Simulation to Locate Burr Hole Sites in a Patientfor Deep Brain Stimulation Surgery and Clippingof Intracranial AneurysmKazutaka Kobayashi, MD, PhD*†, Suguru Nakamura, MD†,Mitsuru Watanabe, MD, PhD*†, Kentaro Shimoda, MD, PhD*†,Takashi Morishita, MD, PhD*†, Koichiro Sumi, MD, PhD*†,Toshiharu Otaka, MD, PhD*†, Toshiki Obuchi, MD, PhD*†,Katsunori Shijyo, MD, PhD*†, Toshikazu Kano, MD, PhD*†,Hideki Oshima, MD, PhD*†, Chikashi Fukaya, MD, PhD*†,Takamitsu Yamamoto, MD, PhD*†, Yoichi Katayama, MD, PhD*†

Background and Objective: Deep brain stimulation (DBS) candidates with neurologic diseases such as unruptured aneurysmpresent additional challenges to neurosurgeons when craniotomy must precede DBS surgery. Such craniotomy may potentiallyoverlap with intended burr hole sites for the later insertion of DBS electrodes, and the skin incision for craniotomy may lie veryclose to or intersect with that for the burr holes. We report here a case of forehead craniotomy prior to DBS surgery in which weemployed a neuronavigation system to simulate locations for the craniotomy and burr holes.

Method: A 62-year-old male patient with Parkinson’s disease was a candidate for DBS. He also had an aneurysm and was plannedfirst to undergo frontal craniotomy for clipping before the DBS surgery. The locations of the craniotomy, burr holes, and skinincisions were therefore simulated using a neuronavigation system during craniotomy.

Results: Two weeks after the craniotomy, the patient underwent DBS surgery. Planning software confirmed the absence ofcortical veins beneath the entry points of tentative burr holes and aided trajectory planning. The DBS surgery was performedwithout the interference of the burr holes and head pins and the craniotomy.

Conclusion: Simulation of the locations of craniotomy and burr holes using a neuronavigation system proved valuable in thepresent case of frontal craniotomy before DBS surgery.

Keywords: Deep brain stimulation, frontal craniotomy, neuronavigation, Parkinson’s disease, unruptured aneurysm

Conflict of Interest: The authors reported no conflict of interest.

INTRODUCTION

Deep brain stimulation (DBS) has become widely accepted as aneffective treatment of various involuntary movement disorders suchas Parkinson’s disease (1,2), dystonia (3), and tremors (4).

In DBS candidates with other neurologic diseases such as unrup-tured aneurysm that require craniotomy in the forehead before DBSsurgery, the following issues may arise: 1) the craniotomy mayoverlap with burr hole entry sites for the implantation of DBS elec-trodes and 2) the skin incision for craniotomy may potentially inter-fere with that for burr holes. To address these problems, we reporthere the use of a neuronavigational system for simulating the loca-tions of craniotomy and burr holes in a case of craniotomy in theforehead before DBS surgery.

CASE

The patient was a 62-year-old man with a 17-year history of Parkin-son’s disease. He was followed up by a neurologist and was under

medication. His motor fluctuations and dyskinesia had worsened,and the patient was eventually referred to our hospital for DBSsurgery to improve his motor function. His cognitive status wasassessed by the Mini-Mental State Examination (MMSE), and hisscore was 30/30. Upon referral, computed tomography angiographywas carried out to evaluate intracranial disease, which revealedan aneurysm of the distal anterior cerebral artery. After the

Address correspondence to: Chikashi Fukaya, MD, PhD, Division of AppliedSystem Neuroscience, Department of Advanced Medical Science, Nihon Univer-sity School of Medicine, 30-1 Oyaguchi Kamimachi, Itabashi-ku, Tokyo 173-8610,Japan. Email: fukaya.chikashi@nihon-u.ac.jp

* Division of Applied System Neuroscience, Department of Advanced MedicalScience, Nihon University School of Medicine, Tokyo, Japan; and

† Division of Neurosurgery, Department of Neurological Surgery, Nihon Univer-sity School of Medicine, Tokyo, Japan

For more information on author guidelines, an explanation of our peer reviewprocess, and conflict of interest informed consent policies, please go to http://www.wiley.com/bw/submit.asp?ref=1094-7159&site=1

Neuromodulation: Technology at the Neural Interface

Received: November 14, 2011 Revised: January 16, 2012 Accepted: April 18, 2012

(onlinelibrary.wiley.com) DOI: 10.1111/j.1525-1403.2012.00466.x

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angiography (Fig. 1), we informed the patient concerning the risk ofaneurysm rupture leading to subarachnoid hemorrhage and of therisks associated with surgery for treating an unruptured aneurysm;the patient opted for treatment of his aneurysm. Frontal craniotomyfor the interhemispheric approach for surgical aneurysm clippingwas planned before DBS surgery. It was anticipated that 1) the cran-iotomy might overlap with the burr hole entry sites for DBS elec-trode implantation, 2) the craniotomy might overlap with the headpin of the stereotactic head frame, and 3) the skin incision for cran-iotomy might lie very near or intersect with that for the DBS burrholes. We therefore simulated the locations of the craniotomy, burrholes, and skin incisions using a neuronavigation system.

Gadolinium-enhanced magnetic resonance (MR) imaging of1-mm-thick tissue sections was undertaken preoperatively. Theobtained MR imaging data sets were then transferred into a Stealth-Station® TREON plus navigation system (Medtronic Inc., Minnesota,MN, USA) with installed stereotactic planning software (FrameLink4, Medtronic Inc.) and cranial surgery navigation software (Cranial 5,Medtronic Inc.). The stereotactic planning software was employedfor the bilateral planning of trajectories, including an entry point onthe skin above a space that was shown in the gadolinium-enhancedimages to lack cortical and bridging veins or sulcus (Fig. 2a). Next,images of these planned trajectories were opened in the cranial

Figure 1. Conventional cerebral angiogram through the right internal carotidartery showing an aneurysm of the distal anterior cerebral artery.

Figure 2. Simulation of craniotomy, skin incision for craniotomy, and entry points for bilateral deep brain stimulation (DBS) electrodes using the navigation systemduring clipping surgery. a. FrameLink software-based planning of the trajectory for DBS electrode implantation, including the entry point (arrow) on the skin abovean area free of cortical and bridging veins and sulcus depicted in gadolinium-enhanced magnetic resonance (MR) images. The intersection on each image indicatesthe cortical entry point (upper, left side of trajectory; lower, right side of trajectory). b. Entry points (arrows) on three-dimensional MR images on cranial navigationsoftware. c. Design of craniotomy (white arrowheads), skin incision for craniotomy (black arrowheads), and entry points (arrows) of bilateral DBS electrodes.

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surgery navigation software (Fig. 2b), and the navigation functionwas used to identify tentative locations for the burr hole entrypoints and stereotactic head pins. Optimal locations were devisedso that the bicoronal skin incisions for the clipping surgery wouldcoincide with the DBS burr hole sites and so that the craniotomywould not overlap with the tentative DBS entry points and stereo-tactic frame head pins (Fig. 2c). We measured the distance along theskin incision from the midline to each simulated burr hole location.Clipping surgery was then successfully performed.

After two weeks, the patient underwent surgical implantation ofthe DBS electrode and stimulator. At the time of the surgery, woundwas clear without evidence of infection and his postsurgery coursewas uneventful. His MMSE score was 30/30. Following the adminis-tration of a local anesthetic, a Leksell Frame G (Elekta InstrumentsAB, Stockholm, Sweden) was applied to the patient’s head, andgelatin capsule landmarks were placed along the bicoronal skinincision to delineate the incision on a three-dimensional (3D) MRimage (Fig. 3a). MR images with 1-mm-thick tissue sections wereobtained, and the obtained MR imaging data sets were transferredto the Stealth FrameLink system (FrameLink 4, Medtronic Inc.). First,the simulated burr hole location established at the time of clippingsurgery was identified on the 3D MR image by measuring the dis-tance from the midline along the skin incision for craniotomy(Fig. 3a). Trajectory planning and confirmation of the absence ofcortical veins at the entry point were then accomplished usingStealth FrameLink planning software (FrameLink 4, Medtronic Inc.),

which provided the target coordinates and the angles of the ster-eotactic arc. By setting these coordinates and by the actual insertionof a cannula toward the skin surface on the patient’s head, weidentified the intended burr hole location along the bicoronal skinincision (Fig. 3b). After this process, burr holes were formed imme-diately just below the bicoronal skin incision, avoiding the corticalveins and sulcus according to the predictions made during thesimulation. The burr holes were formed by the “dual-floor” method(5) (Fig. 3c, arrows) to avoid the generation of skin tension, using aburr hole cap and a ring supplied by the electrode manufacturer;such dual-floor burr holes are adjusted to fit the burr hole ring andcap. The electrode and stimulator were implanted permanently(Fig. 3c). After the surgery, the patient showed no cognitive decline(postsurgery MMSE score, 30/30). He did not develop any othersurgical complications such as skin erosion and infection or intrac-ranial bleeding.

DISCUSSION

Unruptured intracranial aneurysms occur with a prevalence of 4.3–6.0% (6,7). Therefore, it is not unusual for a DBS surgery candidate toharbor an unruptured aneurysm.

Neuronavigation is strongly indicated in the targeting of smalland deep intracerebral lesions and in choosing the treatmentoption that will best preserve neurologic function (8). Recently, it

Figure 3. Identification of burr hole sites for deep brain stimulation (DBS) implants. a. Skin incision for craniotomy identified on a three-dimensional magneticresonance (3D MR) image. Upper, bicoronal craniotomy skin incision (arrowheads); middle, gelatin capsules (arrows) placed along the bicoronal skin incision; lower,gelatin capsules (black arrows) identified on the 3D MR image; and simulated locations for burr holes (white arrows). b. Burr hole locations identified on the bicoronalskin incision (arrows). c. 3D computed tomography bone image after DBS surgery. White arrowheads, craniotomy; black arrowheads, DBS electrodes; and arrows, burrholes.

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also has been applied advantageously in other situations such asassisting cranial reconstruction (9).

Intracranial hemorrhage is the most severe complication of DBSsurgery. One cause of such intracranial hemorrhage is the scarifyingof cortical or bridging veins during surgical implantation of the DBSelectrode (10). To avoid this complication, it is essential to identify asufficiently wide cortical field without cortical veins, bridging veins,and sulcus (11). Computer-assisted preoperative trajectory planningwith gadolinium-enhanced stereotactic MR imaging has been rec-ommended in the identification of cortical and bridging veins andthe simulation of burr hole locations (10). Software-based planningprovides the target coordinates and the angles of the stereotacticarc to identify the entry point. With a stereotactic frame affixed tothe patient’s head, one can thus locate the planned burr hole sitesby setting these coordinates without the need for navigation func-tion. However, surgery involving craniotomy without a head framerequires another means of identifying the intended burr hole loca-tion. In such cases, a neuronavigation system is useful at the time ofcraniotomy to simulate the location of burr holes for DBS.

A two-week interval between surgeries may be too short in thelight of the increased risks of bacterial infection and postoperativecognitive dysfunction of the frontal lobe. In our case, the patientshowed no cognitive dysfunction and did not develop any infectionor skin erosion immediately above the burr holes formed by thedual-floor method. However, it is necessary to consider a longerinterval between surgeries and ensure that the wound is notlocated immediately above an area lacks the cranium or an areawith foreign materials to avoid complications.

CONCLUSION

We demonstrated the advantages of using neuronavigational simu-lation for planning the locations of craniotomy and burr holes in apatient requiring craniotomy in the forehead prior to DBS surgery.

Grant Information/Acknowledgements

This work was partly supported by KAKENHI (Nos. 23791616,21591884, and 1591885), Strategic Research Base DevelopmentProgram for Private Universities, and Strategic Research Program forBrain Sciences from the Ministry of Education, Culture, Sports,Science and Technology of Japan.

Authorship Statements

Drs. Kobayashi, Nakamura, Watanabe, Shimoda, Morishita, Sumi,Otaka, Obuchi, Shijyo, Kano, Oshima, and Fukaya designed and con-

ducted the study, including patient recruitment data collection anddata analysis. Dr. Kobayashi prepared the manuscript draft withimportant intellectual input from Drs. Yamamoto and Katayama. Allauthors approved the final manuscript. Drs. Kobayashi and Fukayahad complete access to the study data.

How to Cite this Article:Kobayashi K., Nakamura S., Watanabe M., Shimoda K.,Morishita T., Sumi K., Otaka T., Obuchi T., Shijyo K., KanoT., Oshima H., Fukaya C., Yamamoto T., Katayama Y. 2012.Simulation to Locate Burr Hole Sites in a Patient forDeep Brain Stimulation Surgery and Clipping of Intrac-ranial Aneurysm.Neuromodulation 2012; e-pub ahead of print. DOI:10.1111/j.1525-1403.2012.00466.x

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