Letter to the Editor. ClearPoint versus frame-based MRI-guided and MRI-verified deep brain stimulation

Ludvic Zrinzo MD, FRCS, PhD1, Harith Akram MBChB, FRCS, PhD1, and Marwan Hariz MD, PhD2
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  • 1 UCL Institute of Neurology, Queen Square, London, United Kingdom; and
  • | 2 Umeå University, Umeå, Sweden
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TO THE EDITOR: We read with interest the article by Sharma et al.1 (Sharma VD, Bezchlibnyk YB, Isbaine F, et al. Clinical outcomes of pallidal deep brain stimulation for dystonia implanted using intraoperative MRI [published online October 11, 2019]. J Neurosurg. doi:10.3171/2019.6.JNS19548).

“First do no harm” is a central tenet of medical practice that is especially relevant in functional neurosurgery, where the procedure is supposed to improve quality of life.

The pioneers of stereotactic functional neurosurgery had to rely on ventriculography and stereotactic atlases to guide the initial trajectory, and often performed multiple brain passes while collecting physiological and clinical observations in awake patients under local anesthesia to guide and verify the surgical procedure. The availability of high-quality MRI and commercially available deep brain stimulation (DBS) hardware provides contemporary functional neurosurgeons with an alternative approach. Dedicated stereotactic MRI sequences can be used as follows: 1) to visualize the anatomical target in the specific patient undergoing surgery; 2) to confirm that the DBS lead has reached the intended target; and 3) to refine lead location with one additional brain pass if initial lead placement is suboptimal.

A stereotactic, frame-based approach to MRI-guided and MRI-verified DBS has several benefits. 1) It dispenses with clinical and physiological observations under local anesthesia, reducing patient discomfort as well as the cost involved in terms of equipment and personnel. 2) It allows surgery under general anesthesia, which is especially useful in young children or patients whose symptom severity precludes surgery under local anesthesia. 3) It focuses on lead location within the visible radiological anatomy, which has been increasingly recognized as the best predictor of long-term clinical outcome.2,3 4) It avoids the use of sharp probes within the brain. 5) It minimizes the number of surgical trajectories through the brain. These last 2 factors reduce the risk of damaging vessels, leading to hemorrhage that can result in neurological deficit or death.4 This approach has been shown to deliver clinical results that are equivalent to traditional approaches but with less risk of serious complications.5–8

We are therefore concerned when an MRI-based approach reports high complication rates, especially when 4 of 30 patients suffer an intracerebral hemorrhage, as reported by Sharma et al.1 The discrepancy from other MRI-based approaches might be explained by the surgical technique used in the study.

Instead of using a stereotactic frame to obtain images before and after DBS lead introduction, the ClearPoint system uses “real-time” tracking during introduction of a ceramic stylet and peel-away sheath prior to introduction of the DBS lead. Whereas a frame-based approach requires access to an MRI machine for approximately 20 minutes before and 20 minutes after lead implantation, the ClearPoint system adds considerable cost to an already expensive procedure because it requires high-priced consumables and access to an MRI machine throughout surgery.

The authors argue in favor of a real-time approach by suggesting that “postoperative verification risks delayed recognition of procedural complications.” However, this is a moot point because the options of dealing with a deep-seated hematoma are limited once it has been visualized on MRI. Moreover, it is counterproductive if the new method actually increases the risk of procedural complications. Indeed, bleeds that caused neurological deficit in 2 patients (and ultimately death in 1 patient) “resulted from technical failures related to the introducer peel-away sheath being inserted too deep.”

It is for this reason that we have adopted the modified “KISS” principle in our surgical practice: “Keep It Simple and Safe.” Rather than introducing novel and complex practices to stereotactic functional neurosurgery, we have streamlined the process, removing unnecessary or redundant steps that increase the risk of errors and complications.9 Why fuse a nonstereotactic MR image to a stereotactic CT image to plan the initial trajectory, risking the introduction of co-registration errors, when a stereotactic MR image avoids this? Why use a cannula when the DBS lead will follow the exact path of a rigid probe after it has been removed from the brain? Why perform microelectrode recording when lead location on MRI is a good predictor of long-term outcome? Why perform an MRI study several days after surgery when performing the same investigation while the frame is still on allows the surgeon to relocate a suboptimally placed lead immediately?

The authors are to be congratulated for their in-depth reporting of adverse events and feedback of potential pitfalls to the company when using their equipment. They have emphasized that most of the complications occurred early in their series and are related to adoption of a novel surgical strategy into a busy surgical practice. However, if moving away from frame-based surgery to adopt this more expensive and complex technique was a challenge for such experienced and distinguished functional neurosurgeons, it will certainly test others.

Disclosures

Boston Scientific has provided honoraria and travel expenses to Prof. Hariz for speaking at meetings and to Prof. Zrinzo for attending and presenting at educational activities.

References

  • 1

    Sharma VD, Bezchlibnyk YB, Isbaine F, et al. Clinical outcomes of pallidal deep brain stimulation for dystonia implanted using intraoperative MRI [published online October 11, 2019]. J Neurosurg. doi:10.3171/2019.6.JNS19548

    • Search Google Scholar
    • Export Citation
  • 2

    Avilés-Olmos I, Kefalopoulou Z, Tripoliti E, et al. Long-term outcome of subthalamic nucleus deep brain stimulation for Parkinson’s disease using an MRI-guided and MRI-verified approach. J Neurol Neurosurg Psychiatry. 2014;85:14191425.

    • Search Google Scholar
    • Export Citation
  • 3

    Wodarg F, Herzog J, Reese R, et al. Stimulation site within the MRI-defined STN predicts postoperative motor outcome. Mov Disord. 2012;27(7):874879.

    • Search Google Scholar
    • Export Citation
  • 4

    Zrinzo L, Foltynie T, Limousin P, Hariz MI. Reducing hemorrhagic complications in functional neurosurgery: a large case series and systematic literature review. J Neurosurg. 2012;116(1):8494.

    • Search Google Scholar
    • Export Citation
  • 5

    Burchiel KJ, McCartney S, Lee A, Raslan AM. Accuracy of deep brain stimulation electrode placement using intraoperative computed tomography without microelectrode recording. J Neurosurg. 2013;119(2):301306.

    • Search Google Scholar
    • Export Citation
  • 6

    Chen T, Mirzadeh Z, Chapple K, et al. Complication rates, lengths of stay, and readmission rates in “awake” and “asleep” deep brain simulation. J Neurosurg. 2017;127(2):360369.

    • Search Google Scholar
    • Export Citation
  • 7

    Maldonado IL, Roujeau T, Cif L, et al. Magnetic resonance-based deep brain stimulation technique: a series of 478 consecutive implanted electrodes with no perioperative intracerebral hemorrhage. Neurosurgery. 2009;65(6 Suppl):196202.

    • Search Google Scholar
    • Export Citation
  • 8

    Nakajima T, Zrinzo L, Foltynie T, et al. MRI-guided subthalamic nucleus deep brain stimulation without microelectrode recording: can we dispense with surgery under local anaesthesia? Stereotact Funct Neurosurg. 2011;89(5):318325.

    • Search Google Scholar
    • Export Citation
  • 9

    Zrinzo L. Pitfalls in precision stereotactic surgery. Surg Neurol Int. 2012;3(Suppl 1):S53S61.

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  • 1 Emory University School of Medicine, Atlanta, GA;
  • | 2 University of Kansas Medical Center, Kansas City, KS; and
  • | 3 University of South Florida, Tampa, FL

Response

We appreciate the interest shown by Drs. Zrinzo, Akram, and Hariz in our paper and for taking time to express their concerns. We wholeheartedly agree with the authors that the tenet “first do no harm” is the central principle in medical practice, and an aspiration that guides our surgical practice. Yet, all surgical treatments present risks in the pursuit of benefits; the drive to advance surgical practice, as Zrinzo et al. exemplify, is motivated by the goal to minimize risks in pursuit of greater benefits, and secondarily to decrease resource utilization and expense. Innovation and the use of new technology plays a role in advancing these goals, and indeed that was our impetus to adopt an MRI-guided implantation technique in which a recently developed MRI-based stereotactic platform (which is, in fact, conceptually a stereotactic “frame”) was used.1 Unfortunately, it is all but unavoidable that any new approach or surgical innovation has an associated learning curve to understand and optimize it, by mitigating risks and maximizing efficacy. We reported our efforts in so doing.

Zrinzo et al. do not argue against the acquisition of new technologies; rather, they present an alternative strategy that they have successfully used to improve the effectiveness, safety, and cost of surgical treatment of movement (and other) disorders, for which they are to be congratulated. In contrast to their previously published approach,2 they (personal communication), like us, perform the entire procedure in an intraoperative MRI (iMRI) scanner: the advantage is that the lead can be readily repositioned (if needed) immediately following its insertion—to attain the greatest accuracy without having to return to the operating room (OR) from a nonsterile environment and reopen the incision, etc. Our use of the MRI targeting platform was motivated by the hope that this advantage might decrease if not eliminate the need to reoperate on patients with misplaced leads.

The other motivations for the use of MRI-based procedures are in common between us and Zrinzo et al., as they nicely listed, and they appropriately reference the literature to support both of our approaches. We found similar clinical outcomes in the study group using iMRI and the MRI platform as compared to the conventional stereotactic frame approach (using microelectrode mapping), supporting our view that the pursuit of greater patient comfort does not sacrifice effectiveness. But the authors raised valid concerns about the higher complication rate in the dystonia group who underwent iMRI DBS placement. We acknowledged this concern in our paper and addressed it by several means. First, we assessed all our serious adverse effects to determine how and why they occurred. As mentioned in the Discussion section of our paper, several technical issues became apparent, which were discussed with the manufacturer (ClearPoint System; MRI Interventions, Inc.) and rectified, including the addition of product inserts, revision of protocols, and modifications to physician training. Notably, none of these technical errors and complications occurred in cases treated later in the cohort. Second, because our dystonia group was small, we assessed the incidence of serious adverse events in a larger group by including patients with Parkinson disease (PD) who underwent iMRI-guided globus pallidus internus–DBS placement over the same time interval. In the overall group, the incidence of all serious adverse events (including those due to technical issues as discussed above) was similar to previously reported rates, and none of the patients with PD sustained an intracerebral hemorrhage. This has been discussed briefly in our results and we are in the process of publishing complete data on this cohort of patients with PD. Therefore, based on the present study per se it is too early to say that this method, in its current practice, has a greater complication rate than other techniques.

Zrinzo et al. emphasize that they use a “Keep It Simple and Safe” approach, and suggest avoiding the introduction of “novel and complex practices to stereotactic functional neurosurgery” and “removing unnecessary or redundant steps that increase the risk of errors and complications.”2 We agree with the general premise that reducing unnecessary steps can potentially reduce complications. However, novel technology has been the basis of the advancement of stereotactic and functional neurosurgery practice for more than 75 years. This includes the introduction of the Leksell stereotactic frame and advancing from ventriculography (via CT imaging) to MRI, both of which Zrinzo et al. use and for which they advocate.

Similar to the iMRI platform used in our study, the Leksell frame is a highly specialized piece of equipment that requires specialized training and constant vigilance on the part of the neurosurgeon. However, the ability to reposition a wayward lead at the time of implantation allows neurosurgeons to make sure they get it right prior to the end of the procedure without the need to go back and forth from the MR or CT scanner to the OR (what would be done differently the second time round?), which some surgeons may be more or less inclined to do, given the time, effort, and presumed increased risk of so doing. The other approach that allows this is the use of the intraoperative CT scanner,3,4 which Zrinzo et al. refer to: the negligible registration error between intraoperative CT and preoperative MRI—which is not actually necessary to determine the stereotactic accuracy of the implant—is more than counterbalanced by the ability to reposition the lead if needed without having to break the sterile field, transport the patient to the MRI scanner and then back to the OR for reprepping, etc., to reposition a misplaced or displaced lead. In our workflow, despite the opportunity cost of doing procedures in the diagnostic scanner, the use of MRI time is justified for this reason.

We believe that surgical innovation or inclusion of novel techniques geared toward optimizing patient outcomes is crucial to expand the field of surgery, and to eventually improve patient outcomes. Our objective in this study was to present, in an open and honest way, the sum total of our experience with iMRI-guided DBS placement, and to assess whether the iMRI approach is comparable to other conventional techniques. As with all innovations we did encounter challenges during successfully transitioning to this technique. However, we hope that our experience can guide other centers in adopting this technique. We agree that the long-term cost-effectiveness of this technique has yet to be determined and that future studies comparing different techniques are needed.

References

  • 1

    Larson PS, Starr PA, Bates G, et al. An optimized system for interventional magnetic resonance imaging-guided stereotactic surgery: preliminary evaluation of targeting accuracy. Neurosurgery. 2012;70(1 Suppl Operative):95103.

    • Search Google Scholar
    • Export Citation
  • 2

    Nakajima T, Zrinzo L, Foltynie T, et al. MRI-guided subthalamic nucleus deep brain stimulation without microelectrode recording: can we dispense with surgery under local anaesthesia? Stereotact Funct Neurosurg. 2011;89(5):318325.

    • Search Google Scholar
    • Export Citation
  • 3

    Burchiel KJ, McCartney S, Lee A, Raslan AM. Accuracy of deep brain stimulation electrode placement using intraoperative computed tomography without microelectrode recording. J Neurosurg. 2013;119(2):301306.

    • Search Google Scholar
    • Export Citation
  • 4

    Chen T, Mirzadeh Z, Chapple KM, et al. Clinical outcomes following awake and asleep deep brain stimulation for Parkinson disease. J Neurosurg. 2018;130(1):109120.

    • Search Google Scholar
    • Export Citation

Illustration from Nelson et al. (pp 1516–1526). Artists: Ethan Tyler, Erina He, and Alan Hoofring. Medical Arts, Office of Research Services, National Institutes of Health.

Contributor Notes

Correspondence Ludvic Zrinzo: l.zrinzo@ucl.ac.uk.

INCLUDE WHEN CITING Published online January 17, 2020; DOI: 10.3171/2019.10.JNS192845.

Disclosures Boston Scientific has provided honoraria and travel expenses to Prof. Hariz for speaking at meetings and to Prof. Zrinzo for attending and presenting at educational activities.

  • 1

    Sharma VD, Bezchlibnyk YB, Isbaine F, et al. Clinical outcomes of pallidal deep brain stimulation for dystonia implanted using intraoperative MRI [published online October 11, 2019]. J Neurosurg. doi:10.3171/2019.6.JNS19548

    • Search Google Scholar
    • Export Citation
  • 2

    Avilés-Olmos I, Kefalopoulou Z, Tripoliti E, et al. Long-term outcome of subthalamic nucleus deep brain stimulation for Parkinson’s disease using an MRI-guided and MRI-verified approach. J Neurol Neurosurg Psychiatry. 2014;85:14191425.

    • Search Google Scholar
    • Export Citation
  • 3

    Wodarg F, Herzog J, Reese R, et al. Stimulation site within the MRI-defined STN predicts postoperative motor outcome. Mov Disord. 2012;27(7):874879.

    • Search Google Scholar
    • Export Citation
  • 4

    Zrinzo L, Foltynie T, Limousin P, Hariz MI. Reducing hemorrhagic complications in functional neurosurgery: a large case series and systematic literature review. J Neurosurg. 2012;116(1):8494.

    • Search Google Scholar
    • Export Citation
  • 5

    Burchiel KJ, McCartney S, Lee A, Raslan AM. Accuracy of deep brain stimulation electrode placement using intraoperative computed tomography without microelectrode recording. J Neurosurg. 2013;119(2):301306.

    • Search Google Scholar
    • Export Citation
  • 6

    Chen T, Mirzadeh Z, Chapple K, et al. Complication rates, lengths of stay, and readmission rates in “awake” and “asleep” deep brain simulation. J Neurosurg. 2017;127(2):360369.

    • Search Google Scholar
    • Export Citation
  • 7

    Maldonado IL, Roujeau T, Cif L, et al. Magnetic resonance-based deep brain stimulation technique: a series of 478 consecutive implanted electrodes with no perioperative intracerebral hemorrhage. Neurosurgery. 2009;65(6 Suppl):196202.

    • Search Google Scholar
    • Export Citation
  • 8

    Nakajima T, Zrinzo L, Foltynie T, et al. MRI-guided subthalamic nucleus deep brain stimulation without microelectrode recording: can we dispense with surgery under local anaesthesia? Stereotact Funct Neurosurg. 2011;89(5):318325.

    • Search Google Scholar
    • Export Citation
  • 9

    Zrinzo L. Pitfalls in precision stereotactic surgery. Surg Neurol Int. 2012;3(Suppl 1):S53S61.

  • 1

    Larson PS, Starr PA, Bates G, et al. An optimized system for interventional magnetic resonance imaging-guided stereotactic surgery: preliminary evaluation of targeting accuracy. Neurosurgery. 2012;70(1 Suppl Operative):95103.

    • Search Google Scholar
    • Export Citation
  • 2

    Nakajima T, Zrinzo L, Foltynie T, et al. MRI-guided subthalamic nucleus deep brain stimulation without microelectrode recording: can we dispense with surgery under local anaesthesia? Stereotact Funct Neurosurg. 2011;89(5):318325.

    • Search Google Scholar
    • Export Citation
  • 3

    Burchiel KJ, McCartney S, Lee A, Raslan AM. Accuracy of deep brain stimulation electrode placement using intraoperative computed tomography without microelectrode recording. J Neurosurg. 2013;119(2):301306.

    • Search Google Scholar
    • Export Citation
  • 4

    Chen T, Mirzadeh Z, Chapple KM, et al. Clinical outcomes following awake and asleep deep brain stimulation for Parkinson disease. J Neurosurg. 2018;130(1):109120.

    • Search Google Scholar
    • Export Citation

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