Which one is the superior target? A comparison and pooled analysis between posterior subthalamic area and ventral intermediate nucleus deep brain stimulation for essential tremor

Magnetic Resonance-Guided Focused Ultrasound for Treatment of Essential Tremor: Ventral Intermediate Nucleus Ablation Alone or Additional Posterior Subthalamic Area Lesioning?

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%).

CONCLUSION

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.

Technical Issues of Vim–PSA Double-Target DBS for Essential Tremor

Background: Deep brain stimulation (DBS) is an effective surgical treatment for essential tremor (ET), with the ventral intermediate nucleus (Vim) and posterior subthalamic area (PSA) as the most common targets. The stimulation efficacy of ET with Vim–PSA double-target DBS has been reported. Herein, we aim to propose surgical techniques for Vim–PSA double-target DBS surgery. Methods: This study enrolled six patients with ET who underwent Vim–PSA double-target electrode implantation from October 2019 to May 2022. The targets were located and adjusted using coordinates and multimodality MRI images. A burr hole was accurately drilled in line with the electrode trajectory under the guidance of a stereotactic frame. Novel approaches were adopted during the electrode implantation process for pneumocephalus reduction, including “arachnoid piamater welding” and “water sealing”. Electrophysiological recording was used to identify the implantation sites of the electrodes. A 3D reconstruction model of electrodes and nuclei was established to facilitate programming. Results: The combination of coordinates and multimodality MRI images for target location and adjustment enabled the alignment of Vim and PSA. Postoperative CT scanning showed that the electrode was precisely implanted. Stereotactic guidance facilitated accurate burr hole drilling. “Arachnoid piamater welding” and “water sealing” were efficient in reducing pneumocephalus. Intraoperative electrophysiological verified the efficacy of Vim–PSA double-target DBS surgery. Conclusions: The methods for target location and adjustment, accurate drilling of the burr hole, reduction in pneumocephalus, and intraoperative electrophysiological verification are key issues in DBS surgery targeting both the Vim and PSA. This study may provide technical support for Vim–PSA DBS, especially for surgeons with less experience in functional neurosurgery.

Deep brain stimulation of the posterior subthalamic area as an alternative strategy for management of Holmes tremor: A case report and review of the literature

Background:

Holmes tremor is often refractory to medical treatment and deep brain stimulation of the ventralis intermedius nucleus of the thalamus (VIM-DBS) is the intervention of choice in controlling the tremor. Herein, we present a beneficial alternative strategy for the management of such situations, considering the posterior subthalamic area (PSA) as the target of stimulation.

Case Description:

We report a 57-year-old male with the right-sided tremor following a traumatic brain injury 20 years ago. He had been diagnosed with Holmes tremor that was not responsive to nonsurgical therapeutic options. When refractoriness confirmed, he became a candidate for VIM-DBS. During the operation, by performing macrostimulation with a maximum of 2 mA of amplitude, the tremor had no response to the stimulation of different tracts, and severe right hemi-body paresthesia occurred; therefore, we modified our approach and targeted the PSA, which resulted in satisfactory control of the tremor. The permanent lead was implanted into the left side PSA. At 1-year follow-up, the right side tremor was under complete control.

Conclusion:

Our case and other similar pieces of evidence are consistently indicating the potential regulatory effects of PSA-DBS in controlling the Holmes tremor as a feasible alternative strategy when VIM-DBS does not provide a satisfactory response. However, further studies with larger sample size are required to evaluate the long-term response and its possible long-term stimulation-related effects.