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Background: Dentato-rubro-thalamic tract (DRT) deep brain stimulation (DBS) suppresses tremor in essential tremor (ET) patients. However, DRT depiction through tractography can vary depending on the included brain regions. Moreover, it is unclear which section of the DRT is optimal for DBS., Objective: To evaluate deterministic DRT tractography and tremor control in DBS for ET., Methods: After DBS surgery, DRT tractography was conducted in 37 trajectories (20 ET patients). Per trajectory, 5 different DRT depictions with various regions of interest (ROI) were constructed. Comparison resulted in a DRT depiction with highest correspondence to intraoperative tremor control. This DRT depiction was subsequently used for evaluation of short-term postoperative adverse and beneficial effects., Results: Postoperative optimized DRT tractography employing the ROI motor cortex, posterior subthalamic area (PSA), and ipsilateral superior cerebellar peduncle and dentate nucleus best corresponded with intraoperative trajectories (92%) and active DBS contacts (93%) showing optimal tremor control. DRT tractography employing a red nucleus or ventral intermediate nucleus of the thalamus (VIM) ROI often resulted in a more medial course. Optimal stimulation was located in the section between VIM and PSA., Conclusion: This optimized deterministic DRT tractography strongly correlates with optimal tremor control. This technique is readily implementable for prospective evaluation in DBS target planning for ET., (© Congress of Neurological Surgeons 2021.)

Background: Intraoperative cone-beam computed tomography (iCBCT) allows for rapid 3-dimensional imaging. However, it is currently unknown whether this imaging technique offers sufficient accuracy for stereotactic registration during deep brain stimulation (DBS) procedures., Objective: To determine the accuracy of iCBCT, with the O-arm O2 (Medtronic), for stereotactic registration by comparing this modality to stereotactic magnetic resonance imaging (MRI)., Methods: All DBS patients underwent a preoperative non-stereotactic 3 Tesla MRI, stereotactic 1.5 Tesla MRI, stereotactic O-arm iCBCT, postimplantation O-arm iCBCT, and postoperative conventional multidetector computed tomography (CT) scan. We compared stereotactic (X, Y, and Z) coordinates of the anterior commissure (AC), the posterior commissure (PC), and midline reference (MR) between stereotactic MRI and iCBCT. For localisation comparison of electrode contacts, stereotactic coordinates of electrode tips were compared between the postoperative multidetector CT and iCBCT., Results: A total of 20 patients were evaluated. The average absolute difference in stereotactic coordinates of AC, PC, and MR was 0.4 ± 0.4 mm for X, 0.4 ± 0.4 mm for Y, and 0.7 ± 0.5 mm for Z. The average absolute difference in X-, Y-, and Z-coordinates for electrode localisation (N = 34) was 0.3 ± 0.3 mm, 0.6 ± 0.3 mm, and 0.6 ± 0.6 mm. These differences were small enough not to be considered clinically relevant., Conclusion: Stereotactic MRI and O-arm iCBCT yield comparable coordinates in pre- and postoperative imaging. Differences found are below the threshold of clinical relevance. Intraoperative O-arm CBCT offers rapid stereotactic registration and evaluation of electrode placement. This increases patient comfort and neurosurgical workflow efficiency., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Background: Based on randomized controlled trials (RCTs), clinical guidelines for the treatment of space-occupying hemispheric infarct employ age (≤60 yr) and time elapsed since stroke onset (≤48 h) as decisive criteria whether to perform decompressive craniectomy (DC). However, only few patients in these RCTs underwent DC after 48 h., Objective: To study the association between the timing of DC and (un)favorable outcome in patients with space-occupying middle cerebral artery (MCA) infarct undergoing DC., Methods: We performed a single-center cohort study from 2007 to 2017. Unfavorable outcome at 1 yr was defined as a Glasgow outcome scale 1 to 3. Additionally, we systematically reviewed the literature up to November 2018, including studies reporting on the timing of DC and other predictors of outcome. We performed Firth penalized likelihood and random-effects meta-analysis with odds ratio (OR) on unfavorable outcome., Results: A total of 66 patients were enrolled. A total of 26 (39%) patients achieved favorable and 40 (61%) unfavorable outcomes (13 [20%] died). DC after 48 h since stroke diagnosis did not significantly increase the risk of unfavorable outcome (OR 0.8, 95% CI 0.3-2.3). Also, in the meta-analysis, DC after 48 h of stroke onset was not associated with a higher risk of unfavorable outcome (OR 1.11; 95% CI 0.89-1.38)., Conclusion: The outcome of DC performed after 48 h in patients with malignant MCA infarct was not worse than the outcome of DC performed within 48 h. Contrary to current guidelines, we, therefore, advocate not to set a restriction of ≤48 h on the time elapsed since stroke onset in the decision whether to perform DC., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Background: Ventral intermediate nucleus (VIM) deep brain stimulation (DBS) and posterior subthalamic area (PSA) DBS suppress tremor in essential tremor (ET) patients, but it is not clear which target is optimal. Aligning both targets in 1 surgical trajectory would facilitate exploring stimulation of either target in a single patient., Objective: To evaluate aligning VIM and PSA in 1 surgical trajectory for DBS in ET., Methods: Technical aspects of trajectories, intraoperative stimulation findings, final electrode placement, target used for chronic stimulation, and adverse and beneficial effects were evaluated., Results: In 17 patients representing 33 trajectories, we successfully aligned VIM and PSA targets in 26 trajectories. Trajectory distance between targets averaged 7.2 (range 6-10) mm. In all but 4 aligned trajectories, optimal intraoperative tremor suppression was obtained in the PSA. During follow-up, active electrode contacts were located in PSA in the majority of cases. Overall, successful tremor control was achieved in 69% of patients. Stimulation-induced dysarthria or gait ataxia occurred in, respectively, 56% and 44% of patients. Neither difference in tremor suppression or side effects was noted between aligned and nonaligned leads nor between the different locations of chronic stimulation., Conclusion: Alignment of VIM and PSA for DBS in ET is feasible and enables intraoperative exploration of both targets in 1 trajectory. This facilitates positioning of electrode contacts in both areas, where multiple effective points of stimulation can be found. In the majority of aligned leads, optimal intraoperative and chronic stimulation were located in the PSA.

Background: Susceptibility-weighted imaging (SWI) offers significantly improved visibility of the subthalamic nucleus (STN) compared with traditional T2-weighted imaging. However, it is unknown whether the representation of the nucleus on SWI corresponds to the neurophysiological location of the STN., Objective: To determine the correlation between the intraoperative electrophysiological activity of the STN and the representation of the nucleus on different magnetic resonance imaging (MRI) sequences used for deep brain stimulation target planning., Methods: At stereotactic target depth, microelectrode recordings (MERs) of typical STN neuronal activity were mapped on 3 different preoperative MRI sequences: 1.5-T SWI, 1.5-T T2-weighted, and 3-T T2-weighted MRI. For each MRI sequence, it was determined whether the MER signal was situated inside or outside the contour of the STN., Results: A total of 196 MER tracks in 34 patients were evaluated. In 165 tracks (84%), typical electrophysiological STN activity was measured. MER activity was situated more consistently inside hypointense STN contour representation on 1.5- and 3-T T2-weighted images compared with SWI (99% and 100% vs 79%, respectively). The 21% incongruence of electrophysiological STN activity outside the STN contour on SWI was seen almost exclusively in the anterior and lateral microelectrode channels., Conclusion: STN representation on SWI does not correspond to electrophysiological STN borders. SWI does not correctly display the lateral part of the STN. When aiming to target the superolateral sensorimotor part of the STN during deep brain stimulation surgery, SWI does not offer an advantage but a disadvantage compared with conventional T2. Future research is needed to determine whether these findings may also apply for high-field SWI.

Background and Importance: Deep brain stimulation (DBS) is an effective treatment for patients with refractory neuropsychiatric disorders. Along with symptom improvement, DBS may have concurrent behavioral effects that help to unravel the role of specific brain circuitries in complex human behavior., Clinical Presentation: This article reports on 2 patients with obsessive-compulsive disorder who received DBS targeted at the nucleus accumbens that resulted in a temporary change of accent and use of vocabulary., Conclusion: Changes in accent and speaking manners are most likely related to direct DBS stimulation effects of the electrode targeted at the nucleus accumbens. The shift in accent, resembling foreign accent syndrome after injuries in brain language centers, has not been reported before in the course of DBS. Induction of aggressive vocabulary may be related to transient hypomanic behavior after DBS.

Background: Displacement of deep brain stimulation (DBS) electrodes may occur after surgery, especially due to large subdural air collections, but other factors might contribute., Objective: To investigate factors potentially contributing to postoperative electrode displacement, in particular, different lead-anchoring techniques., Methods: We retrospectively analyzed 55 patients (106 electrodes) with Parkinson disease, dystonia, tremor, and obsessive-compulsive disorder in whom early postoperative and long-term follow-up computed tomography (CT) was performed. Electrodes were anchored with a titanium microplate or with a commercially available plastic cap system. Two independent examiners determined the stereotactic coordinates of the deepest DBS contact on early postoperative and long-term follow-up CT. The influence of age, surgery duration, subdural air volume, use of microrecordings, fixation method, follow-up time, and side operated on first was assessed., Results: Subdural air collections measured on average 4.3 ± 6.2 cm. Three-dimensional (3-D) electrode displacement and displacement in the X, Y, and Z axes significantly correlated only with the anchoring method, with larger displacement for microplate-anchored electrodes. The average 3-D displacement for microplate-anchored electrodes was 2.3 ± 2.0 mm vs 1.5 ± 0.6 mm for electrodes anchored with the plastic cap (P = .030). Fifty percent of the microplate-anchored electrodes showed 2-mm or greater (potentially relevant) 3-D displacement vs only 25% of the plastic cap-anchored electrodes (P < .01)., Conclusion: The commercially available plastic cap system is more efficient in preventing postoperative DBS electrode displacement than titanium microplates. A reliability analysis of the electrode fixation is warranted when alternative anchoring methods are used.

Background and Importance: To report the clinical presentation and management of an intracranial frontoparietal malignant peripheral nerve sheath tumor (MPNST) and its recurrence in a 6-year-old girl, along with a systematic review of the literature., Clinical Presentation: A previously healthy 6-year-old girl presented with severe signs of increased intracranial pressure. Magnetic resonance imaging (MRI) revealed a large heterogeneously enhancing mass at the right frontoparietal convexity. The tumor was completely removed, the histological diagnosis was MPNST, and the patient underwent adjuvant radio- and chemotherapy. Fifteen months later, MRI revealed a small local recurrence. After upfront chemotherapy, the recurrence was removed in a radical, ie, true oncological, neuronavigationally guided, en bloc resection, including approximately 1 cm surrounding gray and white matter and overlying dura mater. Neuropathological examination revealed tumor-free margins. The patient again received adjuvant chemotherapy. Four years after diagnosis and 20 months after cessation of adjuvant therapy, there are no signs of tumor recurrence. The literature search resulted in 17 cases of intracranial MPNSTs not associated with cranial nerves. Despite macroscopically complete resection in many cases and adjuvant radio- and chemotherapy, overall survival was poor, with only 5 patients still alive upon publication (including the current patient)., Conclusion: Intracranial MPNSTs not associated with cranial nerves are extremely rare and highly malignant tumors with poor overall survival, probably because of infiltrating growth into surrounding brain tissue. We therefore advocate consideration of nonconventional true oncological en bloc resection when approaching this rare tumor or its recurrence.

Background: Accurate electrode position is important for the efficacy of deep brain stimulation (DBS). Several reports revealed errors during stereotactic surgery due to cerebrospinal fluid (CSF) loss and subdural air invasion. Because subdural air resolves in the weeks after surgery and the brain returns to its original position, DBS electrodes may become displaced postoperatively., Objective: To quantitatively assess postoperative DBS electrode displacement in relation to subdural air invasion., Methods: We retrospectively analyzed 14 patients with advanced Parkinson disease and subthalamic nucleus DBS electrodes that underwent immediate postoperative frame-based stereotactic computer tomography (CT) and repeated CT after longer follow-up. We performed volumetric measurements of postoperative subdural air collections on both sides of the brain and determined stereotactic coordinates of the deepest DBS contact on the direct postoperative and follow-up CT., Results: Subdural air collections measured on average 17+/-24 cm. Consequently, the frontal cortex shifted posteriorly. On follow-up imaging after 16+/-8 months, air collections had resolved and the frontal cortex had returned to its original position, causing anterior curving of the electrodes. The electrodes moved on average 3.3+/-2.5 mm upward along the trajectory. This displacement significantly correlated with the amount of postoperative subdural air., Conclusion: Considerable displacement of DBS electrodes may occur in the weeks following surgery, especially in cases with large postoperative subdural air volumes. Postoperative documentation of electrode localization should therefore be repeated after longer follow-up.