Focused Ultrasound Thalamotomy

The FDA approved a new treatment for ET in 2016 – it’s called focused ultrasound. Now, this surgical option is available in the U.S., Canada, and many other parts of the world. Although similar to radiosurgical thalamotomy, focused ultrasound utilizes sound waves rather than radiation to destroy brain tissue within the VIM nucleus, thus stopping tremor.

Most people are familiar with ultrasound being used to “see” unborn babies inside the womb. These same sound waves are applied in focused ultrasound but in a very different way. This technology uses multiple beams of sound focused in on one spot deep within the brain. The point of intersection of these sound waves generates heat, much like how a magnifying glass focuses beams of sunlight to burn a hole in a leaf. Learn more about the procedure.

The patient has their head shaved and wears a stereotactic frame similar to the one described in the DBS section above. The patient then lies down with their head in a helmet which contains the transducers that deliver the ultrasound waves to the brain. The individual sound waves safely travel through the skin, skull, and brain until they converge at the target tissue. The destruction of the target tissue interrupts circuits of the brain responsible for tremor.

With the frame in place, patients are moved into an MRI (magnetic resonance imaging) room, where they will move in and out of the MRI scanner  for the procedure. MRI allows the surgeon to see the brain in real-time, validate they are targeting the correct region, and monitor the exact amount of heat being applied (approximately 55- 60°C/131-140°F).

Patients are fully awake during the procedure, interacting with the medical team as they assess progress in reducing tremor throughout the process . In addition, the target can be adjusted if the patient reports any potential side effects or other sensations. And although the process takes several hours, the benefits can be felt immediately. Patients are usually able to go home the same day. Most return to activities of normal life within several days.

Even though the procedure involves no incision or drilling, it does create a thalamic lesion, which destroys a part of the brain and can result in temporary or permanent neurologic deficits. Three-year follow up of the clinical study includes 54 subjects.  

At three-year follow-up, 56% of the adverse events still ongoing were mild and the remaining were moderate and included gait disturbance (2%), imbalance (4%), musculoskeletal weakness (2%), unsteadiness (4%) and numbness (9%). The number in parenthesis is the percentage of active subjects experiencing these adverse events. The majority of all adverse events began within 30 days of the procedure and nearly all resolved.

As this is a fairly new procedure, the data presented here is at three-years following the treatment. Patients who participated in this original study will continue to be followed by researchers for five years.

The outcomes of the INSIGHTEC sponsored clinical trial demonstrated an average 76.5% improvement in tremor severity at 3-year follow up in 54 subjects [Pre-Market Approval (PMA) P150038].

A three-year analysis of long-term results showed individuals’ hand tremor severity scores improved by 76.5% over baseline. Improvement in tremor/motor function after three years was 53%. Read the latest report on outcomes here. Focused ultrasound offers a reduced risk of infection and blood clot formation, and there is no exposure to radiation. It also offers tremor relief without the need for periodic equipment adjustments. However, treatment is currently considered safe to treat just one side of the brain, usually the dominant side.

Focused ultrasound is currently available to treat ET at a growing list of medical centers in North America, Europe, and Asia.

Other Uses
Research is ongoing to evaluate the use of this technology to treat patients with other neurological disorders, including Parkinson’s disease, epilepsy, brain tumors, obsessive-compulsive disorder, depression, dystonia, and Alzheimer’s disease.

For more information, download the Surgical Options Guide.