What Have We Learned About Movement Disorders from Functional Neurosurgery?

Modern functional neurosurgery for movement disorders such as Parkinson's disease, tremor, and dystonia involves the placement of focal lesions or the application of deep brain stimulation (DBS) within circuits that modulate motor function. Precise targeting of these motor structures can be further refined by the use of electrophysiological approaches. In particular, microelectrode recordings enable the delineation of neuroanatomic structures. In the course of these operations, there is an opportunity not only to map basal ganglia structures but also to gain insights into how disturbances in neural activity produce movement disorders. In this review, we aim to highlight what the field has uncovered thus far about movement disorders through DBS. The work to date lays the foundation for future studies that will shed further light on dysfunctional circuits mediating diseases of the nervous system and how we might modulate these circuits therapeutically.

Outcomes of Focused Ultrasound Thalamotomy in Tremor Syndromes.

BACKGROUND: The current literature comparing outcomes after a unilateral magnetic resonance image-guided focused ultrasound (MRgFUS) thalamotomy between tremor syndromes is limited and remains a possible preoperative factor that could help predict the long-term outcomes. OBJECTIVE: The aim was to report on the outcomes between different tremor syndromes after a unilateral MRgFUS thalamotomy. METHODS: A total of 66 patients underwent a unilateral MRgFUS thalamotomy for tremor between November 2018 and May 2020 at St Vincent's Hospital Sydney. Each patient's tremor syndrome was classified prior to treatment. Clinical assessments, including the hand tremor score (HTS) and Quality of Life in Essential Tremor Questionnaire (QUEST), were performed at baseline and predefined intervals to 36 months. RESULTS: A total of 63 patients, comprising 30 essential tremor (ET), 24 dystonic tremor (DT), and 9 Parkinson's disease tremor (PDT) patients, returned for at least one follow-up. In the ET patients, at 24 months there was a 61% improvement in HTS and 50% improvement in QUEST compared to baseline. This is in comparison to PDT patients, where an initial benefit in HTS and QUEST was observed, which waned at each follow-up, remaining significant only up until 12 months. In the DT patients, similar results were observed to the ET patients: at 24 months there was a 61% improvement in HTS and 43% improvement in QUEST compared to baseline. CONCLUSION: These results support the use of unilateral MRgFUS thalamotomy for the treatment of DT, which appears to have a similar expected outcome to patients diagnosed with ET. Patients with PDT should be warned that there is a risk of treatment failure. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Focused Ultrasound for Treatment of Movement Disorders: A Review of Non-Food and Drug Administration Approved Indications.

INTRODUCTION: MRI-guided focused ultrasound (FUS) is an incisionless thermo-ablative procedure that may be used to treat medication-refractory movement disorders, with a growing number of potential anatomic targets and clinical applications. As of this article's publication, the only US Food and Drug Administration (FDA)-approved uses of FUS for movement disorders are thalamotomy for essential tremor (ET) and tremor-dominant Parkinson's Disease (PD), and pallidotomy for other cardinal symptoms of PD. We present a state-of-the-art review on all non-FDA approved indications of FUS for movement disorders, beyond the most well-described indications of ET and PD. Our objective was to summarize the safety and efficacy of FUS in this setting and provide a roadmap for future directions of FUS for movement disorders. METHODS: A state-of-the-art review was conducted on use of FUS for non-FDA approved movement disorders. All movement disorders excluding FDA-approved uses for ET and PD were included. RESULTS: A total of 25 studies on 172 patients were included. In patients with tremor plus dystonia syndromes (n = 6), ventralis intermediate nucleus of the thalamus (VIM)-FUS gave >50% tremor reduction, with no improvement in dystonia and worsened dystonia in 2/6 patients. Ventral-oralis complex (VO)-FUS gave >50% improvement for focal hand dystonia (n = 6) and 100% return to musical performance in musician's dystonia (n = 6). In patients with multiple sclerosis (MS) and tremor (n = 3), improvement in tremor was seen in 2 patients with a favorable skull density ratio; no MS disease change was noted after VIM-FUS. In patients with tremor and comorbid ataxia syndromes (n = 3), none were found to have worsened ataxia after VIM-FUS; all had clinically significant tremor improvement. Subthalamic nucleus (STN)-FUS for PD (n = 49) gave approximately 50% improvement in PD motor symptoms, with dystonia and mild dyskinesias as possible adverse effects. Cerebellothalamic tract (CTT-FUS) for ET (n = 42) gave 55-90% tremor improvement, with gait dysfunction as a rare persistent adverse effect. Pallidothalamic tract (PTT-FUS) for PD (n = 50) gave approximately 50% improvement in motor symptoms, with mild speech dysfunction as a possible adverse effect. CONCLUSION: VIM-FUS appeared safe and effective for heterogenous tremor etiologies, and VO-FUS appeared most effective for isolated segmental dystonia. STN-FUS was effective for PD symptom reduction; postoperative dystonia and mild on-medication dyskinesias required medical management. Tractography-based targeting with CTT-FUS for ET and PTT-FUS for PD demonstrated promising early results. Larger prospective trials with long-term follow-up are needed to the evaluate the safety and efficacy non-FDA approved indications for FUS.

Brainstem cavernous hemangioma with improvement of Holmes tremor on excision.

An 8-year-old boy presenting with left-angle paralysis, tremor in upper and lower extremities, and diplopia was diagnosed with hemorrhage from a mesencephalic cavernous hemangioma. He underwent hemangiomectomy through the occipital transtentorial approach 4 weeks post-hemorrhage, after which Holmes tremor (HT) markedly reduced. A year later, hemangioma has not recurred; he is now independent in his daily activities. Early intervention in the subacute stage allows for the complete removal of brainstem cavernomas (BSCs), with minimal risk of complications or sequelae. Proper timing and surgical approach for BSCs can prevent re-bleeding and improve HT after an initial hemorrhage, without any lasting negative consequences.

Impact of biologically effective dose on tremor decrease after stereotactic radiosurgical thalamotomy for essential tremor: a retrospective longitudinal analysis.

This letter to the editor critiques a recent study evaluating the role of biologically effective dose (BED) in stereotactic radiosurgical thalamotomy for essential tremor (ET). The study, conducted retrospectively on 78 ET patients, demonstrates a significant correlation between BED and tremor improvement post-SRS. Moreover, the study suggests adjusting the prescribed dose rather than changing cobalt-60 sources to maintain treatment efficacy while minimizing toxicity. This suggestion aligns with previous research indicating an annual decrease in BED due to cobalt-60 decay. The letter emphasizes the importance of considering BED and cobalt-60 decay in optimizing treatment outcomes for ET patients undergoing stereotactic radiosurgery. Further research is recommended to explore innovative techniques for dose modulation in response to cobalt-60 decay and validate findings in larger cohorts.

Objective clinical registration of tremor, bradykinesia, and rigidity during awake stereotactic neurosurgery: a scoping review.

Tremor, bradykinesia, and rigidity are incapacitating motor symptoms that can be suppressed with stereotactic neurosurgical treatment like deep brain stimulation (DBS) and ablative surgery (e.g., thalamotomy, pallidotomy). Traditionally, clinicians rely on clinical rating scales for intraoperative evaluation of these motor symptoms during awake stereotactic neurosurgery. However, these clinical scales have a relatively high inter-rater variability and rely on experienced raters. Therefore, objective registration (e.g., using movement sensors) is a reasonable extension for intraoperative assessment of tremor, bradykinesia, and rigidity. The main goal of this scoping review is to provide an overview of electronic motor measurements during awake stereotactic neurosurgery. The protocol was based on the PRISMA extension for scoping reviews. After a systematic database search (PubMed, Embase, and Web of Science), articles were screened for relevance. Hundred-and-three articles were subject to detailed screening. Key clinical and technical information was extracted. The inclusion criteria encompassed use of electronic motor measurements during stereotactic neurosurgery performed under local anesthesia. Twenty-three articles were included. These studies had various objectives, including correlating sensor-based outcome measures to clinical scores, identifying optimal DBS electrode positions, and translating clinical assessments to objective assessments. The studies were highly heterogeneous in device choice, sensor location, measurement protocol, design, outcome measures, and data analysis. This review shows that intraoperative quantification of motor symptoms is still limited by variable signal analysis techniques and lacking standardized measurement protocols. However, electronic motor measurements can complement visual evaluations and provide objective confirmation of correct placement of the DBS electrode and/or lesioning. On the long term, this might benefit patient outcomes and provide reliable outcome measures in scientific research.

Impact of biologically effective dose on tremor decrease after stereotactic radiosurgical thalamotomy for essential tremor: a retrospective longitudinal analysis.

Stereotactic radiosurgery (SRS) is one of the surgical alternatives for drug-resistant essential tremor (ET). Here, we aimed at evaluating whether biologically effective dose (BEDGy2.47) is relevant for tremor improvement after stereotactic radiosurgical thalamotomy in a population of patients treated with one (unplugged) isocenter and a uniform dose of 130 Gy. This is a retrospective longitudinal single center study. Seventy-eight consecutive patients were clinically analyzed. Mean age was 69.1 years (median 71, range 36-88). Mean follow-up period was 14 months (median 12, 3-36). Tremor improvement was assessed at 12 months after SRS using the ET rating assessment scale (TETRAS, continuous outcome) and binary (binary outcome). BED was defined for an alpha/beta of 2.47, based upon previous studies considering such a value for the normal brain. Mean BED was 4573.1 Gy2.47 (median 4612, 4022.1-4944.7). Mean beam-on time was 64.7 min (median 61.4; 46.8-98.5). There was a statically significant correlation between delta (follow-up minus baseline) in TETRAS (total) with BED (p = 0.04; beta coefficient - 0.029) and beam-on time (p = 0.03; beta coefficient 0.57) but also between TETRAS (ADL) with BED (p = 0.02; beta coefficient 0.038) and beam-on time (p = 0.01; beta coefficient 0.71). Fractional polynomial multivariate regression suggested that a BED > 4600 Gy2.47 and a beam-on time > 70 min did not further increase clinical efficacy (binary outcome). Adverse radiation events (ARE) were defined as larger MR signature on 1-year follow-up MRI and were present in 7 out of 78 (8.9%) cases, receiving a mean BED of 4650 Gy2.47 (median 4650, range 4466-4894). They were clinically relevant with transient hemiparesis in 5 (6.4%) patients, all with BED values higher than 4500 Gy2.47. Tremor improvement was correlated with BED Gy2.47 after SRS for drug-resistant ET. An optimal BED value for tremor improvement was 4300-4500 Gy2.47. ARE appeared for a BED of more than 4500 Gy2.47. Such finding should be validated in larger cohorts.

An evaluation of physical and augmented patient-specific intracranial aneurysm simulators on microsurgical clipping performance and skills: a randomized controlled study.

OBJECTIVE: In the era of flow diversion, there is an increasing demand to train neurosurgeons outside the operating room in safely performing clipping of unruptured intracranial aneurysms. This study introduces a clip training simulation platform for residents and aspiring cerebrovascular neurosurgeons, with the aim to visualize peri-aneurysm anatomy and train virtual clipping applications on the matching physical aneurysm cases. METHODS: Novel, cost-efficient techniques allow the fabrication of realistic aneurysm phantom models and the additional integration of holographic augmented reality (AR) simulations. Specialists preselected suitable and unsuitable clips for each of the 5 patient-specific models, which were then used in a standardized protocol involving 9 resident participants. Participants underwent four sessions of clip applications on the models, receiving no interim training (control), a video review session (video), or a video review session and holographic clip simulation training (video + AR) between sessions 2 and 3. The study evaluated objective microsurgical skills, which included clip selection, number of clip applications, active simulation time, wrist tremor analysis during simulations, and occlusion efficacy. Aneurysm occlusions of the reference sessions were assessed by indocyanine green videoangiography, as well as conventional and photon-counting CT scans. RESULTS: A total of 180 clipping procedures were performed without technical complications. The measurements of the active simulation times showed a 39% improvement for all participants. A median of 2 clip application attempts per case was required during the final session, with significant improvement observed in experienced residents (postgraduate year 5 or 6). Wrist tremor improved by 29% overall. The objectively assessed aneurysm occlusion rate (Raymond-Roy class 1) improved from 76% to 80% overall, even reaching 93% in the extensively trained cohort (video + AR) (p = 0.046). CONCLUSIONS: The authors introduce a newly developed simulator training platform combining physical and holographic aneurysm clipping simulators. The development of exchangeable, aneurysm-comprising housings allows objective radio-anatomical evaluation through conventional and photon-counting CT scans. Measurable performance metrics serve to objectively document improvements in microsurgical skills and surgical confidence. Moreover, the different training levels enable a training program tailored to the cerebrovascular trainees' levels of experience and needs.

Gamma knife thalamotomy in treating refractory tremor: initial clinical experience in Croatia.

Tremor refractory to pharmacological therapy significantly reduces the patient´s quality of life, often leading to early retirement and social isolation. Gamma knife (GK) stereotactic radiosurgery of the unilateral thalamic ventral intermediate nucleus is an advanced, minimally invasive surgical procedure for symptomatic tremor suppression. Due to the restricted availability of this type of treatment, literature data on its efficacy and safety are lacking. We present two patients with severe, disabling tremor (one with parkinsonian and one with essential tremor) successfully treated with GK thalamotomy, performed in Croatia for the first time. GK thalamotomy should be considered in patients with refractory tremors and contraindications for deep brain stimulation.

Unilateral gamma knife thalamotomy for tremor safety and efficacy in multimodal assessment: a prospective case-control study with two-year follow-up.

INTRODUCTION: Unilateral gamma knife thalamotomy (GKT) is a treatment option for pharmacoresistant tremor of various aetiologies. There have been to date no randomised controlled trials performed to assess its safety and efficacy. Our aim was to summarise a two-year multimodal observation of patients with tremor caused by Parkinson's Disease (PD) or essential tremor (ET). MATERIAL AND METHODS: 23 patients with PD (n = 12) or ET (n = 11) were included. They underwent assessments before, V0 (n = 23), and 12 months, V12 (n = 23), and 24 months, V24 (n = 15), after unilateral GKT. Patients were assessed with psychological tests and acoustic voice analysis. Tremor assessment was performed with a digitising table using the Fahn-Tolosa-Marin rating scale (FTMRS). The Unified Parkinson's Disease rating scale part III (UPDRS-III) was also used in the PD group. Gait and balance was assessed using clinical tests, stabilometric platform, and treadmill. RESULTS: No side effects were observed in a two-year follow-up. There was no notable deterioration observed in the patients' psychological evaluation, speech, or assessment of gait and balance. The scores were significantly lower (p = 0.01) in parts A and B of FTMRS one year after GKT. In post hoc analysis, the scores did not differ significantly between V0 and V24. In FTMRS part C (activities of daily living), no significant change was observed. There was no significant difference in total UPDRS part III score or in score of UPDRS part III domains 3 and 4 ('tremor at rest' and 'action and postural tremor of hands') between measurements. CONCLUSIONS: UGKT may be a safe treatment modality if performed in an experienced centre. Tremor reduction may diminish over time, and UGKT did not lead to cognitive, gait or speech deterioration in a long-term observation.

Limb Preference Changes after Focused-Ultrasound Thalamotomy for Tremor.

BACKGROUND: Magnetic resonance-guided focused-ultrasound (MRgFUS) thalamotomy is an effective treatment for essential and other tremors. It targets the ventrointermedius (Vim) nucleus, which is the thalamic relay in a proprioceptive pathway, and contains kinesthetic cells. Although MRgFUS thalamotomy reduces some risks associated with more invasive surgeries, it still has side effects, such as balance and gait disturbances; these may be caused by the lesion impacting proprioception. OBJECTIVES: Our aim was to quantitatively measure the effects of MRgFUS on proprioception and limb use in essential tremor patients. We hypothesized that this thalamotomy alters proprioception, because the sensorimotor Vim thalamus is lesioned. METHODS: Proprioception was measured using the Kinarm exoskeleton robot in 18 patients. Data were collected pre-operatively, and then 1 day, 3 months, and 1 year after surgery. Patients completed four tasks, assessing motor coordination and postural control, goal-directed movement and bimanual planning, position sense, and kinesthesia. RESULTS: Immediately after surgery there were changes in posture speed (indicating tremor improvement), and in bimanual hand use, with the untreated limb being preferred. However, these measures returned to pre-operative baseline over time. There were no changes in parameters related to proprioception. None of these measures correlated with lesion size or lesion-overlap with the dentato-rubro-thalamic tract. CONCLUSIONS: This is the first quantitative assessment of proprioception and limb preference following MRgFUS thalamotomy. Our results suggest that focused-ultrasound lesioning of the Vim thalamus does not degrade proprioception but alters limb preference. This change may indicate a required "relearning" in the treated limb, because the effect is transient. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Focused Ultrasound Thalamotomy for Tremor in Parkinson's Disease: Outcomes in a Large, Prospective Cohort.

BACKGROUND: Magnetic resonance guided focused ultrasound (MRgFUS) is United States Food and Drug Administration approved for the treatment of tremor-dominant Parkinson's disease (TdPD), but only limited studies have been described in practice. OBJECTIVES: To report the largest prospective experience of unilateral MRgFUS thalamotomy for the treatment of medically refractory TdPD. METHODS: Clinical outcomes of 48 patients with medically refractory TdPD who underwent MRgFUS thalamotomy were evaluated. Tremor outcomes were assessed using the Fahn-Tolosa-Marin scale and adverse effects were categorized using a structured questionnaire and clinical exam at 1 month (n = 44), 3 months (n = 34), 1 year (n = 22), 2 years (n = 5), and 3 years (n = 2). Patients underwent magnetic resonance imaging <24 hours post-procedure. RESULTS: Significant tremor control persisted at all follow-ups (P < 0.001). All side effects were mild. At 3 months, these included gait imbalance (38.24%), sensory deficits (26.47%), motor weakness (17.65%), dysgeusia (5.88%), and dysarthria (5.88%), with some persisting at 1 year. CONCLUSIONS: MRgFUS thalamotomy is an effective treatment for sustained tremor control in patients with TdPD. © 2023 International Parkinson and Movement Disorder Society.

Deep brain stimulation of the dentato-rubro-thalamic tract in a case of Holmes tremor: a constrained spherical deconvolution (CSD)-guided procedure.

Deep brain stimulation (DBS) is an established treatment for movement disorders, including Holmes tremor (HT). HT is a rest and action tremor that occurs as a late symptom of brainstem lesions such as stroke. Unfortunately, it is frequently refractory to medical treatment, hence DBS surgery may be a good option. Due to variable results, the ideal target for DBS in HT still remains to be established, ranging from the thalamus to the globus pallidus internus, to the subthalamic nucleus. Pre-operative imaging also is very challenging, as the complexity of brain fiber architecture may prevent the correct positioning of the directional lead. Herein, we describe the case of a patient affected by a rubral tremor secondary to a brain hemorrhage, who had advanced pre-operative neuroimaging with constrained spherical deconvolution (CSD)-based tractography obtained from diffusion-weighted imaging (DWI) to identify the dentato-rubro-thalamic tract, involved in the pathophysiology of HT. The patient was then addressed to an awake DBS surgery, and with the help of intraoperative microelectrode recordings, a tailored DRTT-targeted procedure was performed. The stimulation determined an almost complete tremor suppression, with no significant side effects at a follow-up of 6 months, paving the way towards new effective techniques for the planning, i.e., CSD-based tractography and the treatment of refractory tremors.

Successful MRI-Guided Focused Ultrasound Thalamotomy after Ipsilateral Gamma Knife Radiosurgery for Essential Tremor: A Case Report with Video.

We report the case of a 67-year-old left-handed female patient with disabling medically refractory essential tremor who underwent successful right-sided magnetic resonance-guided focused ultrasound (MRgFUS) of the ventral intermediate nucleus after ipsilateral gamma knife radiosurgery (GKRS) thalamotomy performed 3 years earlier. The GKRS had a partial effect on her postural tremor without side effects, but there was no reduction of her kinetic tremor or improvement in her quality of life (QoL). The patient subsequently underwent a MRgFUS thalamotomy, which induced an immediate and marked reduction in both the postural and kinetic tremor components, with minor complications (left upper lip hypesthesia, dysmetria in her left hand, and slight gait ataxia). The MRgFUS-induced lesion was centered more medially than the GKRS-induced lesion and extended more posteriorly and inferiorly. The MRgFUS-induced lesion interrupted remaining fibers of the dentatorubrothalamic tract (DRTT). The functional improvement 1-year post-MRgFUS was significant due to a marked reduction of the patient's kinetic tremor. The QoL score (Quality of Life in Essential Tremor) improved by 88% and her Clinical Rating Scale for Tremor left hand score by 62%. The side effects persisted but were minor, with no impact on her QoL. The explanation for the superior efficacy of MRgFUS compared to GKRS in our patient could be due to either a poor response to the GKRS or to a better localization of the MRgFUS lesion with a more extensive interruption of DRTT fibers. In conclusion, MRgFUS can be a valuable therapeutic option after unsatisfactory GKRS, especially because MRgFUS has immediate clinical effectiveness, allowing intra-procedural test lesions and possible readjustment of the target if necessary.

Neurosurgical management of non-spastic movement disorders.

BACKGROUND: Non-spastic movement disorders in children are common, although true epidemiologic data is difficult to ascertain. Children are more likely than adults to have hyperkinetic movement disorders defined as tics, dystonia, chorea/athetosis, or tremor. These conditions manifest from acquired or heredodegenerative etiologies and often severely limit function despite medical and surgical management paradigms. Neurosurgical management for these conditions is highlighted. METHODS: We performed a focused review of the literature by searching PubMed on 16 May 2023 using key terms related to our review. No temporal filter was applied, but only English articles were considered. We searched for the terms (("Pallidotomy"[Mesh]) OR "Rhizotomy"[Mesh]) OR "Deep Brain Stimulation"[Mesh], dystonia, children, adolescent, pediatric, globus pallidus, in combination. All articles were reviewed for inclusion in the final reference list. RESULTS: Our search terms returned 37 articles from 2004 to 2023. Articles covering deep brain stimulation were the most common (n = 34) followed by pallidotomy (n = 3); there were no articles on rhizotomy. DISCUSSION: Non-spastic movement disorders are common in children and difficult to treat. Most of these patients are referred to neurosurgery for the management of dystonia, with modern neurosurgical management including pallidotomy, rhizotomy, and deep brain stimulation. Historically, pallidotomy has been effective and may still be preferred in subpopulations presenting either in status dystonicus or with high risk for hardware complications. Superiority of DBS over pallidotomy for secondary dystonia has not been determined. Rhizotomy is an underutilized surgical tool and more study characterizing efficacy and risk profile is indicated.

MRgFUS thalamotomy for the treatment of tremor: evaluation of learning curve and operator's experience impact on the procedural and clinical outcome.

BACKGROUND: MRgFUS Vim ablation is increasingly used for the treatment of tremor in ET e PD patients but there is little published research on the importance of operator experience in this procedure. This study aims to evaluate the learning curve and the influence of the operator experience on the procedural and clinical outcomes. METHODS: We retrospectively evaluated 90 patients (38 ET, 52 PD) submitted to MRgFUS unilateral thalamotomy in the period between February 2018 and July 2020. Clinical endpoints, procedural times, and technical parameters were recorded in all procedures. Based on the time of treatment, patients were divided into three groups of 30 units each, comparing all variables between each time period group. RESULTS: In Group A, the average patient preparation time was 120.6 min, the treatment time was 105.2 min, the number of was sonications 14.1, and the mean target shifts 3.1. In Group B, the mean preparation time was 105.5 min, the treatment time was 89.5 min, the number of sonications was 13.2, and the target shifts 3.0. Group C showed inferior values of preparation time (101.9 min), treatment time (71.7 min), numbers of sonications (10.6), and shifts (1.7). Thalamotomy-related complications occurred in 9 patients of Group A, 2 of Group B, and 5 of Group C. Tremor relapse occurred in 7 patients of Group A, 3 of Group B, and 2 of Group C. The days of hospitalization were comparable in the three groups. CONCLUSIONS: The operators experience is associated with the improvement of clinical and procedural outcome in MRgFUS thalatomy for the treatment of ET and PD tremor.

Stereotactic robot-assisted MRI-guided laser interstitial thermal therapy thalamotomy for medically intractable Parkinson's disease tremor: technical note and preliminary effects on 2 cases.

BACKGROUND: Medically intractable Parkinson's disease (PD) tremor is a common difficult clinical situation with major impact on patient's quality of life (QOL). Deep brain stimulation (DBS) is an effective therapy but is not an option for many patients. Less invasive lesional brain surgery procedures, such as thalamotomy, have proven to be effective in these indications. Here, we describe the technical nuances and advantages of stereotactic robot-assisted MRI-guided laser interstitial thermal therapy (MRIg-LITT) thalamotomy for medically intractable PD tremor. METHOD: We describe 2 patients with medically intractable PD tremor treated with stereotactic robot-assisted MRIg-LITT thalamotomy performed under general anesthesia with intraoperative electrophysiological testing. Pre and postoperative tremor scores were assessed using the Fahn-Tolosa-Marin tremor rating scale (TRS). RESULTS: At 3-month follow-up, both patients demonstrated significant improvement in tremor symptoms subjectively and according to the TRS (75% for both). Patients also had substantial improvements in their QOL (32.54% and 38%) according to the 39-item PD questionnaire. Both patients underwent uncomplicated MRIg-LITT thalamotomy. CONCLUSIONS: In patients with medically intractable PD tremor who are unsuitable candidates for DBS, thalamotomy utilizing a stereotactic robot, intraoperative electrophysiological testing, and laser ablation with real-time MRI guidance may be a viable treatment option. However, further studies with larger sample sizes and longer follow-up periods are necessary to confirm these preliminary results.

Cavitation with low-energy sonication during focused ultrasound thalamotomy for a patient with tremor-dominant Parkinson's disease: a potential risk.

We report a patient with tremor-dominant Parkinson's disease who had a mild cavitation bioeffect during magnetic resonance-guided focused ultrasound thalamotomy. During the aligning phase with low-energy sonication, cavitation caused mild dysarthria and paresthesia, prompting treatment cessation. At the same time, tremor and rigidity improved. MRI revealed extensive high-intensity lesions in the thalamus 1 day after the procedure followed by steroid infusion, which resulted in resolution of adverse events. Tremor and rigidity improved 1.5 years after the procedure. Although cavitation can relieve tremors and rigidity, it should be carefully monitored due to potential permanent adverse events by unpredictable and unknown behaviors.

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.

Magnetic Resonance-Guided Focused Ultrasound Thalamotomy May Spare Dopaminergic Therapy in Early-Stage Tremor-Dominant Parkinson's Disease: A Pilot Study.

BACKGROUND: Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy is a safe and effective procedure for drug-resistant tremor in Parkinson's disease (PD). OBJECTIVE: The aim of this study was to demonstrate that MRgFUS ventralis intermedius thalamotomy in early-stage tremor-dominant PD may prevent an increase in dopaminergic medication 6 months after treatment compared with matched PD control subjects on standard medical therapy. METHODS: We prospectively enrolled patients with early-stage PD who underwent MRgFUS ventralis intermedius thalamotomy (PD-FUS) and patients treated with oral dopaminergic therapy (PD-ODT) with a 1:2 ratio. We collected demographic and clinical data at baseline and 6 and 12 months after thalamotomy. RESULTS: We included 10 patients in the PD-FUS group and 20 patients in the PD-ODT group. We found a significant increase in total levodopa equivalent daily dose and levodopa plus monoamine oxidase B inhibitors dose in the PD-ODT group 6 months after thalamotomy. CONCLUSIONS: In early-stage tremor-dominant PD, MRgFUS thalamotomy may be useful to reduce tremor and avoid the need to increase dopaminergic medications. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.