Focused Ultrasound vs. DBS for Parkinson Disease: What New Bilateral Data Tell Us

A prospective, multicenter study published in The Lancet Neurology offers the most complete picture yet of how staged bilateral MRI-guided focused ultrasound pallidothalamic tractotomy performs over time in patients with Parkinson disease (PD) motor complications. The trial enrolled 54 patients across nine centers, with 40 proceeding to bilateral treatment, and followed participants through 12 months after the second procedure. Key findings included a 66.8% improvement in motor complications at three months, a dramatic reduction in dyskinesia, and benefits that held through the full follow-up period, though bilateral treatment raised the rate of persistent speech, gait, and balance side effects to 25%.¹

The study represents the exact dataset reviewed by the FDA in its July 2025 approval of staged bilateral focused ultrasound for advanced PD, expanding access for an estimated 1.2 million Americans projected to be living with the disease by 2030. In a follow-up, NeurologyLive spoke with Arif Dalvi, MD, a study investigator and Director of the Comprehensive Movement Disorders Center at Palm Beach Health Network, to discuss the clinical implications of the findings.

In this Q&A, Dr. Dalvi walks through the durability data, how focused ultrasound compares to deep brain stimulation, what the right patient profile looks like for staged bilateral treatment, and what questions remain heading into the next phase of research.

NeurologyLive: Can you summarize the key findings from this study, particularly the durability of benefit following staged bilateral focused ultrasound through 12 months?

Arif Dalvi, MD: The trial was designed to follow patients closely over a period of 12 months. Each person was first treated on the more affected side, observed for a minimum of six months, and then, if they qualified, treated on the second side and followed for a further 12 months. That gives us one of the most complete pictures available of how MRgFUS performs over time.

In patients treated on just one side, motor complications dropped by two-thirds within three months, and dyskinesia fell sharply to under a fifth of patients by six months, disappearing entirely once the second side was treated. That benefit held steady for a full year, with a 98% clean safety record.

Adding the second side gave patients meaningful additional motor improvement on top of that first-side benefit, and those gains also held through 12 months of follow-up. There was a trade-off in that treating the second side raised the rate of persistent speech, gait, and balance side effects to about 25%.

Because Parkinson disease typically affects one side of the body more than the other, a one-sided procedure alone already offers most patients a real chance at robust motor improvement and a dramatic reduction in fluctuations and dyskinesia. Whether to move forward with the second side is a separate, careful decision, and one that requires a detailed evaluation of speech, gait, and balance before proceeding.

How do these data build upon the FDA's approval of staged bilateral focused ultrasound, and what additional confidence do they provide regarding the safety and efficacy of treating both sides?

This paper is the exact dataset the FDA reviewed in approving staged bilateral pallidothalamic tractotomy last year. What we were able to demonstrate to the FDA was that unilateral treatment is remarkably safe and effective, and that bilateral treatment adds real, measurable motor benefit on top of that. We also clarified through the paper that the second side raises the chance of a lasting speech or gait issue from 2% to 25%. We need to counsel patients thoroughly on this increased risk and reevaluate them fully in terms of speech, gait, and balance before recommending the second-side procedure. That is exactly the kind of evidence clinicians need to use this data responsibly rather than reflexively.

For patients with PD experiencing disabling motor fluctuations or dyskinesias, how should clinicians think about focused ultrasound relative to established device-based therapies such as deep brain stimulation?

For patients who are hesitant about brain surgery, incisions, or living with implanted hardware, focused ultrasound is an incredibly appealing option. The procedure is a same-day outpatient procedure, and most patients return home the same day already showing improvements to the treated side. There is no burr hole drilled in the skull, no pacemaker device to be implanted, and no need for battery changes or recharging. Unilaterally, the results rival anything we see with DBS.

While bilateral speech and balance risks are higher, they are in the same ballpark as what has been reported for bilateral DBS, as we discuss in the paper. So this is not a case of focused ultrasound being the riskier choice. It is that treating both sides of the brain, with any technology, carries a cumulative cost. Patients now have a genuine additional option, and the choice comes down to invasiveness versus reversibility. Centers such as ours at Delray Medical Center offer both procedures, and we include patients and their families in making the decision that best suits their disease state and preferences.

What have you learned about patient selection for staged bilateral treatment, and which clinical characteristics are most important when determining candidacy?

The ideal candidate has idiopathic Parkinson disease, with atypical parkinsonian syndromes carefully excluded through prior workup, and disabling dyskinesia or motor fluctuations. They need to demonstrate a strong response to levodopa, usually measured with an off-on levodopa evaluation, and the right skull characteristics, specifically skull density ratio, for the technology. The patient only moves forward with the second side if they come through the first completely clean, with no lingering speech, swallowing, or gait problems. We reserve the second side for patients whose remaining symptoms are disabling enough to justify that added, irreversible risk, after a very candid conversation regarding the risks involved.

Looking ahead, what unanswered questions remain regarding bilateral focused ultrasound, and what additional evidence would you like to see to further define its role in Parkinson disease management?

One big question is whether we can keep the motor benefit of bilateral treatment while bringing that complication rate down. Our team has been in discussions planning follow-up clinical trials to build on this success, aiming for even better clinical outcomes, whether through refined targeting, smaller ablation volumes, or lower energy. We also want randomized, sham-controlled trials, a more diverse patient population than this first cohort, and a clearer picture of how outcomes evolve as more centers move past the early learning curve. This trial proves the concept works remarkably well on one side. The goal for the next phase is optimizing the second-side surgery.

Transcript edited for clarity.

REFERENCE
Dalvi A, Eisenberg HM, Wu P, et al. Safety and efficacy of staged, bilateral magnetic resonance-guided focused ultrasound pallidothalamic tractotomy for motor complications of Parkinson's disease: a prospective, multicentre, single-arm trial. Lancet Neurol. 2026;25(7). doi: 10.1016/S1474-4422(26)00142-0