The short version
- Focused ultrasound aimed at one side of the brain cut Parkinson’s motor complications with very few lasting side effects in a 54-person trial.
- Treating the second side six months later improved the trial’s main motor score by 32%, but 25% of those patients had moderate or severe speech, gait or balance problems a year on.
- The FDA approved the two-sided procedure in 2025 for carefully chosen patients, and Medicare has covered it since March 2026.
A beam of sound can quiet Parkinson’s symptoms on one side of the body without a single incision. A multicentre trial in The Lancet Neurology asked what happens when you do it twice. The answer: a second treatment adds a modest gain and a real risk.
The procedure
MRI-guided focused ultrasound brings sound beams together on a point deep in the brain and ablates the tissue there, with no incision and no implanted hardware. This trial aimed at the pallidothalamic tract, a bundle of fibres carrying signals from the globus pallidus interna to the thalamus. The device is Insightec’s Exablate Neuro. Insightec funded the study.
Lesioning one side of this circuit eases symptoms on the opposite side of the body. Parkinson’s affects both sides. Until now, though, no prospective multicentre trial had tested a staged second lesion.
The design
Nine centres took part: six in the US, two in Spain and one in Taiwan. They enrolled 54 adults whose Parkinson’s still responded to levodopa but who had motor complications: off periods when the drug wears off, and dyskinesia, the involuntary movements it can cause. Everyone was treated first on the side of the brain driving their worse symptoms. At least six months later, those who met preset criteria could have the other side treated. Forty did, and 36 of them completed a year of follow-up.
The main measure was the change in arm and leg scores on the standard Parkinson’s motor exam (MDS-UPDRS part III), taken off medication, three months after the second procedure. There was no sham group. Everyone knew they had been treated.
The results
Benefit showed up within a month of the first treatment. Three months after the second side, the median arm-and-leg score had dropped from 33 to 21, a 32% improvement. Lead author Arif Dalvi told NeurologyLive that dyskinesia was present in under a fifth of patients six months after the first side.
According to the FDA’s review, as described in Weill Cornell’s release, 86% of patients reported at least some improvement three months after the second procedure, and 62% said they were satisfied with it.
The side effects are where the two treatments part ways. After one side, 39% had a treatment-related adverse event, and only one person (2%) had a moderate problem that persisted. After the second side, 55% had an adverse event. A year later, 10 of the 40 (25%) still had moderate or severe problems, mostly with speech, walking and balance. One person (3%) lost the ability to articulate speech.
The authors’ own reading is blunt. The first treatment was safe and helpful. The second gave small extra motor gains at the cost of more lasting harm, and needs careful selection and frank counselling about cumulative risk.
The limits
This was a single-arm trial, so some of the improvement may reflect patients’ and examiners’ expectations. A sham-controlled trial would settle that. The manufacturer paid for the study. A year is short for a progressive disease. And there was no head-to-head comparison with deep brain stimulation (DBS), the implanted-electrode alternative. Dalvi says the two-sided risks are “in the same ballpark” as those reported for bilateral DBS, but that comparison crosses different studies.
The paper came out in July. Weill Cornell’s release on October 27, from the team of co-lead Michael Kaplitt, brought it back into the news.
Why it matters
The FDA approved staged bilateral treatment in July 2025, and Medicare began paying for it in March 2026. That makes this the evidence patients and neurologists are now weighing. The FDA’s advice tracks the data: reserve the second side for people with disabling symptoms on the untreated side who had no serious side effects the first time.
The first side looks like the strong part of the story. The second is a trade some patients will choose and others will reasonably decline.
What to watch: longer follow-up from this cohort, and any sham-controlled or DBS-comparison trial of the second side. Low-intensity ultrasound, which modulates rather than destroys tissue, is being tested in other conditions, such as the schizophrenia pilots we covered yesterday.
