Brain surgery and sound waves prove safer than expected

A new study of patients undergoing ultrasound surgery on both sides of the brain showed a surprisingly minimal cognitive effect, challenging the long-term fear of bilateral brain surgery.

The study involved 21 patients with severe intrinsic tremors and found that 95% of cognitive test scores remained stable after the second side surgery, and only 2% showed a decline. This represents the largest and most comprehensive cognitive assessment of bilateral ultrasound psychological systomy to date, providing new hope for patients whose tremors have not yet responded to medication.

These findings address a key problem that patients with basic tremor have limited treatment options, often facing difficult choices between suffering from symptoms of debilitation and the possibility of risking the potential cognitive consequences of bilateral brain interventions.

When the drug fails

Basic tremors affect approximately 1% of the global population, making it one of the most common dyskinesia. While this condition mainly causes movement vibrations in the arms and hands, severe cases can destroy daily activities such as diet, drinking and writing, resulting in social isolation and a reduced quality of life.

Traditional treatment begins with drugs such as beta blockers and resistant drugs. However, a large percentage of patients either fail to achieve sufficient tremor control or experience unbearable side effects, so they have few choices other than neurosurgical interventions.

Focused ultrasound psychological incision has become an accurate, minimally invasive alternative to traditional brain surgery. The technique uses concentrated sound waves to create small, controlled lesions in the ventral intermediate nucleus of the thalamus, a brain region that regulates movement when overactive in patients with essential tremors.

Bilateral Challenge

Although the FDA approved unilateral ultrasound tremor in 2016, bilateral treatment remains more controversial. Historical experience with traditional bilateral thalamic surgery procedures shows that the risk of speech and cognitive problems has increased, leaving doctors cautious about both parties treating the brain.

The FDA approved bilaterally focused ultrasound to reignite interest in both brain hemispheres in December 2022, but evidence on cognitive safety remains limited. Previous studies suffered from small sample sizes (usually less than 12 participants) or rely on brief cognitive screening tests that may miss subtle but important changes.

How do you balance the potential advantages of improving tremor control with unknown cognitive risks? This problem puts many patients and doctors in a difficult position, especially when tremors severely affect hands.

Comprehensive cognitive testing

To date, the Toronto-based research team conducted the most thorough cognitive assessment, testing 21 patients about four months after the second side surgery. All participants previously received successful unilateral treatment at least a year ago.

Neuropsychological batteries are specifically designed to minimize exercise requirements while evaluating multiple cognitive areas:

• Global awareness and attention – Including concentration and working memory tasks
• Processing speed – How quickly can patients complete psychological tasks
• Execute functions – Planning, inhibition and psychological flexibility
• memory – Immediate and delayed recall capability
• Language skills – Word fluency and naming ability
• Visual Space Processing – Spatial reasoning and visual perception

Importantly, the researchers analyzed the results of group-level and individual analyses, allowing them to detect changes in specific patients who may be masked by the overall mean, a crucial methodological advance that provides more detailed insights into cognitive safety.

Significant stability

The results proved to be assured across multiple measures. At the group level, no cognitive tests showed a statistically significant decline after considering multiple comparisons. Even for tests that initially seemed to show a decline (color naming task), involving a median increase in completion time by one second, no individual patients showed a reliable decline in this measure.

Individual-level analysis reveals more compelling evidence of cognitive safety. Of the 371 individual test scores analyzed by all patients, 94.6% were stable, 3.5% improved, and only 1.9% decreased by 1.9%. In more than two cognitive tests, no patients declined, and no single test showed a decline in more than two patients.

Perhaps most importantly, three patients with mild cognitive impairment showed similar stable patterns, with 94.4% of the test scores remaining unchanged, while in all three patients, only one point was decreasing in total.

Reliable innovation and innovation

The complex statistical method of this study represents a significant advance in evaluating cognitive outcomes. The researchers not only rely on population mean, but calculated a reliable index of change for each patient, an approach that distinguishes true cognitive changes from normal measured variability or practical effects.

This individual-level analysis proved to be crucial because it reveals that obvious stability at the group level does not mask the widespread individual decline. If the program caused real cognitive problems, the researchers would have expected to see a systemic decline in many patients – a pattern that didn’t appear at all.

Drug analysis provides additional assurance. Throughout the study period, most patients either maintained tremor medication or maintained a stable dose, while those who lowered medication did not show a consistent pattern of cognitive change, suggesting that cognitive stability is not just due to drug effects.

Clinical impact and limitations

As expected, the patient’s treatment hands showed significant improvement in tremor, with the tremor score on the clinical score scale dropping from 18.2 at baseline to 8.9 at follow-up. This reduction in tremor, coupled with cognitive safety findings, suggests that bilateral focus on bilateral ultrasound can provide meaningful benefits without historically associated cognitive costs with bilateral brain intervention.

However, researchers acknowledge important limitations. This study may represent the best outcome, as only patients who had no major problems in the first surgery received second-side treatment. The sample was also mostly white and well-educated, which may limit the generality to a wider population.

The relatively small number of patients with mild cognitive impairment means more research is needed to understand the safety of this vulnerable population. Furthermore, the four-month follow-up period although the standard time of such studies did not capture potential long-term cognitive changes.

Change the therapeutic landscape

These findings can fundamentally change the treatment discussions in patients with basic tremors. Historical fear of bilateral brain procedures makes many patients limited choices when unilateral treatment provides insufficient benefits. Bilateral attention to cognitive decline after ultrasound is neither consistent nor universal proof, opening up new possibilities for more complete tremor control.

The study also validates the precise advantage of centralized ultrasound over traditional surgical methods. While minimizing damage to surrounding brain tissue, the ability to minimize damage to surrounding brain tissue is translated into meaningful clinical benefits in terms of cognitive preservation.

For millions of people worldwide who are estimated to live in drug-refractory basic tremors, these results offer hope that effective treatments do not require a choice between tremor control and cognitive function, a wrong choice with limited treatment options for too long.

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