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 halamotomy, which will be discussed later in this handbook, 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 Neuravive procedure.

Pre-Op
The patient has their head shaved and wears a stereotactic frame similar to the one described in the DBS section above. Transducers in the frame 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.

Procedure
With the frame in place, patients are moved into an MRI (magnetic resonance imaging) machine, where they remain for the entire 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. And although the process takes several hours, the benefits can be felt immediately. There is virtually no downtime and patients are usually able to go home the same day. Most return to activities of normal life within 24 hours.

Considerations
Even though the procedure is transcranial and involves no incision or drilling, it does create a thalamic lesion, which destroys a part of the brain and can result in permanent neurologic deficits. Initial study results indicated that of the 76 ET patients who received the treatment, 74 neurologic adverse events were reported in 56 of the people treated. The most common side effect was an alteration in sensation, which was reported by 38% of the patients and persisted at 12 months in 14%. Gait disturbance occurred in 36% of patients and persisted at 12 months in 9%. The incidence of cerebellar deficits such as dysmetria (coordination issue where movements undershoot or overshoot intended position), ataxia (loss of full control of bodily movements, often affecting walking and balance), and unsteadiness of gait approached 5% each at 12 months.

As this is a new procedure, there are no statistics on the long-term effectiveness (beyond 12 months) of this treatment. Patients who participated in this original study, however, will continue to be followed by researchers for five years.

Outcomes
Focused ultrasound has been reported to have a 47% improvement in targeted hand tremor after three months and a 40% improvement one year after surgery. 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. It 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 several academic medical centers in North America, Europe, and Asia.

Other Uses
Research is ongoing to expand 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.