Gamma Knife central lateral thalamotomy for the treatment of neuropathic pain

J Neurosurg 135:228–236, 2021

The goal of this study was to assess the safety and efficacy of stereotactic central lateral thalamotomy with Gamma Knife radiosurgery in patients with neuropathic pain.

METHODS Clinical and radiosurgical data were prospectively collected and analyzed in patients with neuropathic pain who underwent Gamma Knife central lateral thalamotomy. The safety and efficacy of the lesioning procedure were evaluated by neurological examination and standardized scales for pain intensity and health-related quality of life. Visual analog scale (VAS) for pain, McGill Pain Questionnaire (MPQ), EuroQol–5 dimensions (EQ-5D), and the 36-Item Short Form Health Survey, version 2 (SF-36v2) were measured during baseline and postoperative follow-up evaluations at 3, 6, 12, 24, and 36 months.

RESULTS Eight patients with neuropathic pain underwent Gamma Knife central lateral thalamotomy. Four patients suffered from trigeminal deafferentation pain, 2 from brachial plexus injury, 1 from central poststroke facial neuropathic pain, and 1 from postherpetic neuralgia. No lesioning-related adverse effect was recorded during the follow-up periods. All patients had pain reduction following thalamotomy. The mean follow-up time was 24 months. At the last follow-up visits, 5 patients reported ≥ 50% VAS pain reduction. The overall mean VAS pain score was 9.4 (range 8–10) before radiosurgery. After 1 year, the mean VAS pain score decreased significantly, from 9.4 (range 8–10) to 5.5 (mean -41.33%, p = 0.01). MPQ scores significantly decreased (mean -22.18%, p = 0.014). Statistically significant improvements of the SF-36v2 quality of life survey (mean +48.16%, p = 0.012) and EQ-5D (+45.16%, p = 0.012) were observed. At 2 years after radiosurgery, the VAS pain score remained significantly reduced to a mean value of 5.5 (p = 0.027). Statistically significant improvements were also observed for the MPQ (mean -16.05%, p = 0.034); the EQ-5D (mean +35.48%, p = 0.028); and the SF-36v2 (mean +35.84%, p = 0.043). At the last follow-up visits, pain had recurred in 2 patients, who were suffering from central poststroke neuropathic pain and brachial plexus injury, respectively.

CONCLUSIONS Safe, nonpharmacological therapies are imperative for the management of refectory chronic pain conditions. The present series demonstrates that Gamma Knife central lateral thalamotomy is safe and potentially effective in the long term for relieving chronic neuropathic pain refractory to pharmacotherapy and for restoring quality of life.


Ultrasound Ablation in Neurosurgery: Current Clinical Applications and Future Perspectives

Neurosurgery 87:1–10, 2020

The concept of focusing high-intensity ultrasound beams for the purpose of cerebral ablation has interested neurosurgeons for more than 70 yr. However, the need for a craniectomy or a cranial acoustic window hindered the clinical diffusion of this technique.

Recent technological advances, including the development of phased-array transducers and magnetic resonance imaging technology, have rekindled the interest in ultrasound for ablative brain surgery and have led to the development of the transcranial magnetic resonance-guided focused ultrasound (MRgFUS) thermal ablation procedure. In the last decade, this method has become increasingly popular, and its clinical applications are broadening.

Despite the demonstrated efficacy of MRgFUS, transcranial thermal ablation using ultrasound is limited in that it can target exclusively the central region of the brain where the multiple acoustic beams are most optimally focused. On the contrary, lesioning of the cortex, the superficial subcortical areas, and regions close to the skull base is not possible with the limited treatment envelope of current phased-array transducers.

Therefore, new ultrasound ablative techniques, which are not based on thermal mechanisms, have been developed and tested in experimental settings. This review describes the mechanisms by which these novel, nonthermal ablative techniques are based and also presents the current clinical applications of MRgFUS thermal ablation.

Probabilistic versus deterministic tractography for delineation of the cortico-subthalamic hyperdirect pathway in patients with Parkinson disease selected for deep brain stimulation

J Neurosurg 126:1657–1668, 2017

Diffusion-weighted MRI (DWI) and tractography allows noninvasive mapping of the structural connections of the brain, and may provide important information for neurosurgical planning. The hyperdirect pathway, connecting the subthalamic nucleus (STN) with the motor cortex, is assumed to play a key role in mediating the effects of deep brain stimulation (DBS), which is an effective but poorly understood treatment for Parkinson disease. This study aimed to apply recent methodological advances in DWI acquisition and analysis to the delineation of the hyperdirect pathway in patients with Parkinson disease selected for surgery.

METHODS High spatial and angular resolution DWI data were acquired preoperatively from 5 patients with Parkinson disease undergoing DBS. The authors compared the delineated hyperdirect pathways and associated STN target maps generated by 2 different tractography methods: a tensor-based deterministic method, typically available in clinical settings, and an advanced probabilistic method based on constrained spherical deconvolution. In addition, 10 highresolution data sets with the same scanning parameters were acquired from a healthy control participant to assess the robustness of the tractography results.

RESULTS Both tractography approaches identified connections between the ipsilateral motor cortex and the STN. However, the 2 methods provided substantially different target regions in the STN, with the target center of gravity differing by > 1.4 mm on average. The probabilistic method (based on constrained spherical deconvolution) plausibly reconstructed a continuous set of connections from the motor cortex, terminating in the dorsolateral region of the STN. In contrast, the tensor-based method reconstructed a comparatively sparser and more variable subset of connections. Furthermore, across the control scans, the probabilistic method identified considerably more consistent targeting regions within the STN compared with the deterministic tensor-based method, which demonstrated a 1.9–2.4 times higher variation.

CONCLUSIONS These data provide a strong impetus for the use of a robust probabilistic tractography framework based on constrained spherical deconvolution, or similar advanced DWI models, in clinical settings. The inherent limitations and demonstrated inaccuracy of the tensor-based method leave it questionable for use in high-precision stereotactic DBS surgery. The authors have also described a straightforward method for importing tractography-derived information into any clinical neuronavigation system, based on the generation of track-density images.

Electrophysiological validation of STN-SNr boundary depicted by susceptibility-weighted MRI

Electrophysiological validation of STN-SNr boundary depicted by susceptibility-weighted MRI

Acta Neurochir (2015) 157:2129–2134

Direct targeting of subthalamic nucleus (STN) without secondary electrophysiological verification during deep brain stimulation (DBS) is replacing atlas-based indirect targeting techniques. Recent groups have reported increased contrast and better delineation of STN and substantia nigra (SNr) in susceptibility-weighted imaging protocols (SWI). We aim to validate the STN-SNr boundary seen in MRISWI by correlating with intraoperative microelectrode recordings (MER) as a part of developing a multi-contrast DBSMRI planning protocol.

Methods Prospective service evaluation involving electrophysiological verification by correlation of MER trajectory and STN-SNr boundary seen in SWI in seven consecutive patients undergoing DBS surgery were analyzed. The angle of inclination of the STN-SNr boundary and DBS trajectory in the coronal plane were calculated. Considering 4-mm dispersion of a coronal 3 MER array, we predicted, measured, and correlated the depths at which each electrode engaged the boundary.

Results All central microelectrodes identified the STN-SNr boundary within 1 mm of the predicted depth with 100 % accuracy. Ninety percent of the lateral MER identified the STN-SNr boundary as predicted from SWI and angle of the encounter of the MER front.

Conclusions The study demonstrates that STN morphology can be depicted using SWI MRI and coincides reliably with the electrophysiological MER boundary. Thus, this imaging modality can be used to refine STN direct targeting protocols in DBS surgery for PD.

Postoperative Displacement of Deep Brain Stimulation Electrodes Related to Lead-Anchoring Technique

Postoperative Displacement of Deep Brain Stimulation Electrodes Related to Lead-Anchoring Technique-1

Neurosurgery 73:681–688, 2013

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 4.36±6.2 cm3. 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.

Accuracy of Frame-Based Stereotactic Magnetic Resonance Imaging vs Frame-Based Stereotactic Head Computed Tomography Fused With Recent Magnetic Resonance Imaging for Postimplantation Deep Brain Stimulator Lead Localization

Neurosurgery 69:1299–1306, 2011 DOI: 10.1227/NEU.0b013e31822b7069

Introduction of the portable intraoperative CT scanner provides for a precise and cost-effective way of fusing head CT images with high-tesla MRI for the exquisite definition of soft tissue needed for stereotactic targeting.

OBJECTIVE: To evaluate the accuracy of stereotactic electrode placement in patients undergoing deep brain stimulation (DBS) by comparing frame-based postimplantation intraoperative CT (iCT) images fused to a recent 3T-MRI with frame-based postimplantation intraoperative MRI (iMRI) alone.

METHODS: Frame-based DBS surgeries of 46 targets performed from February 8, 2007 to April 28, 2008 in 26 patients with the use of immediate postimplantation iMRI for target localization were compared with frame-based immediate postimplantation iCT fused with a recent 3T brain MRI for DBS localization of 50 targets performed from August 13, 2008 to February 18, 2010 in 26 patients. Pre- and postoperative mid anterior commissure-posterior commissure line coordinates and XYZ coordinates for preoperatively calculated DBS targets (intended target) and for the permanent DBS lead tips were determined. The differences between preoperative DBS target and postoperative permanent DBS lead-tip coordinates based on postimplantation intraoperative MRI for the MRI-alone group and based on postimplantation intraoperative CT fused to recent preoperative MRI in the CTMRI group were measured. The t test and Yuen test were used for comparison.

RESULTS: No statistically significant differences were found between the 2 groups when comparing the pre- and postperative changes in mid anterior commissure-posterior commissure line coordinates and XYZ coordinates.

CONCLUSION: Postimplantation DBS lead localization and therefore targeting accuracy was not significantly different between frame-based stereotactic 1.5T-MRI and framebased stereotactic head CT fused with recent 3T-MRI.

Fiducial Registration With Spoiled Gradient-Echo Magnetic Resonance Imaging Enhances the Accuracy of Subthalamic Nucleus Targeting

Neurosurgery 69:870–875, 2011 DOI: 10.1227/NEU.0b013e318222ae33

A variety of imaging strategies may be used to derive reliable stereotactic coordinates when performing deep brain stimulation lead implants. No single technique has yet proved optimal.

OBJECTIVE: To compare the relative accuracy of stereotactic coordinates for the subthalamic nucleus (STN) derived either from fast spin echo/inversion recovery (FSE/IR) magnetic resonance imaging MRI alone (group 1) or FSE/IR in conjunction with T1- weighted spoiled gradient-echo MRI (group 2).

METHODS: A retrospective analysis of 145 consecutive STN deep brain stimulation lead placements (group 1, n = 72; group 2, n = 73) was performed in 81 Parkinson disease patients by 1 surgical team. From the operative reports, we recorded the number of microelectrode recording trajectories required to localize the desired STN target and the span of STN traversed along the implantation trajectory. In addition, we calculated the 3-dimensional vector difference between the initial MRI-derived coordinates and the final physiologically refined coordinates.

RESULTS: The proportion of implants completed with just 1 microelectrode recording trajectory was greater (81% vs 58%; P < .001) and the 3-dimensional vector difference between the anatomically selected target and the microelectrode recording–refined target was smaller (0.6 ± 1.2 vs 0.9 ± 1.3; P = .04) in group 2 than in group 1. At the same time, the mean expanse of STN recorded along the implantation trajectory was 8% greater in group 2 (4.8 ± 0.6 vs 5.2 ± 0.6 mm; P < .001).

CONCLUSION: A combination of stereotactic FSE/IR and spoiled gradient-echo MRI yields more accurate coordinates for the STN than FSE/IR MRI alone.

Transgressing the Ventricular Wall During Subthalamic Deep Brain Stimulation Surgery for Parkinson Disease Increases the Risk of Adverse Neurological Sequelae

Neurosurgery 69:294–300, 2011 DOI: 10.1227/NEU.0b013e318214abda

Deep brain stimulation (DBS) at the subthalamic nucleus (STN) is an effective treatment for the motor manifestations of advanced medically refractory Parkinson disease. Because of the medial location of the target, surgical trajectories to the STN may violate the ipsilateral lateral ventricle.

OBJECTIVE: To determine whether violating the ventricle during STN DBS surgery is associated with postoperative confusion.

METHODS: A retrospective chart review of all STN implantation procedures for Parkinson disease performed by 1 surgeon between January 2005 and September 2008 was performed. Postoperative magnetic resonance imaging was performed in all cases, and each scan was reviewed for evidence of ventricular wall violation. All charts were reviewed for postoperative confusion and/or increased length of hospital stay.

RESULTS: A total of 145 leads were implanted in 81 patients over 102 admissions. Fortythree patients underwent contemporaneous bilateral lead implantation; 23 underwent unilateral implantation; and 18 underwent staged bilateral implantation. The cases of 8 patients were complicated by postoperative confusion and increased length of stay. Sixteen magnetic resonance imaging scans demonstrated evidence of ventricular wall violation including all 8 patients with postoperative confusion. The relative risk of having postoperative confusion after traversing the ventricle is 87 (P , .001).

CONCLUSION: Violating the ventricular system during STN DBS surgery correlated significantly with postoperative altered mental status and subsequent increased length of hospital stay. This finding may explain why cognitive complications are observed more frequently in Parkinson disease patients undergoing DBS at the STN compared with the internal globus pallidus.

Stereotactic versus endoscopic surgery in periventricular lesions

Acta Neurochir (2011) 153:517–526.DOI 10.1007/s00701-010-0933-x

Endoscopic and stereotactic surgery have gained widespread acceptance as minimally invasive tools for the diagnosis of intracerebral pathologies. We investigated the specific advantages and disadvantages of each technique in the assessment of periventricular lesions.

Method This study included a retrospective series of 70 patients with periventricular lesions. Endoscopic surgery was performed in 17 patients (mean age, 37 years; range, 4 months–78 years) and stereotactic biopsy in 55 patients (mean age, 63 years; range, 23–80 years), including two patients who underwent both procedures.

Results Hydrocephalus was present in 13/17 patients in the endoscopic group (77%) and in 11/55 patients in the stereotactic group (20%). Diagnosis was achieved in all patients in the endoscopic group and in all but one patient in the stereotactic group, in whom histological diagnosis was obtained by endoscopic biopsy during a second operation. In the endoscopic group, additional procedures performed included ventriculostomy (2/17), cyst fenestration (3/17), endoscopic shunt revision (3/17) and placement of Rickham reservoirs or external cerebrospinal fluid drains (6/17). Adverse events occurred in one patient after endoscopy (chronic subdural hematoma) and in two patients after stereotactic surgery (one mild hemiparesis and one transitory paresis of the contralateral leg).

Conclusions Endoscopic and stereotactic surgery have distinct advantages and disadvantages in approaching periventricular lesions. The advantages of endoscopy encompass the possibility to perform additional surgical procedures during the same session (e.g. tumour reduction, third ventriculostomy, fenestration of a cyst). The visual control reduces the hazard of injury to anatomical structures and allows for a better control of bleeding although there is a considerable blind-out in such situations. The advantages of stereotactic surgery include a smaller approach and precise planning of the trajectory. It is usually performed under local anaesthesia. Both methods provide a safe and efficient therapeutic option in periventricular lesions with low surgical-related morbidity.