69.1 years (range 45–77); 6 were male and 4 were female. Seven were ment and the ultimate is recom- treated for essential tremor (ET) and 3 for Parkinson’s disease mended. (PD). The ventralis intermedius nucleus (VIM) was targeted for ET and the subthalamic nucleus (STN) for PD. Of these patients, Here we present a series of patients for whom we used there were eight VIM leads and one STN lead that had adequate this MicrotableTM Platform (Fig. 1, 2) for stereotaxis in thin-cut postoperative CT scans to enable accuracy calculations. DBS. The MicrotableTM Platform has been rigorously test- See Table 1 for a summary of patient diagnoses and targets. All ed for accuracy and was recently FDA approved. It is a patients also had the StarFixTM microTargetingTM Platform avail- cost-effective and lightweight system that has been shown able for the operation in case of perceived inaccuracy of the Mi- crotableTM system. One additional patient underwent laser inter- to have high accuracy in a series of cochlear implants and stitial thermal therapy (LITT) for mesial temporal lobe ablation comparable accuracy to the StarFixTM Platform in a phan- using the MicrotableTM for stereotaxis. This patient had a good tom model [13–16]. clinical outcome with no complications, but the patient is not in- cluded in this series because there was not a reliable way to deter- mine the accuracy of ablation probe placement with the available Methods imaging.

This retrospective study was reviewed by the University of Lou- Surgical Technique isville Institutional Review Board (IRB) and determined to be ex- DBS took place in three stages (four for bilateral im- empt from full review. All adult patients in the series were evalu- plants), while LITT procedures took place in two stages. Stage 1 ated preoperatively by members of the University of Louisville was identical for both procedures, as was the mounting of the table movement disorders team and presented at the multidisciplinary in stage 2. The workflow for the stages of DBS implantation will be conference. They were approved as appropriate surgical candi- described in the flowing paragraphs. Stage 1 involved fiducial dates and targets were suggested. The MicrotableTM was chosen as placement, stage 2 involved placement of the intracranial elec- the stereotactic device for all patients who would require only uni- trodes, and stage 3 involved placement of the implantable pulse lateral procedures or for whom the left and right sides would be generator (IPG). For 2 patients, the MicrotableTM Platform was cut staged in separate procedures (typically patients over the age of 70 and assembled on site, enabling stages 1 and 2 to be completed on or patients expected to fatigue with a longer surgery). The Star- the same day. In other cases, stage 1 generally took place as an out- FixTM Platform was used for patients undergoing simultaneous bi- patient approximately 1 week prior to lead placement. Four small lateral procedures as it allows multiple trajectories using the same scalp incisions were made and bone fiducials (WayPoint Fiducial platform. All procedures took place at a single institution and were Anchors; FHC, Inc.) were placed in the operating room. A thin-cut performed by the senior author (J.S.N.) from January 2018 to Jan- (0.6 mm) head CT was obtained the same day. The stereotactic CT uary 2019. All patients received a postoperative CT scan of the scan was then co-registered with the stereotactic MRI in the Way- head to rule out surgical hemorrhages. An additional high-resolu- PointTM Navigator software. The appropriate trajectory was then tion CT scan was obtained 1 month or greater after surgery to cal- planned, and the plan was uploaded to a secure FHC online data- culate accuracy without the confounding factor of pneumocepha- base. The measurements were then transferred to the facility that lus. fabricates the MicrotableTM. After assembly of the MicrotableTM

DBS Lead Implantation Using Stereotact Funct Neurosurg 3 MicrotableTM DOI: 10.1159/000506959 Downloaded by: East Carolina University - Laupus Library 150.216.132.43 - 6/3/2020 7:30:23 AM Color version available online

a b c

Fig. 3. a Standoffs shown screwed into preexisting fiducial anchors (not visible). b Microtable platform attached to standoffs. c Final setup.

Platform, confirmatory measurements were taken manually and Euclidean distance between the planned target and the bottom of sent to a third party to verify the accuracy of the table. The Mi- the deepest lead. Of note, some authors have used the centroid of crotableTM Platform was then sent to the hospital where sterile pro- the lead between the second and third contacts as the “target,” cessing was performed, and it was made ready for use. On the day which differs from our methodology. Given the differences in of electrode implantation (stage 2), the skin was re-opened over spacing between leads, it has been the practice of the senior author the fiducial anchors and standoffs were placed (Fig. 3a). The Mi- to place the bottom of the deepest lead at the “target.” We also crotableTM was then mounted to the standoffs (Fig. 3b), and a computed the error perpendicular to the axis of the lead, the “ra- straight trocar passed through a guide that sits in the opening of dial error.” The Euclidean distance between two points is defined the MicrotableTM to approximate the location of the intended burr as the square root of the sum of the squares of the differences be- hole. Next, the skin incision was made, and the trocar was used to tween the corresponding coordinates of the points on the x, y, and mark the exact center of the burr hole. After making the burr hole z axes [12]. and opening the dura and pia, the microTargetingTM STarTM Drive was attached to the MicrotableTM (Fig. 3c). The surgery then pro- ceeded as usual. Multi-electrode microelectrode recording and macrostimulation (“Ben-gun” technique) was used for all DBS cas- Results es. We typically recorded with arrays of 3–4 microTargetingTM electrodes and performed stimulation using the macroelectrode tip [17]. Once the optimal track and position were chosen, we Nine DBS leads in 6 patients were appropriately im- inserted the final DBS electrode and secured it using a titanium aged to enable measurement of accuracy. Eight were tar- hemoclip and bone cement as described by White-Dzuro et al. geted at the VIM and 1 was targeted at the STN. Three of [18]. these leads were imaged over 1 month from surgery, at a Stage 3, IPG placement, also took place as an outpatient, except time when pneumocephalus had resolved. In 4 patients, in cases where a contralateral implant was already in place. In those cases, the new lead was connected to the existing IPG during stage the postoperative imaging was obtained using 5-mm- 2. In the case of new bilateral leads, the leads were placed on sepa- thick CT slices that were insufficient to determine place- rate days, usually at least a week apart. ment accuracy. No patient was noted to have hemorrhage in either the high- or low-resolution group. There were Accuracy Calculations no surgical complications as of the last clinical follow-up For calculation of the electrode placement error (EPE), patients needed a postoperative thin-cut CT scan. These were available for for all patients. 8 VIM leads and 1 STN lead (2 of the patients with PD did not get The overall mean Euclidean EPE was 0.97 ± 0.37 mm, a thin-cut postoperative CT scan). The EPE was calculated as the and the mean radial error was 0.80 ± 0.41 mm (n = 9)

4 Stereotact Funct Neurosurg Ball/John/Donovan/Neimat DOI: 10.1159/000506959 Downloaded by: East Carolina University - Laupus Library 150.216.132.43 - 6/3/2020 7:30:23 AM Table 2. Electrode placement error (EPE) for cases with high-resolution follow-up imaging

Target Euclidean EPE, mm Radial EPE, mm within 24 h post-op delayed scan within 24 h post-op delayed scan

L VIM 1.68 (2 wk) 1.66 (2 wk) R VIM 0.78 0.65 L VIM 1.39 1.20 L VIM 0.58 0.51 R VIM 0.99 0.31 L VIM 0.64 (1 mo) 0.54 (1 mo) L VIM 0.67 (2 mo) 0.65 (2 mo) R VIM 0.94 (2 mo) 0.88 (2 mo) L STN 1.02 0.82 Overall mean (n = 9) 0.97±0.37 0.80±0.41 Mean for measurements taken ≥1 month post-op (n = 3) 0.75±0.17 0.69±0.17

L, left; R, right; VIM, ventralis intermedius nucleus; STN, subthalamic nucleus; wk, weeks; mo, month(s).

(Table 2). More specifically, the mean deviations for the formed a meta-analysis of frame-based and frameless sys- leads were 0.45 ± 0.57 mm in the lateral direction, 0.09 ± tems and found a statistically significant loss of accuracy 0.54 mm in the anterior direction, and 0.22 ± 0.48 mm in with frameless methods, albeit of questionable clinical the superior direction (Table 3). When measured on CT significance. Notably, when including asleep DBS with scans taken greater than 1 month postoperatively (n = 3), intraoperative image guidance, Ostrem and colleagues the mean Euclidean EPE was 0.75 ± 0.17 mm and the [22] demonstrated a mean radial error of 0.6 mm ± 0.3 mean radial error was 0.69 ± 0.17 mm. mm with the ClearPoint system. This is the highest accu- racy we have seen reported for DBS, with which our re- sults compare favorably. It is notable that the MRI-guided Discussion technique allows intraoperative imaging and adjustment of trajectory, unlike other frame-based and frameless ste- The MicrotableTM Platform has been successfully im- reotactic systems discussed here. However, the MRI- plemented in studies for percutaneous cochlear implants guided technique requires either intraoperative MRI or and virtual DBS targets, but this is the first study to test the ability to set up a temporary operating theatre in an the accuracy of the system in DBS clinically [13–16]. MRI suite, which may not be available in all hospitals. The EPE of 0.97 ± 0.37 mm for this series of patients is Furthermore, other techniques report error of lead place- smaller than any frame-based study to our knowledge, ment with respect to preoperative imaging, which does which has traditionally been the “gold standard” for ste- not have the confounding effect of pneumocephalus. The reotaxis. The lowest recorded target accuracy published error reported by Ostrem and colleagues [22] is based off for a frame-based system is 1.2 mm for the Leksell G the “2D vector difference between the intended and ac- frame, reported by Bjartmarz and Rehncrona [19]. The tual lead placement measured in the axial plane used for other platform that we use heavily at our institution, the anatomical targeting.” This is significant because mea- StarFixTM Platform, has a reported EPE of 1.99 ± 0.92 mm surements from the lead to the intended target taken on when brain shift from pneumocephalus is not accounted the intraoperative MRI would not have the confounding for, and 1.24 mm ± 0.37 mm when brain shift is account- effect of pneumocephalus. Even though pneumocephalus ed for (n = 75 patients) [8, 12]. In a study comparing 119 is present, direct measurements are taken between a lead Leksell frame-based DBS and 78 Nexframe DBS electrode and target rather than comparing the Euclidean coordi- implantations, a mean error of 2.5 ± 1.2 mm was found nates of the intended target on the preoperative scan for the Leksell frame and 2.8 ± 1.3 mm for the Nexframe (without pneumocephalus) with the Euclidean coordi- [20]. As recently as 2018, Roth and colleagues [21] per- nates of the lead on the postoperative scan, which did

DBS Lead Implantation Using Stereotact Funct Neurosurg 5 MicrotableTM DOI: 10.1159/000506959 Downloaded by: East Carolina University - Laupus Library 150.216.132.43 - 6/3/2020 7:30:23 AM Table 3. Directionality of lead deviation

Target Intended target coordinates Actual target coordinates Direction of deviation, mm** with respect to the MCP, mm* with respect to the MCP, mm

L VIM x: 11.79 x: 13.30 x: 1.47 y: 7.31 y: 6.98 y: –0.33 z: 0.17 z: 0.91 z: 0.745 R VIM x: 12.48 x: 13.23 x: 0.75 y: 5.70 y: 5.62 y: –0.08 z: 0.01 z: 0.17 z: 0.16 L VIM x: 16 x: 15.35 x: –0.65 y: 8 y: 9.22 y: 1.22 z: 0 z: 0.12 z: 0.12 L VIM x: 13.13 x: 13.53 x: 0.40 y: 8 y: 8.16 y: 0.16 z: 0.71 z: 1.10 z: 0.39 R VIM x: 15.22 x: 15.38 x: 0.16 y: 8 y: 7.52 y: –0.48 z: 0 z: 0.85 z: 0.85 L VIM x: 13.85 x: 14.06 x: 0.21 y: 6.81 y: 6.21 y: –0.60 z: 0.27 z: 0.34 z: 0.07 L VIM x: 11.39 x: 12.06 x: 0.67 y: 6.86 y: 6.86 y: 0.00 z: 0.84 z: 0.83 z: –0.02 R VIM x: 12.07 x: 12.99 x: 0.92 y: 5.91 y: 6.06 y: 0.15 z: 0.78 z: 0.92 z: 0.14 L STN x: 11.12 x: 11.22 x: 0.10 y: 4.01 y: 4.59 y: 0.58 z: 5.68 z: 4.85 z: –0.83 Mean x: 0.45±0.57 y: 0.09±0.54 z: 0.22±0.48

* x coordinate denotes medial/lateral, y coordinate denotes anterior/posterior, z coordinate denotes inferior/superior. ** x: positive numbers denote lateral deviation, y: positive numbers denote posterior deviation from the intended target with respect to the MCP, z: positive numbers denote superior deviation. MCP, midcommissural point; L, left; R, right; VIM, ventralis intermedius nucleus; STN, subthalamic nucleus. have pneumocephalus. Notably, when looking only at the 0.22 ± 0.48 mm in the z plane all had a high standard de- subset of patients who had delayed scans (> 1 month post- viation with respect to the absolute values of the in-plane operatively) without pneumocephalus, the mean radial deviations. error was only 0.69 ± 0.17 mm. Furthermore, the root- While the number of patients in this series is small, the mean square for the ClearPoint system is the same as that results are encouraging and suggest that the MicrotableTM of the Microtable system when looking at leads imaged Platform may have a place in stereotactic neurosurgery. without pneumocephalus (0.7 mm for both). Regarding It also challenges the long-standing notion that frame- the direction of deviation using the current frame, no based systems are the “gold standard” for stereotaxis, strong tendency was observed. The deviations of 0.45 ± which is particularly important given the changing scope 0.57 mm in the x plane, 0.09 ± 0.54 mm in the y plane, and of stereotaxis in neurosurgery and the number of engi-

6 Stereotact Funct Neurosurg Ball/John/Donovan/Neimat DOI: 10.1159/000506959 Downloaded by: East Carolina University - Laupus Library 150.216.132.43 - 6/3/2020 7:30:23 AM neering technologies that are being brought to bear on 2 of the patients had only 5 mm slice thickness CT scans, stereotactic surgery. which were inadequate to determine stereotactic accura- As an increasing number of therapies (LITT, convec- cy. This biased the cohort such that nearly all of the DBS tion enhanced delivery, etc.) require precise stereotactic leads used to calculate accuracy were for ET patients. Fur- access, there may be significant value in a rapidly custom- thermore, the fact that all procedures were carried out at izable platform like the MicrotableTM if it provides excep- a single institution by one who has been using a tional accuracy. While there are other easy-to-use sys- similar system for over 10 years may limit the generaliz- tems available to neurosurgeons, such as the VarioGuide, ability of the results. Larger studies directly comparing their accuracy for deep-seated lesions is debatable. Bra- stereotactic platforms (e.g., StarFixTM vs. MicrotableTM) in dac and colleagues [23] compared the VarioGuide system similar cohorts of patients done by centers with experi- to a CRW frame and found a mean target error of 2.65 ± ence with similar platforms may further elucidate the 1.12 mm in the frame-based group and 2.90 ± 1.26 mm benefits and limitations of each platform. Additionally, a in the VarioGuide group, a difference which was not more detailed cost analysis would be helpful to determine found to be statistically significant (p = 0.456). However, the more cost-effective system, especially considering the the difference in angular deviation between the groups more common case of institutions with a lower volume of approached statistical significance (p = 0.074) and was DBS. slightly lower in the frame-based group (2.62 ± 1.31 de- grees vs. 3.49 ± 2.05 degrees in the VarioGuide group). This difference is important because the error will be am- Conclusion plified for longer trajectories, and the lengths of planned trajectories in that study were relatively short compared In this study, we have validated that the MicrotableTM to the trajectories that would be used for DBS or for bi- Platform is capable of submillimetric accuracy in a small opsy of deep-seated lesions (the mean trajectory length cohort of patients. It has achieved clinical efficacy in our was 44.20 ± 13.93 mm in the frame-based group and patients without surgical complications and has demon- 39.83 ± 11.20 mm in the VarioGuide group). Addition- strated the potential for superior accuracy compared to ally, patient comfort should factor into the decision-mak- both traditional stereotactic frames and other frameless ing algorithm when choosing a stereotactic frame. Bradac systems. and colleagues [23] found a significant difference in the discomfort experienced by patients undergoing frame- Statement of Ethics based stereotactic as opposed to frameless stereo- tactic biopsy (visual analog score of 2.5 ± 2.1 in frame- The authors have no ethical conflicts to disclose. based cases vs. 1.2 ± 0.6 in VarioGuide cases [p = 0.004]) [23]. Finally, cost should factor into the decision of which system to use. A 2002 study found the capital costs for a Disclosure Statement CRW frame of GBP 86,698 with an annual service con- tract GBP 2,500 [9]. Accounting for inflation and ex- Tyler J. Ball, Kevin D. John, and Andrew M. Donovan have no disclosures relevant to this study. Dr. Neimat: limited consulting change rate, this is around USD 165,000–180,000 with an for Abbott and Medtronic. annual maintenance cost of around USD 5,000. By com- parison, the MicrotableTM system is in the range of USD 3,000 for a unilateral DBS platform (professional com- Funding Sources munication with FHC representative). For high-volume centers, the frame may prove cost-effective when looking None. at material costs alone. However, one must also consider the added procedural time of placing the frame, especial- ly if the frame is placed in the operating room and billed Author Contributions as anesthesia time. Limitations of this study include the lack of complete Tyler J. Ball and Joseph S. Neimat performed accuracy calcula- tions. Tyler J. Ball, Kevin D. John, Andrew M. Donovan, and Jo- postoperative imaging for all patients at 1 month and the seph S. Neimat prepared the manuscript. Joseph S. Neimat was the small sample size. Additionally, of the 3 patients with PD senior neurosurgeon responsible for the care of the patients in this in this sample who underwent DBS with the MicrotableTM, case series.

DBS Lead Implantation Using Stereotact Funct Neurosurg 7 MicrotableTM DOI: 10.1159/000506959 Downloaded by: East Carolina University - Laupus Library 150.216.132.43 - 6/3/2020 7:30:23 AM References

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8 Stereotact Funct Neurosurg Ball/John/Donovan/Neimat DOI: 10.1159/000506959 Downloaded by: East Carolina University - Laupus Library 150.216.132.43 - 6/3/2020 7:30:23 AM