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Essential tremor - Ultrasound thalamotomy

MR guided Focused Ultrasound Thalamotomy (FUS) for essential tremors

What is MR Guided focused ultrasound treatment?

Most people are familiar with ultrasound scans being used to “see” structures inside the body including unborn babies inside the womb. These same sound waves are applied in focused ultrasound (FUS) to deliver packets of energy to the brain to treat tremors. This technology uses multiple sound waves at a high frequency focused in on one spot deep within the brain. The multiple sound waves intersect at a point in the brain, guided by MRI scan images, where it generates heat and causes very targeted thermal damage to an area in the brain called the thalamus, the result of which is improvement in tremors .The advantage of this procedure is that FUS harnesses the power of ultrasound waves to reach deep brain regions without the need for cutting into the skull or the brain as is usual in brain surgery.

What happens during the procedure?

During the procedure, a special head frame is fitted to the patient’s head with local anaesthetic. This will attach to a focused ultrasound helmet that helps to hold the patient’s head still during the procedure. Once the frame is fitted, the patient is moved into an operating theatre with an MRI suite (magnetic resonance imaging) where they will move in and out of the MRI scanner so that real-time, accurate targeting of the correct region can be undertaken and based on the images, ultrasound waves are focused on to the brain in a targeted way to induce thermal damage. Even though the procedure involves no incision or drilling, it does result in thermal damage to an area of the brain called thalamus. Thalamus is part of the brain network which helps with fine and precise movements and has long been recognised to play a role in the genesis of tremors and has been a target of treatment for improving tremors for several decades.

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(4-6 hours typically), the benefits can be felt immediately. Patients are usually able to go home the same day or the day after. Most return to activities of normal life within several days.

Who is eligible for this treatment?

Currently this is licensed to treat a condition called essential tremors. Patients with other forms of tremors are not eligible for this treatment at this point. The treatment is only undertaken in one half of the brain and so will only provide relief from tremors on one side of the body.

Who cannot have this treatment?

Patients should be able to have MRI scans safely to undergo this procedure. Patients who have pacemakers even if they are MRI compatible cannot undergo the procedure. Patients with dementia or other severe memory problems, gait problems or speech impediments are unable to have this procedure safely and if you are referred for the procedure, you will be carefully screened for such contraindications before undergoing the procedure.
Patients who are on blood thinners will need to temporarily stop the treatment before undergoing the procedure.

What are the common side effects?

Temporary or permanent neurologic deficits can occur following treatment. It is very common for patients to feel dizziness or pressure inside the head during the treatment and this is short lived. Side effects which can occur after the procedure can include walking disturbances , imbalance, numbness and speech disturbances. Most of the side effects are temporary and usually occur due to underlying brain swelling which resolves within a matter of days, but some of the side effects can be permanent and this can occur in up to 10% of patients undergoing the procedure.

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