Researchers at the UT Southwestern have published promising results in the journal Brain of using a new four-tract tractography method to personalize MRI-guided, high-intensity focused ultrasound (HIFU) to treat medication refractory tremor in essential tremor and tremor-dominant Parkinson’s disease. Clinical result from the use of the method indicates it could enable more precise targeting of the brain with improved treatment responses, while also reducing treatment times and side effects.
“Historically, the target for tremor could not be seen on standard high-resolution magnetic resonance images, so landmark-based methods have been used,” said corresponding author Bhavya R. Shah, MD, and assistant professor of Radiology and Neurological Surgery and investigator in the Peter O’Donnell Jr. Brain Institute at UT Southwestern Medical Center. “By using tractography and other advanced magnetic resonance methods, we are working to identify the precise location of the target in individual patients and improve patient outcomes.”
The U.S. Food and Drug Administration has previously approved the use of MRI-guided HIFU ablation of the ventral intermediate nucleus of the thalamus for the treatment of essential tremor and tremor-dominant Parkinson’s disease. However, the efficacy and safety of this form of treatment relies on direct targeting that MRI can not currently provide. Instead, targeting techniques rely on indirect methods using landmarks to identify the correct region. This indirect targeting method can sometime result in serious side effects after treatment that include weakness, numbness, and paresthesia in one-third of patients. These adverse events might otherwise be averted by the use of more direct targeting techniques that can precisely target the region most effective for treatment, while identify areas to avoid.
To develop a more targeted method, the UT Southwestern researchers improved the standardized four-tract tractography for HIFU using an FDA-approved surgical planning software that should allow this method to be easily implemented in the clinical setting. The current work by Shah and colleagues builds on his 2020 publication in Brain that detailed the feasibility of standard MRI techniques to identify tremor-associated white-matter tracts.
The latest research included 18 patients who received MRI-guided HIFU and had at least three months of follow-up post-treatment. None of the patients experienced the typical post-treatment side effects of current methods—weakness, numbness, or paresthesia—suggesting the new method decreases side effects. Three patient did experience transient (three weeks) imbalance, which is common after magnetic resonance-guided HIFU.
While the study had limitations including treatment of all patients at a single center with a short follow up time, even with its small size, the data were strong enough to suggest further study of the method in a broader population.
To this end, a multicenter trial is planned with other U.S. sites, including the University of California San Francisco, the Mayo Clinic in Rochester, Minnesota, the University of Colorado, and an international site in Spain. The hope is that further study of the method will yield more personalized treatment of patient with essential tremor and tremor-dominant Parkinson’s disease.