Intraoperative clinical testing overestimates the therapeutic window of the permanent DBS electrode in the subthalamic nucleus

Intraoperative DBS targeting of the globus pallidus internus by using motor evoked potentials

OBJECTIVES

Target localization for deep brain stimulation (DBS) is a crucial step that influences the clinical benefit of the DBS procedure together with the reduction of side effects. In this work, we address the feasibility of DBS target localization in the globus pallidus internus (GPi) aided by intraoperative motor evoked potentials (MEP) with emphasis on the reduction of capsular side effects.

MATERIAL AND METHODS

Micro-macroelectrode recordings were performed intraoperatively on 20 patients that underwent DBS treatment of the GPi (GPi-DBS). MEP were elicited intraoperatively by microelectrode stimulation during stereotactic DBS surgery. We studied the relationship between MEP thresholds and the internal capsule (IC) proximity.

RESULTS

We found a significant correlation between intraoperative MEP thresholds and IC proximity.

CONCLUSIONS

We provide further evidence of the role of MEPs for DBS target localization in the GPi, which extends and confirms the usefulness of MEPs as previously reported by DBS target localization studies dealing with the subthalamic and thalamic nuclei. Our approach is advantageous in that it provides criteria to determine the DBS target without the need to rely on a patient's response while avoiding capsular effects.

Management of essential tremor deep brain stimulation-induced side effects

Deep brain stimulation (DBS) is an effective surgical therapy for carefully selected patients with medication refractory essential tremor (ET). The most popular anatomical targets for ET DBS are the ventral intermedius nucleus (VIM) of the thalamus, the caudal zona incerta (cZI) and the posterior subthalamic area (PSA). Despite extensive knowledge in DBS programming for tremor suppression, it is not uncommon to experience stimulation induced side effects related to DBS therapy. Dysarthria, dysphagia, ataxia, and gait impairment are common stimulation induced side effects from modulation of brain tissue that surround the target of interest. In this review, we explore current evidence about the etiology of stimulation induced side effects in ET DBS and provide several evidence-based strategies to troubleshoot, reprogram and retain tremor suppression.

Intraoperative physiology augments atlas-based data in awake deep brain stimulation

BACKGROUND

Deep brain stimulation (DBS) is commonly performed with patients awake to perform intraoperative microelectrode recordings and/or macrostimulation testing to guide final electrode placement. Supplemental information from atlas-based databases derived from prior patient data and visualised as efficacy heat maps transformed and overlaid onto preoperative MRIs can be used to guide preoperative target planning and intraoperative final positioning. Our quantitative analysis of intraoperative testing and corresponding changes made to final electrode positioning aims to highlight the value of intraoperative neurophysiological testing paired with image-based data to optimise final electrode positioning in a large patient cohort.

METHODS

Data from 451 patients with movement disorders treated with 822 individual DBS leads at a single institution from 2011 to 2021 were included. Atlas-based data was used to guide surgical targeting. Intraoperative testing data and coordinate data were retrospectively obtained from a large patient database. Medical records were reviewed to obtain active contact usage and neurologist-defined outcomes at 1 year.

RESULTS

Microelectrode recording firing profiles differ per track, per target and inform the locations where macrostimulation testing is performed. Macrostimulation performance correlates with the final electrode track chosen. Centroids of atlas-based efficacy heat maps per target were close in proximity to and may predict active contact usage at 1 year. Overall, patient outcomes at 1 year were improved for patients with better macrostimulation response.

CONCLUSIONS

Atlas-based imaging data is beneficial for target planning and intraoperative guidance, and in conjunction with intraoperative neurophysiological testing during awake DBS can be used to individualize and optimise final electrode positioning, resulting in favourable outcomes.

Factors influencing the reliability of intraoperative testing in deep brain stimulation for Parkinson's disease

BACKGROUND

Several meta-analyses comparing the outcome of awake versus asleep deep brain stimulation procedures could not reveal significant differences concerning the postoperative improvement of motor symptoms. Only rarely information on the procedural details is provided for awake operations and how often somnolence and disorientation occurred, which might hamper the reliability of intraoperative clinical testing. The aim of our study was to investigate possible influencing factors on the occurrence of somnolence and disorientation in awake DBS procedures.

METHODS

We retrospectively analyzed 122 patients with Parkinson's disease having received implantation of a DBS system at our centre. Correlation analyses were performed for the duration of disease prior to surgery, number of microelectrode trajectories, AC-PC-coordinates of the planned target, UPDRS-scores, intraoperative application of sedative drugs, duration of the surgical procedure, perioperative application of apomorphine, and the preoperative L-DOPA equivalence dosage with the occurrence of intraoperative somnolence and disorientation.

RESULTS

Patients with intraoperative somnolence were significantly older (p=0.039). Increased duration of the DBS procedure (p=0.020), delayed start of the surgery (p=0.049), higher number of MER trajectories (p=0.041), and the patients' % UPDRS improvement (p=0.046) also correlated with the incidence of intraoperative somnolence. We identified the main contributing factor to intraoperative somnolence as the use of sedative drugs applied during skin incision and burr hole trepanation (p=0.019). Perioperatively applied apomorphine could reduce the occurrence of somnolent phases during the operation (p=0.026).

CONCLUSION

Several influencing factors were found to seemingly increase the risk of intraoperative somnolence and disorientation, while the use of sedative drugs seems to be the main contributing factor. We argue that awake DBS procedures should omit the use of sedatives for best clinical outcome. When reporting on awake DBS surgery these factors should be considered and adjusted for, to permit reliable interpretation and comparison of DBS study results.

The Effects of Different Anesthesia Methods on the Treatment of Parkinson’s Disease by Bilateral Deep Brain Stimulation of the Subthalamic Nucleus

Background

Subthalamic nucleus deep brain stimulation (STN–DBS) surgery for Parkinson’s disease (PD) is routinely performed at medical centers worldwide. However, it is debated whether general anesthesia (GA) or traditional local anesthetic (LA) is superior.

Purpose

This study aims to compare the effects of LA and GA operation methods on clinical improvement in patients with PD, such as motor and non-motor symptoms, after STN–DBS surgery at our center.

Method

A total of 157 patients with PD were retrospectively identified as having undergone surgery under LA (n = 81) or GA (n = 76) states. In this study, the Unified Parkinson’s Disease Rating Scale Motor Score (UPDRS-III) in three states, levodopa-equivalent-daily-dose (LEDD), surgical duration, intraoperative microelectrode recording (iMER) signal length, postoperative intracranial volume, electrode implantation error, neuropsychological function, quality of life scores, and complication rates were collected and compared. All patients with PD were routinely followed up at 6, 12, 18, and 24 months postoperatively.

Result

Overall improvement in UPDRS-III was demonstrated at postoperative follow-up, and there was no significant difference between the two groups in medication-off, stimulation-off state and medication-off, stimulation-on state. However, UPDRS-III scores in medication-on, stimulation-on state under GA was significantly lower than that in the LA group. During postoperative follow-up, LEDD in the LA group (6, 12, 18, and 24 months, postoperatively) was significantly lower than in the GA group. However, there were no significant differences at baseline or 1-month between the two groups. The GA group had a shorter surgical duration, lower intracranial volume, and longer iMER signal length than the LA group. However, there was no significant group difference in electrode implantation accuracy and complication rates. Additionally, the Hamilton Anxiety Scale (HAMA) was significantly lower in the GA group than the LA group at 1-month follow-up, but this difference disappeared at longer follow-up. Besides, there was no significant group difference in the 39-item Parkinson’s Disease Questionnaire (PDQ-39) scale scores.

Conclusion

Although both groups showed overall motor function improvement without a significant postoperative difference, the GA group seemed superior in surgical duration, intracranial volume, and iMER signal length. As the accuracy of electrode implantation can be ensured by iMER monitoring, DBS with GA will become more widely accepted.

Intraoperative vs. Postoperative Side-Effects-Thresholds During Pallidal and Thalamic DBS

Background: It is currently unknown whether results from intraoperative test stimulation of two types of Deep Brain Stimulation (DBS), either during awake pallidal (GPi) or thalamic (Vim), are comparable to the results generated by chronic stimulation through the definitive lead. Objective: To determine whether side-effects-thresholds from intraoperative test stimulation are indicative of postoperative stimulation findings. Methods: Records of consecutive patients who received GPi or Vim were analyzed. Thresholds for the induction of either capsular or non-capsular side-effects were compared at matched depths and at group-level. Results: Records of fifty-two patients were analyzed (20 GPis, 75 Vims). The induction of side-effects was not significantly different between intraoperative and postoperative assessments at matched depths, although a large variability was observed (capsular: GPi DBS: p = 0.79; Vim DBS: p = 0.68); non-capsular: GPi DBS: p = 0.20; and Vim DBS: p = 0.35). Linear mixed-effect models revealed no differences between intraoperative and postoperative assessments, although the Vim had significantly lower thresholds (capsular side-effects p = 0.01, non-capsular side-effects p < 0.01). Unpaired survival analyses demonstrated lower intraoperative than postoperative thresholds for capsular side-effects in patients under GPi DBS (p = 0.01), while higher intraoperative thresholds for non-capsular side-effects in patients under Vim DBS (p = 0.01). Conclusion: There were no significant differences between intraoperative and postoperative assessments of GPi and Vim DBS, although thresholds cannot be directly extrapolated at an individual level due to high variability.

[Deep brain stimulation of the subthalamic nucleus for parkinson's disease: awake vs asleep]

BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is known to be an effective and safe neurosurgical procedure for Parkinson's disease (PD). Traditionally, awake implantation of stimulation system is carried out using microelectrode registration and intraoperative stimulation. Development of neuroimaging technologies enables direct STN imaging. Therefore, asleep surgery without additional intraoperative verification is possible. This approach reduces surgery time and can potentially decrease the incidence of hemorrhagic and infectious complications. The advantages of one method or another are being discussed.

OBJECTIVE

To assess the benefits and limitations of various methods for DBS system implantation for bilateral STN stimulation, to study the issues of stereotaxic accuracy, efficiency and safety of asleep and awake electrode implantation into STN.

MATERIAL AND METHODS

We reviewed the articles published in the PubMed database. Searching algorithm included the following keywords: «asleep DBS», «Parkinson's disease», «subthalamic nucleus», «3T MRI», «SWI», «SWAN».

RESULTS

There were 31 articles devoted to asleep DBS of STN including 4 meta-analyses, 3 prospective controlled studies, 13 retrospective controlled studies and 11 studies without a control group.

CONCLUSION

Asleep implantation of electrodes for DBS of STN can be performed only after a clear imaging of STN boundaries with high-quality MRI.

Adapting the listening time for micro-electrode recordings in deep brain stimulation interventions

PURPOSE

Deep brain stimulation (DBS) is a common treatment for a variety of neurological disorders which involves the precise placement of electrodes at particular subcortical locations such as the subthalamic nucleus. This placement is often guided by auditory analysis of micro-electrode recordings (MERs) which informs the clinical team as to the anatomic region in which the electrode is currently positioned. Recent automation attempts have lacked flexibility in terms of the amount of signal recorded, not allowing them to collect more signal when higher certainty is needed or less when the anatomy is unambiguous.

METHODS

We have addressed this problem by evaluating a simple algorithm that allows for MER signal collection to terminate once the underlying model has sufficient confidence. We have parameterized this approach and explored its performance using three underlying models composed of one neural network and two Bayesian extensions of said network.

RESULTS

We have shown that one particular configuration, a Bayesian model of the underlying network's certainty, outperforms the others and is relatively insensitive to parameterization. Further investigation shows that this model also allows for signals to be classified earlier without increasing the error rate.

CONCLUSION

We have presented a simple algorithm that records the confidence of an underlying neural network, thus allowing for MER data collection to be terminated early when sufficient confidence is reached. This has the potential to improve the efficiency of DBS electrode implantation by reducing the time required to identify anatomical structures using MERs.

Intraoperative Neurophysiologic Assessment in Deep Brain Stimulation Surgery and its Impact on Lead Placement

OBJECTIVES

 While the efficacy of deep brain stimulation (DBS) to treat various neurological disorders is undisputed, the surgical methods differ widely and the importance of intraoperative microelectrode recording (MER) or macrostimulation (MS) remains controversially debated. The objective of this study is to evaluate the impact of MER and MS on intraoperative lead placement.

PATIENTS AND METHODS

 We included 101 patients who underwent awake bilateral implantation of electrodes in the subthalamic nucleus with MER and MS for Parkinson's disease from 2009 to 2017 in a retrospective observational study. We analyzed intraoperative motor outcomes between anatomically planned stimulation point (PSP) and definite stimulation point (DSP), lead adjustments and Unified Parkinson's Disease Rating Scale Item III (UPDRS-III), levodopa equivalent daily dose (LEDD), and adverse events (AE) after 6 months.

RESULTS

 We adjusted 65/202 leads in 47/101 patients. In adjusted leads, MS results improved significantly when comparing PSP and DSP (p < 0.001), resulting in a number needed to treat of 9.6. After DBS, UPDRS-III and LEDD improved significantly after 6 months in adjusted and nonadjusted patients (p < 0.001). In 87% of leads, the active contact at 6 months still covered the optimal stimulation point during surgery. In total, 15 AE occurred.

CONCLUSION

 MER and MS have a relevant impact on the intraoperative decision of final lead placement and prevent from a substantial rate of poor stimulation outcome. The optimal stimulation points during surgery and chronic stimulation strongly overlap. Follow-up UPDRS-III results, LEDD reductions, and DBS-related AE correspond well to previously published data.

Asleep Surgery May Improve the Therapeutic Window for Deep Brain Stimulation of the Subthalamic Nucleus

OBJECTIVE

The effect of anesthesia type in terms of asleep vs. awake deep brain stimulation (DBS) surgery on therapeutic window (TW) has not been investigated so far. The objective of the study was to investigate whether asleep DBS surgery of the subthalamic nucleus (STN) improves TW for both directional (dDBS) and omnidirectional (oDBS) stimulation in a large single-center population.

MATERIALS AND METHODS

A total of 104 consecutive patients with Parkinson's disease (PD) undergoing STN-DBS surgery (80 asleep and 24 awake) were compared regarding TW, therapeutic threshold, side effect threshold, improvement of Unified PD Rating Scale motor score (UPDRS-III) and degree of levodopa equivalent daily dose (LEDD) reduction.

RESULTS

Asleep DBS surgery led to significantly wider TW compared to awake surgery for both dDBS and oDBS. However, dDBS further increased TW compared to oDBS in the asleep group only and not in the awake group. Clinical efficacy in terms of UPDRS-III improvement and LEDD reduction did not differ between groups.

CONCLUSIONS

Our study provides first evidence for improvement of therapeutic window by asleep surgery compared to awake surgery, which can be strengthened further by dDBS. These results support the notion of preferring asleep over awake surgery but needs to be confirmed by prospective trials.

Is awake physiological confirmation necessary for DBS treatment of Parkinson's disease today? A comparison of intraoperative imaging, physiology, and physiology imaging-guided DBS in the past decade

BACKGROUND

Deep brain stimulation (DBS) is a well-established surgical therapy for Parkinson's disease (PD). Intraoperative imaging (IMG), intraoperative physiology (PHY) and their combination (COMB) are the three mainstream DBS guidance methods.

OBJECTIVE

To comprehensively compare the use of IMG-DBS, PHY-DBS and COMB-DBS in treating PD.

METHODS

PubMed, Embase, the Cochrane Library and OpenGrey were searched to identify PD-DBS studies reporting guidance techniques published between January 1, 2010, and May 1, 2018. We quantitatively compared the therapeutic effects, surgical time, target error and complication risk and qualitatively compared the patient experience, cost and technical prospects. A meta-regression analysis was also performed. This study is registered with PROSPERO, number CRD42018105995.

RESULTS

Fifty-nine cohorts were included in the main analysis. The three groups were equivalent in therapeutic effects and infection risks. IMG-DBS (p < 0.001) and COMB-DBS (p < 0.001) had a smaller target error than PHY-DBS. IMG-DBS had a shorter surgical time (p < 0.001 and p = 0.008, respectively) and a lower intracerebral hemorrhage (ICH) risk (p = 0.013 and p = 0.004, respectively) than PHY- and COMB-DBS. The use of intraoperative imaging and microelectrode recording correlated with a higher surgical accuracy (p = 0.018) and a higher risk of ICH (p = 0.049).

CONCLUSIONS

The comparison of COMB-DBS and PHY-DBS showed intraoperative imaging's superiority (higher surgical accuracy), while the comparison of COMB-DBS and IMG-DBS showed physiological confirmation's inferiority (longer surgical time and higher ICH risk). Combined with previous evidence, the use of intraoperative neuroimaging techniques should become a future trend.