An interventional study of MR-guided Focused Ultrasound Pallidothalamic Tractotomy and MR-guided Focused Ultrasound VIM Thalamotomy in Parkinson Disease (PD), sponsored by Research Center of Neurology, Russia. Not yet recruiting at 1 site in Russia. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-11-09.
Sponsored by Research Center of Neurology, Russia · Not applicable, Interventional, and Treatment
This study is evaluating MR-guided Focused Ultrasound (MRgFUS) treatment for people with Parkinson's disease (PD) who have disabling tremor, bradykinesia, and rigidity despite optimal medical therapy.
The study uses the Exablate Neuro System, which delivers ultrasound energy on a specific brain target and generates a small lesion (ablation) without making a surgical incision.
This study evaluates three treatment approaches targeting different brain structures involved in Parkinson's motor symptoms:
Participants will be randomly assigned to one of four groups: PTT, VIM, PTT+VIM, or "delayed treatment". Participants in the delayed-treatment group will continue best medical therapy for 6 months before receiving MRgFUS treatment.
The study aims to determine whether PTT provides greater improvement in motor symptoms than optimized medical therapy alone, whether adding VIM treatment to PTT improves tremor control, and whether adding PTT to VIM treatment provides additional improvement in bradykinesia and rigidity.
The main outcome measures are changes in the MDS-UPDRS Part III motor scores:
MDS-UPDRS Part III is a standard clinical scale used to assess Parkinson's motor symptoms. Assessments are performed in the OFF-medication state, meaning Parkinson's medications are temporarily withheld to better evaluate the treatment effect.
In addition, changes in motor complications, tremor severity, quality of life, and medication requirements will be assessed using MDS-UPDRS Parts II-IV, the Clinical Rating Scale for Tremor (CRST), the Parkinson's Disease Questionnaire (PDQ-39), and levodopa equivalent daily dose (LEDD).
Treatment-related adverse events, cognitive function, and ablation spot characteristics will also be evaluated throughout follow-up.
The trial is prospective, single-center, randomized and controlled, with four parallel groups and an overall allocation ratio of 2:2:2:1. Three active groups receive unilateral MRgFUS at PTT; VIM; or both targets (PTT+VIM in the same procedure). The fourth group continues BMT for 6 months before a second randomization (1:1:1) to one of the three MRgFUS target strategies. There is no sham procedure. The VIM arm is an active comparator, and the delayed-treatment arm permits evaluation against continued medication without controlling for placebo or expectancy effects. The protocol does not allow rescue lesioning of additional targets, such as the posterior subthalamic area, based on intraoperative response. Baseline and postoperative imaging includes high-resolution 3T MRI.
A statistician independent of recruitment, surgery and outcome assessment will generate stratified, variable-block randomization (blocks of 14 and 7) using a centralized web-based system. Allocation is disclosed to the surgical team immediately before preoperative planning and no later than 4 weeks before MRgFUS. Patients in the immediate-treatment arms will not be informed which anatomical target has been treated; the operator and surgical team cannot be blinded. Participants in the delayed-treatment arm know they are waiting for surgery. Clinical outcomes in all groups will be evaluated by an independent blinded neurologist. Part III of the MDS-UPDRS and the tremor rating scale will be videotaped for blinded central reassessment by two neurologists; rigidity requires in-person assessment.
Antiparkinsonian medication will remain stable for the first 6 months unless a change is clinically required. Scheduled visits include baseline, 1-3 days after surgery and 3, 6, and 12 months following the initial surgery; the delayed group is assessed at 3 and 6 months from randomization, then follows the postoperative schedule after later surgery. Clinical evaluations include MDS-UPDRS parts II-IV, Clinical Rating Scale for Tremor, MoCA, HADS, PDQ-39, levodopa equivalent daily dose and adverse event reporting. Motor outcomes are evaluated in medication-OFF state. Lesion volume, spatial accuracy, perifocal edema and sonication parameters will also be described.
An independent data and safety monitoring committee is planned. Its members will review serious adverse events and cumulative safety data at least every 6 months.
4,573 studies on the registry are indexed under Parkinson Disease; 1,086 are open to participants now.
This study's planned enrollment of 168 is above the median of 40 across 3,353 interventional studies indexed under Parkinson Disease.
Browse Parkinson Disease studies →Research Center of Neurology, Russia is the lead sponsor of 5 studies on the registry; 3 are open to participants now.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Short tests of memory and thinking, each scored out of 30. Lower scores suggest more difficulty; criteria give a range, either to include people with memory problems or to leave them out.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
MMSE and MoCA
Short tests of memory and thinking, each scored out of 30. Lower scores suggest more difficulty; criteria give a range, either to include people with memory problems or to leave them out.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
48 participants undergo unilateral MRI-guided focused ultrasound ablation of the pallidothalamic tracts in the Forel field region, contralateral to the more affected body side, with 5-7 planned thermal lesions. Optimized antiparkinsonian medication continues. Post-procedure follow-up: 1-3 days and 3, 6 and 12 months.
Procedure: MR-guided Focused Ultrasound Pallidothalamic Tractotomy · Other: best medical therapy
48 participants undergo unilateral MRI-guided focused ultrasound VIM thalamotomy using the institution's standard procedural method, contralateral to the more affected body side. Optimized antiparkinsonian medication continues. Post-procedure follow-up: 1-3 days and 3, 6 and 12 months.
Procedure: MR-guided Focused Ultrasound VIM Thalamotomy · Other: best medical therapy
48 participants undergo unilateral MRgFUS lesioning of both the pallidothalamic tracts and VIM within the same treatment session in a prespecified order. Optimized antiparkinsonian medication continues. Post-procedure follow-up: 1-3 days and 3, 6 and 12 months.
Procedure: Combined MR-guided Focused Ultrasound PTT and VIM Treatment · Other: best medical therapy
24 participants continue optimized antiparkinsonian medical therapy for 6 months after the initial randomization. They undergo blinded outcome assessment at 3 and 6 months without a sham procedure. After the month-6 assessment they undergo second randomization in a 1:1:1 ratio to PTT, VIM or combined PTT+VIM and then follow the active-procedure postoperative schedule. Early clinically indicated treatment is documented as an intercurrent event.
Procedure: MR-guided Focused Ultrasound Pallidothalamic Tractotomy · Procedure: MR-guided Focused Ultrasound VIM Thalamotomy · Procedure: Combined MR-guided Focused Ultrasound PTT and VIM Treatment · Other: best medical therapy
Unilateral MRgFUS thermal ablation in the region of the pallidothalamic tracts (ansa lenticularis and fasciculus lenticularis) within the Forel fields, approximately 5-7 lesions, using Insightec ExAblate 4000 Neuro. Targeting combines direct and indirect stereotactic navigation.
Unilateral thermal lesioning of the ventral intermediate nucleus of the thalamus by MRgFUS, using the center's prespecified standard technique and the Insightec ExAblate 4000 Neuro system.
PTT and VIM lesions made within one MRgFUS treatment session in a fixed sequence in accordance with a prespecified procedural SOP.
Continued individualized standard antiparkinsonian medication. The regimen is intended to remain unchanged for the first 6 months after randomization unless modification is medically indicated; all changes are recorded and the levodopa equivalent daily dose (LEDD) is calculated.
Change From Baseline in Contralateral MDS-UPDRS Part III ULE score in the OFF-medication at 6 Months (PTT vs Delayed Treatment)
Change in the summed Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III items for the ULE contralateral to the treatment side: limb rigidity, bradykinesia and tremor. Score range 0-40; higher scores indicate worse motor impairment. Evaluated in the practically defined medication-OFF state by an independent blinded neurologist. Primary contrast: PTT vs delayed medical treatment.
Time frame: Baseline and 6 months after initial randomization
Change From Baseline in Contralateral MDS-UPDRS Part III Tremor Sub-score in the OFF-medication at 6, 12 Months (PTT+VIM vs PTT)
Change in the sum of the contralateral tremor items from MDS-UPDRS Part III, score range 0-16; higher scores indicate worse tremor. Evaluated in the practically defined medication-OFF state by an independent blinded neurologist. Primary contrast: combined PTT+VIM versus PTT alone. Preoperative baseline is the reference assessment.
Time frame: Baseline, 6 months, and 12 months after initial MRgFUS treatment
Change From Baseline in Contralateral MDS-UPDRS Part III Bradykinesia and Rigidity Sub-score in the OFF-medication at 6, 12 Months (PTT+VIM vs VIM)
Change in contralateral limb rigidity and bradykinesia items on MDS-UPDRS Part III, score range 0-28; higher scores indicate worse motor impairment. Evaluated in the practically defined medication-OFF state by an independent blinded neurologist. Primary contrast: combined PTT+VIM versus VIM alone.
Time frame: Baseline, 6 months, and 12 months after initial MRgFUS treatment
Change From Baseline in Contralateral MDS-UPDRS III ULE score in the OFF-medication at 6, 12 Months (PTT vs VIM)
Change in the summed MDS-UPDRS Part III items for the ULE contralateral to the treatment side: limb rigidity, bradykinesia and tremor. Score range 0-40; higher scores indicate worse motor impairment. Evaluated in the practically defined medication-OFF state by an independent blinded neurologist. Key secondary prespecified PTT-versus-VIM contrast in medication-OFF state.
Time frame: Baseline, 6, and 12 months after initial MRgFUS treatment
Change From Baseline in Contralateral MDS-UPDRS Part III ULE score in the OFF-medication at 6 Months (VIM or PTT+VIM vs Delayed Treatment)
Change in the summed MDS-UPDRS Part III items for the ULE contralateral to the treatment side: limb rigidity, bradykinesia and tremor. Score range 0-40; higher scores indicate worse motor impairment. Evaluated in the practically defined medication-OFF state by an independent blinded neurologist. Two key secondary comparisons: VIM vs delayed treatment and PTT+VIM vs delayed treatment, medication-OFF state.
Time frame: Baseline and 6 months after initial randomization
Change From Baseline in Parkinson's Disease Questionnaire-39 Summary Index at 6 Months (PTT vs Delayed Treatment)
Parkinson's Disease Questionnaire-39 (PDQ-39) Summary Index, scaled 0-100; higher scores indicate worse health-related quality of life. Key secondary PTT-versus-delayed-treatment contrast.
Time frame: Baseline and 6 months after initial randomization
Change From Baseline in PDQ-39 Summary Index at 6, 12 Months (PTT vs PTT+VIM)
PDQ-39 Summary Index, 0-100; higher scores indicate worse health-related quality of life. Key secondary comparison of PTT with PTT+VIM.
Time frame: Baseline, 6, and 12 months after initial MRgFUS treatment
Change From Baseline in Total MDS-UPDRS Part III Score in Medication-OFF State
Total MDS-UPDRS Part III motor examination score, range 0-132, with higher values indicating worse motor impairment. Analyzed over follow-up visits; active groups' visits are measured from intervention.
Time frame: Baseline, 6, and 12 months after MRgFUS treatment
Change From Baseline in MDS-UPDRS Part II Score
MDS-UPDRS Part II assesses motor experiences of daily living. Range 0-52, with higher scores indicating worse symptoms.
Time frame: Baseline, 6, and 12 months after MRgFUS treatment
Change From Baseline in MDS-UPDRS Part IV Score
MDS-UPDRS Part IV assesses motor complications including fluctuations and dyskinesias. Range 0-24; higher scores indicate more severe motor complications.
Time frame: Baseline, 6, and 12 months after MRgFUS treatment
Change From Baseline in Contralateral Limb CRST Score
Sum of CRST items specific to limbs contralateral to the treated hemisphere, according to the prespecified CRST item mapping; higher scores indicate worse tremor. The exact item list and subscore range must be specified in the final scoring charter.
Time frame: Baseline, 6, and 12 months after MRgFUS treatment
Change From Baseline in Levodopa Equivalent Daily Dose
Total levodopa equivalent daily dose (LEDD), expressed in mg/day, calculated from all prescribed antiparkinsonian medicines using a prespecified conversion convention.
Time frame: Baseline, 6, and 12 months after MRgFUS treatment
Desirability of Outcome Ranking (DOOR) at 12 Months
Participant-level composite benefit-risk ranking (DOOR) based on efficacy and adverse-event outcomes. The ordered outcome categories, handling of death and missing information, and comparison statistic must be finalized prospectively in the statistical analysis plan.
Time frame: 12 months after MRgFUS treatment
Proportion of Participants With Persistent Procedure-Related Adverse Events at 12 Months
Number and percentage of treated participants with one or more adverse events judged related to MRgFUS that remain present at month 12; this is the key safety endpoint.
Time frame: From MRgFUS treatment through 12 months after treatment
Incidence, Severity and Duration of Treatment-Emergent Adverse Events
Number and percentage of participants with adverse events during the procedure, 1-3 days afterward and later through month 12; severity, causality and resolution are recorded. Events of special interest include gait/balance changes, dysarthria, dysphagia, paresthesia, weakness, memory problems and somnolence.
Time frame: During MRgFUS and up to 12 months after treatment
Change From Baseline in Montreal Cognitive Assessment Score
Montreal Cognitive Assessment (MoCA) total score, 0-30, with higher scores indicating better cognitive performance.
Time frame: Baseline, 6, and 12 months after MRgFUS treatment
Change From Baseline in Hospital Anxiety and Depression Scale Scores
Hospital Anxiety and Depression Scale (HADS) anxiety and depression subscales, each 0-21, with higher scores indicating greater symptom severity. Separate anxiety and depression results will be reported.
Time frame: Baseline, 6, and 12 months after MRgFUS treatment
Stereotactic Targeting Accuracy on Postoperative MRI
Euclidean distance (mm) between the planned geometric lesion center and the postoperative lesion center, with signed displacement along each stereotactic axis.
Time frame: Preoperative planning and postoperative MRI at 1-3 days after MRgFUS
Plan to share: Undecided — The protocol does not currently specify whether de-identified individual participant data and supporting documentation will be shared with external researchers. A data access and confidentiality policy will be determined by the study sponsor and ethics/regulatory authorities before the final registration update.
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Research Center of Neurology, Russia