Focused Ultrasound Unilateral Pallidotomy for Medication-Refractory Limb Dystonia

The FUTURE study is a prospective, randomized, double-blind, sham-controlled, multicenter national clinical trial aimed at assessing the efficacy and safety of unilateral MR-guided focused ultrasound (MRgFUS) pallidotomy in patients with limb dystonia that is refractory to standard pharmacological treatments.

Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions, causing abnormal movements or postures. In many cases, focal or segmental dystonias affecting the limbs can be managed with oral medications and botulinum toxin (BoNT) injections. However, a subset of patients does not respond adequately to these treatments. For such individuals, surgical intervention may offer relief, yet it remains underutilized due to concerns about invasiveness and complications.

Recent advancements in non-invasive neurosurgical techniques have introduced MRgFUS pallidotomy, a procedure that uses focused ultrasound beams under real-time MRI guidance to precisely ablate small brain targets-in this case, the globus pallidus internus (GPi). The FUTURE study specifically explores this technique as a less invasive alternative to deep brain stimulation, especially for patients with focal or segmental limb dystonia who are ineligible or reluctant to undergo conventional surgery.

The trial will enroll 34 adult patients with idiopathic or genetic limb dystonia that has proven resistant to pharmacologic and BoNT treatment. These patients will be randomly assigned in a 1:1 ratio to either:

• an active treatment group, undergoing unilateral GPi lesioning via MRgFUS,
• or a sham control group, receiving the same procedural setup but without therapeutic sonications.

At three months post-randomization, all patients in the sham group will cross over to receive the active MRgFUS treatment, allowing within-subject comparisons while ensuring ethical access to the therapeutic intervention. The follow-up period for each patient will last six months after active treatment, totaling a maximum of nine months of participation.

The primary endpoint is the change in motor severity as measured by the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) at three months post-treatment. Secondary endpoints include adverse event frequency, patient and clinician global impressions of change, disability assessments (e.g., QuickDASH), quality of life (SF-36), and neurocognitive testing.

Additionally, the study will incorporate neurophysiological (TMS) and neuroimaging (resting-state fMRI) techniques to investigate treatment-induced changes in cortical excitability, plasticity, and functional connectivity, providing insight into the neural mechanisms underlying clinical improvement.

The FUTURE study is coordinated by the Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy with participation from other three major Italian neurological institutes. It represents a pioneering effort to evaluate focused ultrasound as a non-invasive therapeutic option for patients with disabling and treatment-resistant forms of limb dystonia.

Inclusion criteria

• Age 18-80 years
• Able and willing to consent and attend visits
• Idiopathic or hereditary limb dystonia (focal, segmental, or multifocal; isolated or combined)
• Refractory to oral therapy and botulinum toxin
• Stable medication for ≥30 days and ≥90 days since last BoNT
• Capable of communicating during Exablate procedure

Exclusion criteria

• Acquired secondary dystonia
• Dementia or other neurodegenerative disorders
• Any clinically significant or unstable medical condition, which, in the opinion of the principal investigator or the clinician delegated by the principal investigator, may put the participant at risk when participating in the study (e.g., unstable heart disease or coagulopathy; uncontrolled psychiatric comorbidity)
• Prior deep brain stimulation or other brain surgery
• Any contraindication to MRI
• Skull Density Ratio (SDR) < 0.40
• Significant brain lesions (eg brain tumor, significant white matter lesions or globus pallidus interna lesions on baseline MRI)
• Pregnancy