Validation of the hotspot for dorsolateral subthalamic nucleus targeting in deep brain stimulation surgery for Parkinson's disease: a post hoc analysis of a randomised controlled trial.

BACKGROUND: Visualisation of the dorsolateral subthalamic nucleus (STN) remains challenging on 1.5 and 3Tesla T2-weighted MRI. Our previously defined hotspot, relative to the well-visualised medial STN border, serves as an MRI landmark for dorsolateral STN identification in deep brain stimulation (DBS). We aimed to validate this hotspot in a separate trial cohort of Parkinson's disease (PD) patients and refine its location. METHODS: In this post hoc analysis of a randomised controlled trial, in which the hotspot was taken into account during target planning, responses to DBS were evaluated using hemibody improvement on the Movement Disorder Society-Unified Parkinson's Disease Rating Scale motor examination and compared with our historical cohort, as well as dopaminergic medication reduction. Then, a refined hotspot was calculated and the Euclidean distance from individual active contacts to the refined hotspot was correlated with motor improvement. RESULTS: The first quartile of the hemibodies (poor responders) showed an average improvement of 13%, which was higher than the -8% in the historical control group (p=0.044). Dopaminergic medication reduction was greater in the current cohort compared with the historical cohort (p=0.020). Overall variability of hemibody motor improvement was reduced in the current cohort compared with the historical control group (p=0.003). Motor improvement correlated to the Euclidean distance from active contact to the refined hotspot (2.8 mm lateral, 1.1 mm anterior and 2.2 mm superior to the medial STN border) (p=0.001). CONCLUSION: We validated the hotspot for dorsolateral STN targeting in DBS for patients with PD and showed an improved motor response in poor responders, a reduced variability in motor improvement and a greater dopaminergic medication reduction. We then refined the hotspot at 2.8 mm lateral, 1.1 mm anterior and 2.2 mm superior relative to the medial STN border, which visualises a readily implementable target within the dorsolateral STN on lower field strength MRI.

Cognitive and psychiatric outcomes in the GALAXY trial: effect of anaesthesia in deep brain stimulation.

BACKGROUND: This study aims: (1) To compare cognitive and psychiatric outcomes after bilateral awake versus asleep subthalamic nucleus (STN) deep brain stimulation (DBS) surgery for Parkinson's disease (PD). (2) To explore the occurrence of psychiatric diagnoses, cognitive impairment and quality of life after surgery in our whole sample. (3) To validate whether we can predict postoperative cognitive decline. METHODS: 110 patients with PD were randomised to receive awake (n=56) or asleep (n=54) STN DBS surgery. At baseline and 6-month follow-up, all patients underwent standardised assessments testing several cognitive domains, psychiatric symptoms and quality of life. RESULTS: There were no differences on neuropsychological composite scores and psychiatric symptoms between the groups, but we found small differences on individual tests and cognitive domains. The asleep group performed better on the Rey Auditory Verbal Learning Test delayed memory test (f=4.2, p=0.04), while the awake group improved on the Rivermead Behavioural Memory Test delayed memory test. (f=4.4, p=0.04). The Stroop III score was worse for the awake group (f=5.5, p=0.02). Worse scores were present for Stroop I (Stroop word card) (f=6.3, p=0.01), Stroop II (Stroop color card) (f=46.4, p<0.001), Stroop III (Stroop color-word card) (f=10.8, p=0.001) and Trailmaking B/A (f=4.5, p=0.04). Improvements were seen on quality of life: Parkinson's Disease Questionnaire-39 (f=24.8, p<0.001), and psychiatric scales: Hamilton Depression Rating Scale (f=6.2, p=0.01), and Hamilton Anxiety Rating Scale (f=5.5, p=0.02). CONCLUSIONS: This study suggests that the choice between awake and asleep STN DBS does not affect cognitive, mood and behavioural adverse effects, despite a minor difference in memory. STN DBS has a beneficial effect on quality of life, mood and anxiety symptoms. TRIAL REGISTRATION NUMBER: NTR5809.

Surgical Complications in Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease: Experience in 800 Patients.

INTRODUCTION: We present our surgical complications resulting in neurological deficit or additional surgery during 25 years of DBS of the subthalamic nucleus (STN) for Parkinson's disease (PD). METHODS: We conducted a retrospective chart review of all PD patients that received STN DBS in our DBS center between 1998 and 2023. Outcomes were complications resulting in neurological deficit or additional surgery. Potential risk factors (number of microelectrode recording tracks, age, anesthesia method, hypertension, and sex) for symptomatic intracerebral hemorrhage (ICH) were analyzed. Furthermore, lead fixation techniques were compared. RESULTS: Eight hundred PD patients (507 men, 293 women) received unilateral (n = 11) or bilateral (n = 789) implantation of STN electrodes. Neurological deficit due to ICH, edema, delirium, or infarction was seen in 8.4% of the patients (7.4% transient, 1.0% permanent). Twenty-two patients (2.8%) had a symptomatic ICH following STN DBS, for which we did not find any risk factors, and five had permanent sequelae due to ICH (0.6%). Of all patients, 18.4% required additional surgery; the proportion was reduced from 27% in the first 300 cases to 13% in the last 500 cases (p < 0.001). The infection rate was 3.5%, which decreased from 5.3% in the first 300 cases to 2.2% in the last 500 cases. The use of a lead anchoring device led to significantly less lead migrations than miniplate fixation. CONCLUSION: STN DBS leads to permanent neurological deficit in a small number of patients (1.0%), but a substantial proportion needs some additional surgical procedure after the first DBS system implantation. The risk of revision surgery was reduced over time but remained significant. These findings need to be discussed with the patient in the preoperative informed consent process in addition to the expected health benefit.

Programming Algorithm for the Management of Speech Impairment in Subthalamic Nucleus Deep Brain Stimulation for Parkinson's Disease.

OBJECTIVES: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson's disease (PD) has an ambiguous relation to speech. Speech impairment can be a stimulation-induced side effect, and parkinsonian dysarthria can improve with STN-DBS. Owing to the lack of an up-to-date and evidence-based approach, DBS reprogramming for speech impairment is largely blind and greatly relies on the physician's experience. In this study, we aimed to establish an evidence- and experience-based algorithm for managing speech impairment in patients with PD treated with STN-DBS. MATERIALS AND METHODS: We performed a single-center retrospective study to identify patients with STN-DBS and speech impairment. Onset of speech impairment, lead localization, and assessment of DBS-induced nature of speech impairment were collected. When DBS settings were adjusted for improving speech, the magnitude and duration of effect were collected. We also performed a systematic literature review to identify studies describing the effects of parameter adjustments aimed at improving speech impairment in patients with PD receiving STN-DBS. RESULTS: In the retrospective study, 245 of 631 patients (38.8%) with STN-DBS had significant speech impairment. The probability of sustained marked improvement upon reprogramming was generally low (27.9%). In the systematic review, 23 of 662 identified studies were included. Only two randomized controlled trials have been performed, providing evidence for interleaving-interlink stimulation only. Considerable methodologic heterogeneity precluded the conduction of a meta-analysis. CONCLUSIONS: Speech impairment in STN-DBS for PD is frequent, but high-quality evidence regarding DBS parameter adjustments is scarce, and the probability of sustained improvement is low. To improve this outcome, we propose an evidence- and experience-based approach to address speech impairment in STN-DBS that can be used in clinical practice.

Probabilistic Mapping Reveals Optimal Stimulation Site in Essential Tremor.

OBJECTIVE: The objective of this study was to obtain individual clinical and neuroimaging data of patients undergoing deep brain stimulation (DBS) for essential tremor (ET) from 5 different European centers to identify predictors of outcome and to identify an optimal stimulation site. METHODS: We analyzed retrospectively baseline covariates, pre- and postoperative clinical tremor scores (for 12 months) as well as individual imaging data from 119 patients to obtain individual electrode positions and stimulation volumes. Individual imaging and clinical data were used to calculate a probabilistic stimulation map in normalized space using voxel-wise statistical analysis. Finally, we used this map to train a classifier to predict tremor improvement. RESULTS: Probabilistic mapping of stimulation effects yielded a statistically significant cluster that was associated with a tremor improvement >50%. This cluster of optimal stimulation extended from the posterior subthalamic area to the ventralis intermedius nucleus and coincided with a normative structural connectivity-based cerebellothalamic tract (CTT). The combined features "distance between the stimulation volume and the significant cluster" and "CTT activation" were used as a predictor of tremor improvement. This correctly classified a >50% tremor improvement with a sensitivity of 89% and a specificity of 57%. INTERPRETATION: Our multicenter ET probabilistic stimulation map identified an area of optimal stimulation along the course of the CTT. The results of this study are mainly descriptive until confirmed in independent datasets, ideally through prospective testing. This target will be made openly available and may be used to guide surgical planning and for computer-assisted programming of DBS in the future. ANN NEUROL 2022;91:602-612.

Tractography-based versus anatomical landmark-based targeting in vALIC deep brain stimulation for refractory obsessive-compulsive disorder.

Deep brain stimulation (DBS) of the ventral anterior limb of the internal capsule (vALIC) is effective for refractory obsessive-compulsive disorder (OCD). Retrospective evaluation showed that stimulation closer to the supero-lateral branch of the medial forebrain bundle (slMFB), within the vALIC, was associated with better response to DBS. The present study is the first to compare outcomes of DBS targeted at the vALIC using anatomical landmarks and DBS with connectomic tractography-based targeting of the slMFB. We included 20 OCD-patients with anatomical landmark-based DBS of the vALIC that were propensity score matched to 20 patients with tractography-based targeting of electrodes in the slMFB. After one year, we compared severity of OCD, anxiety and depression symptoms, response rates, time to response, number of parameter adjustments, average current, medication usage and stimulation-related adverse effects. There was no difference in Y-BOCS decrease between patients with anatomical landmark-based and tractography-based DBS. Nine (45%) patients with anatomical landmark-based DBS and 13 (65%) patients with tractography-based DBS were responders (BF10 = 1.24). The course of depression and anxiety symptoms, time to response, number of stimulation adjustments or medication usage did not differ between groups. Patients with tractography-based DBS experienced fewer stimulation-related adverse effects than patients with anatomical landmark-based DBS (38 vs 58 transient and 1 vs. 17 lasting adverse effects; BF10 = 14.968). OCD symptoms in patients with anatomical landmark-based DBS of the vALIC and tractography-based DBS of the slMFB decrease equally, but patients with tractography-based DBS experience less adverse effects.

Directional versus ring-mode deep brain stimulation for Parkinson's disease: protocol of a multi-centre double-blind randomised crossover trial.

BACKGROUND: The effectiveness of Deep Brain Stimulation (DBS) therapy for Parkinson's disease can be limited by side-effects caused by electrical current spillover into structures adjacent to the target area. The objective of the STEEred versus RING-mode DBS for Parkinson's disease (STEERING) study is to investigate if directional DBS for Parkinson's disease results in a better clinical outcome when compared to ring-mode DBS. METHODS: The STEERING study is a prospective multi-centre double-blind randomised crossover trial. Inclusion criteria are Parkinson's disease, subthalamic nucleus DBS in a 'classic' ring-mode setting for a minimum of six months, and optimal ring-mode settings have been established. Participants are categorised into one of two subgroups according to their clinical response to the ring-mode settings as 'responders' (i.e., patient with a satisfactory effect of ring-mode DBS) or 'non-responder' (i.e., patient with a non-satisfactory effect of ring-mode DBS). A total of 64 responders and 38 non-responders will be included (total 102 patients). After an optimisation period in which an optimal directional setting is found, participants are randomised to first receive ring-mode DBS for 56 days (range 28-66) followed by directional DBS for 56 days (28-66) or vice-versa. The primary outcome is the difference between ring-mode DBS and directional DBS settings on the Movement Disorders Society Unified Parkinson's Disease Rating Scale - Motor Evaluation (MDS-UPDRS-ME) in the off-medication state. Secondary outcome measures consist of MDS-UPDRS-ME in the on-medication state, MDS-UPDRS Activities of Daily Living, MDS-UPDRS Motor Complications-Dyskinesia, disease related quality of life measured with the Parkinson's Disease Questionnaire 39, stimulation-induced side-effects, antiparkinsonian medication use, and DBS-parameters. Participants' therapy preference is measured at the end of the study. Outcomes will be analysed for both responder and non-responder groups, as well as for both groups pooled together. DISCUSSION: The STEERING trial will provide insights into whether or not directional DBS should be standardly used in all Parkinson's disease DBS patients or if directional DBS should only be used in a case-based approach. TRIAL REGISTRATION: This trial was registered on the Netherlands Trial Register, as trial NL6508 ( NTR6696 ) on June 23, 2017.

The Fast Gray Matter Acquisition T1 Inversion Recovery Sequence in Deep Brain Stimulation: Introducing the Rubral Wing for Dentato-Rubro-Thalamic Tract Depiction and Tremor Control.

BACKGROUND: The dentato-rubro-thalamic tract (DRT) is currently considered as a potential target in deep brain stimulation (DBS) for various types of tremor. However, tractography depiction can vary depending on the included brain regions. The fast gray matter acquisition T1 inversion recovery (FGATIR) sequence, with excellent delineation of gray and white matter, possibly provides anatomical identification of rubro-thalamic DRT fibers. OBJECTIVE: This study aimed to evaluate the FGATIR sequence by comparison with DRT depiction, electrode localization, and effectiveness of DBS therapy. MATERIALS AND METHODS: In patients with DBS therapy because of medication-refractory tremor, the FGATIR sequence was evaluated for depiction of the thalamus, red nucleus (RN), and rubro-thalamic connections. Deterministic tractography of the DRT, electrode localization, and tremor control were compared. The essential tremor rating scale was used to assess (hand) tremor. Tremor control was considered successful when complete tremor suppression (grade 0) or almost complete suppression (grade 1) was observed. RESULTS: In the postoperative phase, we evaluated 14 patients who underwent DRT-guided DBS: 12 patients with essential tremor, one with tremor-dominant Parkinson disease, and one with multiple sclerosis, representing 24 trajectories. Mean follow-up was 11.3 months (range 6-19 months). The FGATIR sequence provided a clear delineation of a hypointense white matter tract within the hyperintense thalamus. In coronal plane, this tract was most readily recognizable as a "rubral wing," with the round RN as base and lateral triangular convergence. The deterministic DRT depiction was consistently situated within the rubral wing. The number of active contacts located within the DRT (and rubral wing) was 22 (92%), of which 16 (73%) showed successful tremor control. CONCLUSIONS: The FGATIR sequence offers visualization of the rubro-thalamic connections that form the DRT, most readily recognizable as a "rubral wing" in coronal plane. This sequence contributes to tractographic depiction of DRT and provides a direct anatomical DBS target area for tremor control.

Utilizing 7-Tesla Subthalamic Nucleus Connectivity in Deep Brain Stimulation for Parkinson Disease.

BACKGROUND: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a highly effective surgical treatment for patients with advanced Parkinson disease (PD). Combining 7.0-Tesla (7T) T2- and diffusion-weighted imaging (DWI) sequences allows for selective segmenting of the motor part of the STN and, thus, for possible optimization of DBS. MATERIALS AND METHODS: 7T T2 and DWI sequences were obtained, and probabilistic segmentation of motor, associative, and limbic STN segments was performed. Left- and right-sided motor outcome (Movement Disorders Society Unified Parkinson's Disease Rating Scale) scores were used for evaluating the correspondence between the active electrode contacts in selectively segmented STN and the clinical DBS effect. The Bejjani line was reviewed for crossing of segments. RESULTS: A total of 50 STNs were segmented in 25 patients and proved highly feasible. Although the highest density of motor connections was situated in the dorsolateral STN for all patients, the exact partitioning of segments differed considerably. For all the active electrode contacts situated within the predominantly motor-connected segment of the STN, the average hemi-body Unified Parkinson's Disease Rating Scale motor improvement was 80%; outside this segment, it was 52% (p < 0.01). The Bejjani line was situated in the motor segment for 32 STNs. CONCLUSION: The implementation of 7T T2 and DWI segmentation of the STN in DBS for PD is feasible and offers insight into the location of the motor segment. Segmentation-guided electrode placement is likely to further improve motor response in DBS for PD. However, commercially available DBS software for postprocessing imaging would greatly facilitate widespread implementation.

The Medial Subthalamic Nucleus Border as a New Anatomical Reference in Stereotactic Neurosurgery for Parkinson's Disease.

INTRODUCTION: The intersection of Bejjani's line with the well-delineated medial subthalamic nucleus (STN) border on MRI has recently been proposed as an individualized reference in subthalamic deep brain stimulation (DBS) surgery for Parkinson's disease (PD). We, therefore, aimed to investigate the applicability across centers of the medial STN border as a patient-specific reference point in STN DBS for PD and explore anatomical variability between left and right mesencephalic area within patients. Furthermore, we aim to evaluate a recently defined theoretic stimulation "hotspot" in a different center. METHODS: Preoperative 3-Tesla T2 and susceptibility-weighted images (SWI) were used to identify the intersection of Bejjani's line with the medial STN border in left and right mesencephalic area. The average stereotactic coordinates of the center of stimulation relative to the medial STN border were compared with the predefined theoretic stimulation "hotspot." RESULTS: Fifty-four patients provided 108 stereotactic coordinates of medial STN borders on both sequences. Significant difference in means was found in the Y-(anteroposterior) and Z-(dorsoventral) directions (T2 vs. SWI; p < 0.001). Mean coordinates in the Y-(anteroposterior) direction differed significantly between left and right mesencephalic area (T2: p < 0.001; SWI: p = 0.021). Sixty-six DBS leads were placed in 36 patients that had finished stimulation programming, and the average stereotactic coordinates of the center of stimulation relative to the medial STN border on T2 sequences were 3.1 mm lateral, 0.7 mm anterior, and 1.8 mm superior, in proximity of the predefined theoretic stimulation "hotspot." CONCLUSION: The medial STN border is applicable across centers as a reference point for STN DBS surgery for PD and seems suitable in order to account for interindividual and intraindividual anatomical variability if one is aware of the discrepancies between T2-weighted imaging and SWI.

Relative Contribution of Magnetic Resonance Imaging, Microelectrode Recordings, and Awake Test Stimulation in Final Lead Placement during Deep Brain Stimulation Surgery of the Subthalamic Nucleus in Parkinson's Disease.

INTRODUCTION: For deep brain stimulation (DBS) surgery of the subthalamic nucleus (STN) in Parkinson's disease (PD), many centers employ visualization of the nucleus on magnetic resonance imaging (MRI), intraoperative microelectrode recordings (MER), and test stimulation in awake patients. The value of these steps is a subject for ongoing debate. In the current study, we determined the relative contribution of MRI targeting, multitrack MER, and awake test stimulation in final lead placement during STN DBS surgery for PD. METHODS: Data on PD patients undergoing MRI-targeted STN DBS surgery with three-channel MER and awake test stimulation between February 2010 and January 2014 were analyzed to determine in which MER trajectory final leads were implanted and why this tract was chosen. RESULTS: Seventy-six patients underwent implantation of 146 DBS leads. In 92% of the STN, the final leads were implanted in one of the three planned channels. In 6%, additional channels were needed. In 2%, surgery was aborted before final lead implantation due to anxiety or fatigue. The final leads were implanted in the channels with the longest STN MER signal trajectory in 60% of the STN (38% of the bilaterally implanted patients). This was the central channel containing the MRI target in 39% of the STN (18% bilaterally). The most frequently noted reasons why another channel than the central channel was chosen for final lead placement were (1) a lower threshold for side effects (54%) and (2) no or a too short trajectory of the STN MER signal (40%) in the central channel. The latter reason correlated with larger 2D (x and y) errors in our stereotactic method. CONCLUSIONS: STN DBS leads were often not implanted in the MRI-planned trajectory or in the trajectory with the longest STN MER signal. Thresholds for side effects during awake test stimulation were decisive for final target selection in the majority of patients.

Defining the Dorsal STN Border Using 7.0-T MRI: A Comparison to Microelectrode Recordings and Lower Field Strength MRI.

BACKGROUND: 7.0-T T2-weighted MRI offers excellent visibility of the subthalamic nucleus (STN), which is used as a target for deep brain stimulation (DBS) in Parkinson's disease (PD). A comparison of 7.0-T MRI to microelectrode recordings (MER) for STN border identification has not been performed. OBJECTIVE: To compare representation of STN borders on 7.0-T T2 MRI with the borders identified during MER in patients undergoing DBS for PD and to evaluate whether STN identification on 7.0-T T2 MRI leads to alterations in stereotactic target planning. DESIGN/METHODS: STN border identification was done using volumetric 7.0-T T2 MRI acquisitions. This was compared to the STN borders identified by MER. STN target planning was independently performed by 3 DBS surgeons on T2 imaging using 1.5-, 3.0-, and 7.0-T MRI. RESULTS: A total of 102 microelectrode tracks were evaluated in 19 patients. Identification of the dorsal STN border was well feasible on 7-T T2, whereas the ventral STN was un-distinguishable from the substantia nigra. The dorsal STN border on MRI was located more dorsal than MER in 73% of trajectories. The average distance from MRI to MER border was 0.9 mm (range -4.4 to +3.5 mm). STN target planning showed high correspondence between the 3 field strengths. CONCLUSION: 7.0-T T2 MRI offers the possibility of easy identification of the dorsal border of the STN. However, higher field strength MRI does not change the planning of the target. Compared to MER, the dorsal border on MRI was located more dorsal in the majority of cases, situating MER activity within STN representation.

Deep brain stimulation for Parkinson's disease: defining the optimal location within the subthalamic nucleus.

BACKGROUND: Individual motor improvement after deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson's disease (PD) varies considerably. Stereotactic targeting of the dorsolateral sensorimotor part of the STN is considered paramount for maximising effectiveness, but studies employing the midcommissural point (MCP) as anatomical reference failed to show correlation between DBS location and motor improvement. The medial border of the STN as reference may provide better insight in the relationship between DBS location and clinical outcome. METHODS: Motor improvement after 12 months of 65 STN DBS electrodes was categorised into non-responding, responding and optimally responding body-sides. Stereotactic coordinates of optimal electrode contacts relative to both medial STN border and MCP served to define theoretic DBS 'hotspots'. RESULTS: Using the medial STN border as reference, significant negative correlation (Pearson's correlation -0.52, P<0.01) was found between the Euclidean distance from the centre of stimulation to this DBS hotspot and motor improvement. This hotspot was located at 2.8 mm lateral, 1.7 mm anterior and 2.5 mm superior relative to the medial STN border. Using MCP as reference, no correlation was found. CONCLUSION: The medial STN border proved superior compared with MCP as anatomical reference for correlation of DBS location and motor improvement, and enabled defining an optimal DBS location within the nucleus. We therefore propose the medial STN border as a better individual reference point than the currently used MCP on preoperative stereotactic imaging, in order to obtain optimal and thus less variable motor improvement for individual patients with PD following STN DBS.

Accuracy of Microelectrode Trajectory Adjustments during DBS Assessed by Intraoperative CT.

BACKGROUND/AIMS: Microelectrode recording (MER)-guided deep brain stimulation (DBS) aims to place the DBS lead in the optimal electrophysiological target. When single-track MER or test stimulation yields suboptimal results, trajectory adjustments are made. The accuracy of these trajectory adjustments is unknown. Intraoperative computed tomography can visualize the microelectrode (ME) and verify ME adjustments. We aimed to determine the accuracy of ME movements in patients undergoing MER-guided DBS. METHODS: Coordinates following three methods of adjustment were compared: (1) those within the default "+" configuration of the ME holder; (2) those involving rotation of the default "+" to the "x" configuration; and (3) those involving head stage adjustments. Radial error and absolute differences between coordinates were determined. RESULTS: 87 ME movements in 59 patients were analyzed. Median (IQR) radial error was 0.59 (0.64) mm. Median (IQR) absolute x and y coordinate errors were 0.29 (0.52) and 0.38 (0.44) mm, respectively. Errors were largest after rotating the multielectrode holder to its "x"-shaped setup. CONCLUSION: ME trajectory adjustments can be made accurately. In a considerable number of cases, errors exceeding 1 mm were found. Adjustments from the "+" setup to the "x" setup are most prone to inaccuracies.

Electrode Penetration of the Caudate Nucleus in Deep Brain Stimulation Surgery for Parkinson's Disease.

OBJECTIVE: To evaluate the possible influence of electrode trajectories penetrating the caudate nucleus (CN) on cognitive outcomes in deep brain stimulation (DBS) surgery for Parkinson's disease (PD). BACKGROUND: It is currently unclear how mandatory CN avoidance during trajectory planning is. DESIGN/METHODS: Electrode trajectories were determined to be inside, outside, or in border region of the CN. Pre- and postoperative neuropsychological tests of each trajectory group were compared in order to evaluate possible differences in cognitive outcomes 12 months after bilateral STN DBS. RESULTS: One hundred six electrode tracks in 53 patients were evaluated. Bilateral penetration of the CN occurred in 15 (28%) patients, while unilateral penetration occurred in 28 (53%). In 19 (36%) patients tracks were located in the border region of the CN. There was no electrode penetration of the CN in 10 (19%) patients. No difference in cognitive outcomes was found between the different groups. CONCLUSION: Cognitive outcome was not influenced by DBS electrode tracks penetrating the CN. It is both feasible and sensible to avoid electrode tracks through the CN when possible, considering its function and anatomical position. However, penetration of the CN can be considered without major concerns regarding cognitive decline when this facilitates optimal trajectory planning due to specific individual anatomical variations.

Borders of STN determined by MRI versus the electrophysiological STN. A comparison using intraoperative CT.

BACKGROUND: It is unclear which magnetic resonance imaging (MRI) sequence most accurately corresponds with the electrophysiological subthalamic nucleus (STN) obtained during microelectrode recording (MER, MER-STN). CT/MRI fusion allows for comparison between MER-STN and the STN visualized on preoperative MRI (MRI-STN). OBJECTIVE: To compare dorsal and ventral STN borders as seen on 3-Tesla T2-weighted (T2) and susceptibility weighted images (SWI) with electrophysiological STN borders in deep brain stimulation (DBS) for Parkinson's disease (PD). METHODS: Intraoperative CT (iCT) was performed after each MER track. iCT images were merged with preoperative images using planning software. Dorsal and ventral borders of each track were determined and compared to MRI-STN borders. Differences between borders were calculated. RESULTS: A total of 125 tracks were evaluated in 45 patients. MER-STN started and ended more dorsally than respective dorsal and ventral MRI-STN borders. For dorsal borders, differences were 1.9 ± 1.4 mm (T2) and 2.5 ± 1.8 mm (SWI). For ventral borders, differences were 1.9 ± 1.6 mm (T2) and 2.1 ± 1.8 mm (SWI). CONCLUSIONS: Discrepancies were found comparing borders on T2 and SWI to the electrophysiological STN. The largest border differences were found using SWI. Border differences were considerably larger than errors associated with iCT and fusion techniques. A cautious approach should be taken when relying solely on MR imaging for delineation of both clinically relevant STN borders.

Accuracy of Intraoperative Computed Tomography during Deep Brain Stimulation Procedures: Comparison with Postoperative Magnetic Resonance Imaging.

OBJECTIVE: To determine the accuracy of intraoperative computed tomography (iCT) in localizing deep brain stimulation (DBS) electrodes by comparing this modality with postoperative magnetic resonance imaging (MRI). BACKGROUND: Optimal lead placement is a critical factor for the outcome of DBS procedures and preferably confirmed during surgery. iCT offers 3-dimensional verification of both microelectrode and lead location during DBS surgery. However, accurate electrode representation on iCT has not been extensively studied. METHODS: DBS surgery was performed using the Leksell stereotactic G frame. Stereotactic coordinates of 52 DBS leads were determined on both iCT and postoperative MRI and compared with intended final target coordinates. The resulting absolute differences in X (medial-lateral), Y (anterior-posterior), and Z (dorsal-ventral) coordinates (ΔX, ΔY, and ΔZ) for both modalities were then used to calculate the euclidean distance. RESULTS: Euclidean distances were 2.7 ± 1.1 and 2.5 ± 1.2 mm for MRI and iCT, respectively (p = 0.2). CONCLUSION: Postoperative MRI and iCT show equivalent DBS lead representation. Intraoperative localization of both microelectrode and DBS lead in stereotactic space enables direct adjustments. Verification of lead placement with postoperative MRI, considered to be the gold standard, is unnecessary.

Analysis of Stereotactic Accuracy in Patients Undergoing Deep Brain Stimulation Using Nexframe and the Leksell Frame.

OBJECTIVE: To determine and compare the accuracy of Nexframe and the Leksell stereotactic frame in deep brain stimulation (DBS) procedures. BACKGROUND: The 'frameless' Nexframe uses bone fiducials rather than a head-mounted frame, which offers potential benefits for both the patient and the surgical team. Accuracy of lead implantation and factors affecting this accuracy are of crucial importance but have not been extensively studied for the frameless system. DESIGN/METHODS: The location of 194 (Leksell frame, n = 116; Nexframe, n = 78) DBS leads was determined on postoperative MRI. Obtained stereotactic coordinates were compared with expected intraoperative target coordinates. Resulting absolute errors in the X (medial-lateral), Y (anterior-posterior), and Z (dorsal-ventral) coordinates (x0394;X, x0394;Y, and x0394;Z) were then used to calculate the vector error (VE). The vector error describes the total error in 3-D space and represents our main outcome measure. RESULTS: The vector error (mean ± SD) was 2.8 ± 1.3 for Nexframe and 2.5 ± 1.2 for the Leksell frame (p = 0.43). For Nexframe, absolute X, Y, and Z errors were 1.4 ± 1.3, 1.7 ± 1.2, and 1.0 ± 0.9 mm. For the Leksell frame, the absolute X, Y, and Z errors were 1.4 ± 1.0, 1.2 ± 1.0, and 1.3 ± 0.9 mm. On the anterior-posterior plane (Y coordinate), the Leksell frame was more accurate than Nexframe (p = 0.04). In contrast, Nexframe was more accurate on the dorsal-ventral plane (Z coordinate) (p = 0.04). There was no difference in accuracy between the two methods on the medial-lateral plane (X coordinate). CONCLUSION: This comparison of Nexframe and the Leksell frame shows that both techniques have equivalent overall 3-D accuracy.

7-Tesla Magnetic Resonance Imaging Scanning in Deep Brain Stimulation for Parkinson's Disease: Improving Visualization of the Dorsolateral Subthalamic Nucleus.

BACKGROUND: Identifying the dorsolateral subthalamic nucleus (STN) for deep brain stimulation (DBS) in Parkinson's disease (PD) can be challenging due to the size and double-oblique orientation. Since 2015 we implemented 7-Tesla T2 weighted magnetic resonance imaging (7 T T2) for improving visualization and targeting of the dorsolateral STN. We describe the changes in surgical planning and outcome since implementation of 7 T T2 for DBS in PD. METHODS: By comparing two cohorts of STN DBS patients in different time periods we evaluated the influence of 7 T T2 on STN target planning, the number of microelectrode recording (MER) trajectories, length of STN activity and the postoperative motor (UPDRS) improvement. RESULTS: From February 2007 to January 2014, 1.5 and 3-Tesla T2 guided STN DBS with 3 MER channels was performed in 76 PD patients. Average length of recorded STN activity in the definite electrode trajectory was 3.9 ± 1.5 mm. From January 2015 to January 2022 7 T T2 and MER-guided STN DBS was performed in 182 PD patients. Average length of recorded STN activity in the definite electrode trajectory was 5.1 ± 1.3 mm and used MER channels decreased from 3 to 1. Average UPDRS improvement was comparable. CONCLUSION: Implementation of 7 T T2 for STN DBS enabled a refinement in targeting. Combining classical DBS targeting with dorsolateral STN alignment may be used to determine the optimal trajectory. The improvement in dorsolateral STN visualization can be used for further target refinements, for example adding probabilistic subthalamic connectivity, to enhance clinical outcome of STN DBS.