Search

Background: Percutaneous rhizotomy of the Gasserian ganglion for trigeminal neuralgia is an effective therapeutic procedure. Yet, landmark-guided cannulation of the foramen ovale is manually challenging and difficult to learn., Objective: To overcome these limitations, we assessed the feasibility and accuracy of an augmented reality (AR)-guided puncture of the foramen ovale., Methods: A head phantom with soft tissue structures of the facial area was built. A three-dimensional (3D)-dataset of the phantom was generated using a stereotactic planning workstation. An optimal trajectory to the foramen ovale was created and then transferred to an AR headset. A total of 2 neurosurgeons and 2 neuroradiologists independently performed 8 AR-guided and 8 landmark-guided cannulations of the foramen ovale, respectively. For each AR-guided cannulation, the hologram was manually aligned with the phantom. Accuracy of the cannulation was evaluated using the Euclidean distance to the target point as well as the lateral deviation of the achieved trajectory from the planned trajectory at target point level., Results: With the help of AR guidance, a successful cannulation of the foramen ovale was achieved in 90.6% compared to the purely landmark-based method with 18.8%. Euclidean distance and lateral deviation were significantly lower with AR guidance than landmark guidance (P < .01)., Conclusion: AR greatly improved accuracy of simulated percutaneous rhizotomy of the Gasserian ganglion., (© Congress of Neurological Surgeons 2021.)

Background: Automatic segmentation is gaining relevancy in image-based targeting of neural structures., Objective: To evaluate its feasibility, we retrospectively analyzed the concordance of magnetic resonance imaging (MRI)-based automatic segmentation of the subthalamic nucleus (STN) and intraoperative microelectrode recordings (MERs)., Methods: Electrodes (n = 60) for deep brain stimulation were implanted in the STN of patients (n = 30; median age 57 yr) with Parkinson disease (n = 29) or rapid-onset dystonia parkinsonism (n = 1). Elements (Brainlab, Munich, Germany) were used to segment the STN, using 2 volumetric T1 (±contrast) and volumetric T2 images as input. The stereotactic computed tomography was coregistered with the imaging, and the original stereotactic coordinates were imported. MERs (0.5-1 mm steps) along the anterior, central, and lateral trajectories were used to determine differences between the image-segmented STN boundary and MER-based STN entry and exit., Results: Of 175 trajectories, 105 penetrated or touched (≤0.7 mm) the STN. The overall median deviation between the segmented STN boundary and electrophysiological recordings was 1.1 mm for MER-based STN entry and 2.0 mm for STN exit. Regarding the entry point of the STN, there was no statistically significant difference between MRI-based automatic segmentation and the electrophysiological trajectories analyzed with intraoperative MER. The exit point was significantly different between both methods in the central and lateral trajectories., Conclusion: MRI-based automatic segmentation of the STN is a viable, patient-specific targeting approach that can be used alongside traditional targeting methods in deep brain stimulation to support preoperative planning and visualization of target structures and aid postoperative optimization of programming., (Copyright © 2019 by the Congress of Neurological Surgeons.)

Background: The Medtronic Registry for Epilepsy (MORE; Medtronic Inc, Dublin, Ireland) is an open label observational study evaluating the long-term effectiveness, safety, and performance of deep brain stimulation (DBS) of the anterior nucleus of thalamus (ANT) for the treatment of refractory epilepsy., Objective: To compare the difference in success rate of placing contacts at ANT-target region (ANT-TR) between transventricular (TV) and extraventricular (EV) lead trajectories in 73 ANT-DBS implants in 17 European centers participating in the MORE registry., Methods: The success rate of placing contacts at ANT-TR was evaluated using a screening method combining both individual patient imaging information and stereotactic atlas information to identify contacts at ANT-TR., Results: EV lead trajectory was used in 53% of the trajectories. Approximately, 90% of the TV lead trajectories had at least 1 contact at ANT-TR, vs only 71% of the EV lead trajectories. The success rate for placing at least 1 contact at ANT-TR bilaterally was 84% for TV implants and 58% for EV implants (P < .05; Fisher's exact). No intracranial bleedings were observed, but 1 cortical infarct was reported following EV lead trajectory., Conclusion: The results of this registry support the use of TV lead trajectories for ANT-DBS as they have a higher probability in placing contacts at ANT-TR, without appearing to compromise procedural safety. Follow-up data collection is continuing in the MORE registry. These data will provide outcomes associated with TV and EV trajectories.

Background: Cerebral vasospasm leading to delayed cerebral infarction (DCI) is a central source of poor outcome in patients with aneurysmal subarachnoid hemorrhage (aSAH). Current treatments of cerebral vasospasm are insufficient. Cisternal blood clearance is a promising treatment option. However, a generally applicable, safe, and effective method to access the cisterns of the brain is lacking., Objective: To report on stereotactic catheter ventriculocisternostomy (STX-VCS) as a method to access the cisterns of the brain for clearance of subarachnoid hemorrhage in patients with aSAH and coiled aneurysms., Methods: In 9 aSAH patients at high risk for DCI (Hunt and Hess grade ≥3, modified Fisher grade ≥3), access to the basal cisterns of the brain was created by STX-VCS. Fibrinolytic and/or spasmolytic lavage therapy was administered., Results: STX-VCS was feasible and safe in all patients. Subarachnoid blood was rapidly cleared by irrigation with urokinase. Vasospasm occurred in 2 patients and was interrupted by irrigation with nimodipine. There was 1 fatality due to pneumogenic sepsis. Minor DCI occurred in 1 patient. Eight survived without DCI and are independent (modified Rankin score [mRS] ≤ 3) at 6 mo after aSAH., Conclusion: STX-VCS allows for rapid clearance of subarachnoid hemorrhage in patients with coiled aneurysms., (Copyright © 2017 by the Congress of Neurological Surgeons)

Background: Deep brain stimulation alleviates tremor of various origins. Several regions like the ventralis intermediate nucleus of thalamus, the caudal zona incerta, and the posterior subthalamic region are generally targeted. Previous work with fiber tractography has shown the involvement of the cerebello-thalamo-cortical network in tremor control., Objective: To report the results of a prospective trial in a group of patients with tremor who underwent post hoc tractographic analysis after treatment with traditional thalamic deep brain stimulation., Methods: A total of 11 patients (aged 64 ± 17 years, 6 male) were enrolled (essential tremor [6], Parkinson tremor [3], and myoclonic tremor in myoclonus dystonia [2]). Patients received 1 (3 patients), 2 (7 patients), or 3 (1 patient) quadripolar electrodes. A 32-direction diffusion tensor magnetic resonance imaging sequence was acquired preoperatively. Tractography was processed postoperatively for evaluation and the dentato-rubro-thalamic tract (DRT) was individually tracked. Electrode positions were determined with helical computed tomography. Electric fields (EFs) were simulated according to individual stimulation parameters in a standardized atlas brain space (ICBM-MNI 152)., Results: Tremor was reduced in all patients (69.4% mean) on the global (bilateral) tremor score. Effective contacts were located inside or in proximity to the DRT. In moderate tremor reduction (2 patients), the EFs were centered on its anterior border. In good and excellent tremor reduction (9 patients), EFs focused on its center., Conclusion: Deep brain stimulation of the cerebello-thalamo-cortical network reduces tremor. The DRT connects 3 traditional target regions for deep brain stimulation in tremor disease. Tractography techniques can be used to directly visualize the DRT and, therefore, optimize target definition in individual patients.

Background: Deep brain stimulation (DBS) has been proven to alleviate tremor of various origins. Distinct regions have been targeted. One explanation for good clinical tremor control might be the involvement of the dentatorubrothalamic tract (DRT) as has been suggested in superficial (thalamic) and inferior (posterior subthalamic) target regions. Beyond a correlation with atlas data and the postmortem evaluation of patients treated with lesion surgery, proof for the involvement of DRT in tremor reduction in the living, the scope of this work, is elusive., Objective: To report a case of unilateral refractory tremor in tremor-dominant Parkinson disease treated with thalamic DBS., Methods: Preoperative diffusion tensor imaging (DTI) was performed. Correlation with individual DBS electrode contact locations was obtained through postoperative fusion of helical computed tomography (CT) data with DTI fiber tracking., Results: Tremor was alleviated effectively. An evaluation of the active electrode contact position revealed clear involvement of the DRT in tremor control. A closer evaluation of clinical effects and side effects revealed a highly detailed individual fiber map of the subthalamic region with DTI fiber tracking., Conclusion: This is the first time the involvement of the DRT in tremor reduction through DBS has been shown in the living. The combination of DTI with postoperative CT and the evaluation of the electrophysiological environment of distinct electrode contacts led to an individual detailed fiber map and might be extrapolated to refined DTI-based targeting strategies in the future. Data acquisition for a larger study group is the topic of our ongoing research.

Objective: Hypomania accounts for approximately 4% to 13% of psychotropic adverse events during subthalamic nucleus (STN) deep brain stimulation (DBS) for Parkinson's disease. Diffusion of current into the inferior and medial "limbic" STN is often reported to be the cause. We suggest a different explanation, in which the coactivation of the medial forebrain bundle (MFB), outside the STN, leads to hypomania during STN DBS., Methods: Six patients with advanced Parkinson's disease (age, 54 +/- 11 years) underwent bilateral STN DBS surgery. Preoperative diffusion tensor imaging scans for fiber tracking of the MFB were conducted on a 3T magnetic resonance imaging scanner. After implantation, the electrode positions were determined with computed tomography and integrated in a diffusion tensor imaging software environment., Results: The medial STN was shown to send tributaries to the MFB using it as a pathway to connect to the reward circuitry. One patient, who had a transient, stimulation-induced acute hypomanic episode, showed a direct contact between 1 active electrode contact and these putative limbic STN tributaries to the MFB unilaterally on the left. In 5 asymptomatic patients, the active contacts were between 2.9 and 7.5 mm distant from the MFB or its limbic STN tributaries., Conclusion: We hypothesize that STN DBS-induced reversible acute hypomania might be elicited by inadvertent and unilateral coactivation of putative limbic STN tributaries to the MFB. These findings may provide insight into the neural pathways of hypomania and may facilitate future investigations of the pathophysiology of mood disorders.

Objective: We present a technique that allows intraoperative display of brain shift and its effects on fiber tracts., Methods: Three patients had intracranial lesions (one malignant glioma, one metastasis, and one cavernoma) in contact with either the corticospinal or the geniculostriate tract that were removed microneurosurgically. Preoperatively, magnetic resonance diffusion-weighted imaging (DWI) was performed to visualize the fiber tract at risk. DWI data were fused with those obtained from anatomic T1-weighted magnetic resonance imaging. A single-rack three-dimensional ultrasound neuronavigation system, which simultaneously displays the MRI scan and the corresponding ultrasound image, was used intraoperatively for 1) navigation; 2) definition of fixed and potentially shifting ultrasound landmarks near the fiber tract; and 3) sequential image updating at different steps of resection. The result was time-dependent brain deformation data. With a standard personal computer equipped with standard image software, the brain shift-associated fiber tract deformation was assessed by use of sequential landmark registration. After surgery, DWI was performed to confirm the predicted fiber tract deformation., Results: The lesions were removed without morbidity. Comparison of three-dimensional ultrasound with DWI and T1-weighted magnetic resonance imaging data allowed us to define fixed and potentially shifting landmarks close to the respective fiber tract. Postoperative DWI confirmed that the actual fiber tract position at the conclusion of surgery corresponded to the sonographically predicted fiber tract position., Conclusion: By definition and sequential intraoperative registration of ultrasound landmarks near the fiber tract, brain shift-associated deformation of a tract that is not visible sonographically can be assessed correctly. This approach seems to help identify and avoid eloquent brain areas during intracranial surgery.

Objective: To integrate spatial three-dimensional information concerning the pyramidal tracts into a customized system for frameless neuronavigation during brain tumor surgery., Methods: Four consecutive patients with intracranial tumors in eloquent areas underwent diffusion-weighted and anatomic magnetic resonance imaging studies within 48 hours before surgery. Diffusion-weighted datasets were merged with anatomic data for navigation purposes. The pyramidal tracts were segmented and reconstructed for three-dimensional visualization. The reconstruction results, together with the fused-image dataset, were available during surgery in the environment of a customized neuronavigation system., Results: In all four patients, the combination of reconstructed data and fused images was a helpful additional source of information concerning the tumor seat and topographical interaction with the pyramidal tract. In two patients, intraoperative motor cortex stimulation verified the tumor seat with regard to the precentral gyrus., Conclusion: Diffusion-weighted magnetic resonance imaging allows individual estimation of large fiber tracts applicable as important information in intraoperative neuronavigation and in planning brain tumor resection. A three-dimensional representation of fibers associated with the pyramidal tract during brain tumor surgery is feasible with the presented technique and is a helpful adjunct for the neurosurgeon. The main drawbacks include the length of time required for the segmentation procedure, the lack of direct intraoperative control of the pyramidal tract position, and brain shift. However, mapping of large fiber tracts and its intraoperative use for neuronavigation have the potential to increase the safety of neurosurgical procedures and to reduce surgical morbidity.