Essential tremor (ET) is the most common movement disorder. Deep brain stimulation (DBS) targeting the ventral intermediate nucleus (VIM) is known to improve symptoms in patients with medication-resistant ET. However, the clinical effectiveness of VIM-DBS may vary, and other targets have been proposed. The authors aimed to investigate whether the same anatomical structure is responsible for tremor control both immediately after VIM-DBS and at later follow-up evaluations.
Of 68 electrodes from 41 patients with ET, the authors mapped the distances of the active contact from the VIM, the dentatorubrothalamic tract (DRTT), and the caudal zona incerta (cZI) and compared them using Friedman\'s ANOVA and the Wilcoxon signed-rank follow-up test. The same distances were also compared between the initially planned target and the final implantation site after intraoperative macrostimulation. Finally, the comparison among the three structures was repeated for 16 electrodes whose active contact was changed after a mean 37.5 months follow-up to improve tremor control.
After lead implantation, the VIM was statistically significantly closer to the active contact than both the DRTT (p = 0.008) and cZI (p < 0.001). This result did not change if the target was moved based on intraoperative macrostimulation. At the last follow-up, the active contact distance from the VIM was always significantly less than that of the cZI (p < 0.001), but the distance from the DRTT was reduced and even less than the distance from the VIM.
In patients receiving VIM-DBS, the VIM itself is the structure driving the anti-tremor effect and remains more effective than the cZI, even years after implantation. Nevertheless, the role of the DRTT may become more important over time and may help sustain the clinical efficacy when the habituation from the VIM stimulation ensues.

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a peripheral neuropathy caused by immune-mediated demyelination, causing tremors in 3.9%-58% of affected patients. This neuropathic tremor may persist after treatment and is known to be refractory to conventional medication. We present two cases of neuropathic tremor due to CIDP in which deep brain stimulation (DBS) over a long-term period led to marked improvement. Case 1: A 66-year-old woman presented with severe 2-3-Hz resting, postural, and kinetic tremors of both hands. The tremor was refractory to medication but improved well after bilateral VIM-DBS. However, 2 months after the procedure, the tremor worsened and was accompanied by sensory disturbance in the extremities. A diagnosis of CIDP was made, and treatment with corticosteroids and intravenous immunoglobulin achieved remission 6 months later. Although there was residual tremor after CIDP remission, it has been well controlled by DBS for the last 10 years. Case 2: A 56-year-old man presented with a 6-year history of CIDP after developing sensory dullness and tremors in the extremities. The CIDP had gone into remission 1 year previously and the sensory deficits had improved, but the tremors had gradually worsened: severe 8-12-Hz postural, kinetic, and resting tremors were present in both upper extremities. Right VIM-DBS was performed and the tremors on the left side showed marked improvement. Over the next 8 years, the tremors were well controlled and there were no relapses of CIDP. DBS may achieve long-term improvement of neuropathic tremor caused by CIDP if the CIDP is in remission.

BACKGROUND: The ventral intermediate nucleus (Vim) of the thalamus is a surgical target for treating various types of tremor. Because it is difficult to visualize the Vim using standard magnetic resonance imaging, the structure is usually targeted based on the anterior and posterior commissures. This standard targeting method is practical in most patients but not in those with thalamic asymmetry. The authors examined the usefulness of quantitative susceptibility mapping (QSM) and transformed Vim atlas images to estimate the Vim localization in a patient with tremor and significant thalamic hypertrophy.
METHODS: A 51-year-old right-handed female had experienced a predominant left-hand action tremor for 6 years. Magnetic resonance imaging showed significant hypertrophy of the right thalamus and caudal shift of the thalamic ventral border. The authors referred to the QSM images to localize the decreased susceptibility area within the lateral ventral thalamic nuclei to target the Vim. In addition, the nonlinearly transformed Vim atlas images complemented the imaging-based targeting. The radiofrequency thalamotomy at the modified Vim target relieved the tremor completely.
CONCLUSIONS: A combination of QSM and nonlinear transformation of the thalamic atlas can be helpful in the targeting method of the Vim for tremor patients with thalamic asymmetry.

The primary aim of this study is to report long-term outcomes associated with deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) performed at our institution. We further aimed to elicit the factors associated with loss of efficacy and to discuss the need for exploring and establishing reliable rescue targets.
To study long-term outcomes, we performed a retrospective chart review and extracted tremor scores of 43 patients who underwent VIM DBS lead implantation for essential tremor at our center. We further evaluated factors that could influence outcomes over time, including demographics, body mass index, duration of follow-up, degree of parenchymal atrophy indexed by the global cortical atrophy scale, and third ventricular width.
In this cohort, tremor scores on the latest follow-up (median 52.7 months) were noted to be worse than initial postoperative scores in 56% of DBS leads. Furthermore, 14% of leads were associated with clinically significant loss of benefit. Factors including the length of time since the lead implantation, age at the time of surgery, sex, body mass index, preoperative atrophy, and third ventricular width were not predictive of long-term outcomes.
Our study identified a substantial subgroup of VIM-DBS patient who experienced a gradual decline in treatment efficacy over time. We propose that this phenomenon can be attributed primarily to habituation and disease progression. Furthermore, we discuss the need to establish reliable and effective rescue targets for this subpopulation of patients, with ventral-oralis complex and dentate nucleus emerging as potential candidates.

BACKGROUND: Magnetic resonance-guided focused ultrasound (MRgFUS) for treatment of essential tremor (ET) traditionally targets the ventral intermediate (Vim) nucleus. Recent strategies include a secondary lesion to the posterior subthalamic area (PSA).
OBJECTIVE: The aim was to compare lesion characteristics, tremor improvement, and adverse events (AE) between patients in whom satisfactory tremor suppression was achieved with lesioning of the Vim alone and patients who required additional lesioning of the PSA.
METHODS: Retrospective analysis of data collected from ET patients treated with MRgFUS at St Vincent\'s Hospital Sydney was performed. Clinical Rating Scale for Tremor (CRST), hand tremor score (HTS), and Quality of Life in Essential Tremor Questionnaire (QUEST) were collected pre- and posttreatment in addition to the prevalence of AEs. The lesion coordinates and overlap with the dentatorubrothalamic tract (DRTT) were evaluated using magnetic resonance imaging.
RESULTS: Twenty-one patients were treated in Vim only, and 14 were treated with dual Vim-PSA lesions. Clinical data were available for 29 of the 35 patients (19 single target and 10 dual target). At follow-up (mean: 18.80 months) HTS, CRST, and QUEST in single-target patients improved by 57.97% (P < 0.001), 36.71% (P < 0.001), and 58.26% (P < 0.001), whereas dual-target patients improved by 68.34% (P < 0.001), 35.37% (P < 0.003), and 46.97% (P < 0.005), respectively. The Vim lesion of dual-target patients was further anterior relative to the posterior commissure (PC) (7.84 mm), compared with single-target patients (6.92 mm), with less DRTT involvement (14.85% vs. 23.21%). Dual-target patients exhibited a greater proportion of patients with acute motor AEs (100% vs. 58%); however, motor AE prevalence was similar in both groups at long-term follow-up (33% vs. 38%).
CONCLUSIONS: Posterior placement of lesions targeting the Vim may confer greater tremor suppression. The addition of a PSA lesion, in patients with inadequate tremor control despite Vim lesioning, had a trend toward better long-term tremor suppression; however, this approach was associated with greater prevalence of gait disturbance in the short term.

BACKGROUND: The ventral intermediate nucleus of the thalamus (VIM) is an effective target for deep brain stimulation in tremor patients. Despite its therapeutic importance, its oscillatory coupling to cortical areas has rarely been investigated in humans.
OBJECTIVE: The objective of this study was to identify the cortical areas coupled to the VIM in patients with essential tremor.
METHODS: We combined resting-state magnetoencephalography with local field potential recordings from the VIM of 19 essential tremor patients. Whole-brain maps of VIM-cortex coherence in several frequency bands were constructed using beamforming and compared with corresponding maps of subthalamic nucleus (STN) coherence based on data from 19 patients with Parkinson\'s disease. In addition, we computed spectral Granger causality.
RESULTS: The topographies of VIM-cortex and STN-cortex coherence were very similar overall but differed quantitatively. Both nuclei were coupled to the ipsilateral sensorimotor cortex in the high-beta band; to the sensorimotor cortex, brainstem, and cerebellum in the low-beta band; and to the temporal cortex, brainstem, and cerebellum in the alpha band. High-beta coherence to sensorimotor cortex was stronger for the STN (P = 0.014), whereas low-beta coherence to the brainstem was stronger for the VIM (P = 0.017). Although the STN was driven by cortical activity in the high-beta band, the VIM led the sensorimotor cortex in the alpha band.
CONCLUSIONS: Thalamo-cortical coupling is spatially and spectrally organized. The overall similar topographies of VIM-cortex and STN-cortex coherence suggest that functional connections are not necessarily unique to one subcortical structure but might reflect larger frequency-specific networks involving VIM and STN to a different degree. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

UNASSIGNED: Deep brain stimulation (DBS) surgery targeting the ventral intermediate thalamic nucleus (Vim) has proven efficacy in the treatment of tremor.
UNASSIGNED: The primary aim is to investigate whether there is a statistically significant difference in patient outcomes when CT-guided targeting of the Vim is compared with MRI-guided targeting.
UNASSIGNED: This is a retrospective study concerning patients undergoing Vim-targeted DBS at the Department of Neurosurgery, Royal Victoria Infirmary in Newcastle (9th August 2012 to 4th January 2019). Fahn-Tolosa-Marin Tremor Scale (FTM TS) and EQ-5D scores were collected from patient notes. Statistical analysis was performed using IBM® SPSS® Statistics Version 24. Independent samples t-tests were used to compare means.
UNASSIGNED: Independent samples t-test did not reveal a statistically significant difference between CT (n = 10; FTM TS mean = 65.40, SD = 11.40; EQ-5D mean = 39.50, SD = 17.87) and MR (n = 7; FTM TS mean = 60.57, SD = 7.50; EQ-5D mean = 32.14, SD = 9.94) groups in pre-surgery FTM TS (t(15) = 0.977, p = 0.344) and EQ-5D (t(15) = 0.982, p = 0.342) scores. No statistically significant difference between the CT (FTM TS mean = 24.12, SD = 20.47; EQ-5D mean = 75.56, SD = 15.63) and MR (FTM TS mean = 22.86, SD = 6.72; EQ-5D mean = 70.43, SD = 15.48) groups was revealed at 1 year assessment of FTM TS (t(14) = 0.155, p = 0.879) and EQ-5D (t(14) = 0.654, p = 0.524). The median difference between pre- and post-surgery FTM TS and EQ-5D scores in the CT group at 1 year was 43.00 and 35.00, respectively. The MR patient group median difference in pre- and post-surgery at 1 year was 35.00 and 35.00 respectively.
UNASSIGNED: No statistically significant difference between CT and MR image-guided targeting patient groups was detected.

OBJECTIVE: Deep brain stimulation (DBS) is a common procedure in neurosurgery used for the treatment of Parkinson\'s disease (PD) and essential tremor (ET) among other disorders. Lower urinary tract dysfunction is a common complication in PD, and this study aimed to evaluate the risk factors of postoperative urinary retention (POUR) after DBS surgery in patients with PD compared with patients with ET. Understanding the risk factors associated with this complication may help in the development of strategies to minimize its occurrence and improve patient outcomes.
METHODS: The study was a retrospective analysis of patients who underwent DBS surgery for PD and ET at the University of Florida between 2010 and 2021. The surgical technique used has been described in previous articles and included a two-stage procedure, with stage 1 involving burr hole placement, microelectrode recording, and electrode implantation and stage 2 involving the placement of an implantable pulse generator (IPG). Data were collected on patient characteristics and surgical details and analyzed using univariate and mixed-linear models. Post hoc propensity score matching was used to confirm the association between subthalamic nucleus (STN)-DBS and POUR.
RESULTS: The study included 350 patients (153 with PD and 197 with ET) who underwent 1086 DBS surgeries (lead implantations, IPG placement, and IPG replacements). The POUR rates were 16.6% (79/477), 5.2% (19/363), and 0.4% (1/246) for stage 1, stage 2, and IPG replacement procedures, respectively. Optimal mixed-effects logistic modeling revealed history of urinary retention (OR 9.3, p = 0.004), male sex (OR 2.7, p = 0.011), having an electrode placed or connected for the first time (OR 2.2, p = 0.014), anesthesia time (OR 1.5 for each 30-minute increase, p < 0.0001), preoperative opioid use (OR 1.4 for each additional 10 morphine milligram equivalents, p = 0.032), and Charlson Comorbidity Index (OR 1.4 per comorbidity, p = 0.017) to be significant risk factors for POUR. Having an electrode in the STN was found to be protective of POUR (propensity score-matched analysis: OR 0.2, p = 0.010).
CONCLUSIONS: Most risk factors found to increase the risk of POUR in DBS are not modifiable but are still important to consider in preoperative planning. Opioid use reduction and shorter anesthesia time may be modifiable risk factors to weigh against their alternative. Targeting the STN during DBS may result in decreased rates of POUR. This highlights the potential for STN-targeted DBS in reducing POUR risk in PD and ET patients.

UNASSIGNED: Tremor-dominant Parkinson\'s disease (TD-PD) can be further separated into levodopa-responsive and levodopa-resistant types, the latter being considered to have a different pathogenesis. Previous studies indicated that deep brain stimulation (DBS) of the subthalamic nucleus (STN) or the globus pallidus internus (GPi) individually was not sufficient for tremor control, especially for the levodopa-resistant TD-PD (LRTD-PD). The thalamic ventral intermediate nucleus (VIM) has been regarded as a potent DBS target for different kinds of tremors. Therefore, we focused on the LRTD-PD subgroup and performed one-pass combined DBSs of STN and VIM to treat refractory tremors, aiming to investigate the safety and effectiveness of this one-trajectory dual-target DBS scheme.
UNASSIGNED: We retrospectively collected five LRTD-PD patients who underwent a one-pass combined DBS of STN and VIM via a trans-frontal approach. The targeting of VIM was achieved by probabilistic tractography. Changes in severity of symptoms (measured by the Unified Parkinson Disease Rating Scale part III, UPDRS-III), levodopa equivalent daily doses (LEDD), and disease-specific quality of life (measured by the 39-item Parkinson\'s Disease Questionnaire, PDQ-39) were evaluated.
UNASSIGNED: Three-dimensional reconstruction of electrodes illustrated that all leads were successfully implanted into predefined positions. The mean improvement rates (%) were 53 ± 6.2 (UPDRS-III), 82.6 ± 11.4 (tremor-related items of UPDRS), and 52.1 ± 11.4 (PDQ-39), respectively, with a mean follow-up of 11.4 months.
UNASSIGNED: One-pass combined DBS of STN and VIM via the trans-frontal approach is an effective and safe strategy to alleviate symptoms for LRTD-PD patients.

UNASSIGNED: The thalamic ventral intermediate nucleus (Vim) and globus pallidus internus are far apart and cannot be captured using a single electrode.
UNASSIGNED: We describe our experience with a patient with dystonic tremors of the head and upper and lower extremities who showed symptomatic improvement after radiofrequency (RF) ablation using a parietal lobe approach with a single trajectory to capture the pallidothalamic tract and Vim. A 46-year-old man developed head tremors at 41 and a right-sided neck tilt three years later. Five years after the onset of the head tremors, tightness of the larynx during speech and tremors in both the upper and lower limbs also appeared. The Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) score was 24, and the Fahn-Tolosa-Marin Tremor Rating Scale (FTM) score was 48. We captured the pallidothalamic tract and Vim along a single trajectory by locating the entry point in the inferior parietal lobule. One week after treatment, the TWSTRS and FTM scale scores were 9 (62.5%) and 30 (37.5%), respectively. No adverse events were observed.
UNASSIGNED: This case suggests that in dystonic tremors involving abnormalities of the basal ganglia-thalamo-cortical and cerebello-thalamo-cortical circuits, a single electrode can be used to approach both circuits through the parietal lobe approach.