Focused ultrasound ablation is associated with substantial and sustained improvements in motor symptoms for Parkinson’s disease patients, new research suggests.

The study, funded by Insightec, found that staged bilateral ablation with magnetic resonance-guided focused ultrasound (MRgFUS) improved motor symptom scores by 67% three months after treatment, with benefits maintained through to 12 months.

However, while unilateral ablation offered excellent safety and sustained benefits, the second bilateral procedure resulted in a high burden of moderate and severe adverse events.

As such, a UK expert commenting on the study suggested that bilateral MRgFUS should not yet be adopted in routine practice.

The study

In the study, published in The Lancet Neurology [link here], 54 Parkinson’s disease patients at nine centres across the USA, Spain and Taiwan underwent unilateral MRgFUS pallidothalamic tractotomy to the symptom-dominant side with Insightec’s Exablate Neuro system.

Three months after unilateral treatment, off-medication treated-side upper and lower extremity motor scores showed a 53% median within-patient improvement (median 20 to 9.5 points, p<0.0001).

A further 40 of these patients then underwent contralateral pallidothalamic tractotomy a minimum of six months later (median interval 189 days).

Three months after the second treatment:

• Patients’ off-medication upper and lower extremity motor scores for both sides combined showed a median within-patient improvement from baseline of 32% (p<0.0001).
• Total motor score also improved by 67% at three months, with benefits sustained through to 12 months.

After the unilateral procedure, 21 patients (39%) experienced treatment-related adverse events, of which 87% were mild and 13% were moderate, with one (2%) persistent moderate adverse event at six months.

After bilateral treatment, 22 (55%) of 40 patients experienced treatment-related adverse events (70% mild, 28% moderate, 2% severe) and ten (25%) had persistent moderate or severe adverse events at 12 months, mainly affecting speech, gait, and balance, with one patient developing severe persistent anarthria.

“This study gives us the evidence-based guidance we’ve been waiting for, demonstrating that focused ultrasound treatment can deliver meaningful, lasting relief for Parkinson’s that builds with each procedure,” said lead author Dr Arif Dalvi, director of the Comprehensive Movement Disorders Center at Palm Beach Health Network, Florida, USA.

“Importantly, it expands the role of this treatment beyond tremor, to address the motor fluctuations and involuntary movements that make daily life so difficult in later-stage Parkinson’s,” he added.

Evidence not yet strong enough for routine bilateral use

In an accompanying editorial [link here], Professor Ludvic Zrinzo, a consultant neurosurgeon at the UK National Hospital for Neurology and Neurosurgery, wrote that the findings “support cautious optimism that unilateral focused ultrasound pallidothalamic tractotomy (FUSPTTy) could provide a safe, durable, and effective therapeutic option, especially for patients with marked asymmetry of symptoms.”

However, he said that the results did not support routine use of bilateral FUSPTTy, citing the modest impact of additional improvement from the second procedure, as well as the high burden of moderate-to-severe adverse events one year after treatment, despite careful patient selection.

“Dalvi and colleagues suggest that similar complications can follow deep brain stimulation (DBS); crucially, however, DBS permits titration of stimulation to minimise side-effects while still providing therapeutic benefit, an option unavailable after ablation,” he wrote.

Professor Zrinzo also noted that a questionnaire administered by the FDA showed that, three months after the second procedure, 35% of patients would not choose to undergo it again.

“Such a high proportion of patients unwilling to repeat the procedure is striking and warrants scrutiny, particularly because it remains unclear whether this finding reflected insufficient benefit, persistent adverse effects, or both,” he wrote.

While “unilateral FUSPTTy appears to offer a promising, safe, and potentially durable therapeutic option,” he suggested that “the role of staged bilateral FUSPTTy remains uncertain, given its diminishing returns and significant risk of moderate-to-severe side-effects.”

“Whether more rigorous patient selection and refined surgical targeting will improve the risk–benefit profile of bilateral FUSPTTy remains to be seen,” he concluded.