Focused ultrasound is an incision-free, minimally invasive treatment for essential tremor, a neurological condition that causes uncontrollable shaking, most often in the hands, head or voice. Essential tremor is the most common movement disorder, affecting an estimated 10 million Americans. For some people, the shakiness is so severe that it impedes their ability to function. Although the cause is not well understood, research has shown that the tremor can be alleviated by treating a small area deep inside the brain that regulates movement; this tiny area is the ventral intermediate (Vim) nucleus of the thalamus.
During this outpatient procedure, high-intensity sound waves, guided by MRI, are focused on the Vim. These sound waves pass painlessly and safely through skin, bone and brain to reach their target. Much as a magnifying glass can focus sunlight to burn a hole in paper, the focused ultrasound generates enough heat to burn cells in the Vim without harming surrounding tissue. Recovery time is short, and the treatment can significantly reduce tremor, improving the ability to perform daily activities, such as eating, drinking and writing. It does not, however, cure the underlying disease.
Targeting the same area of the thalamus, focused ultrasound can also be used to treat tremors for patients with tremor-dominant Parkinson's disease. UCSF doctors are at the forefront of investigations into the use of focused ultrasound to treat other conditions, including brain tumors and prostate cancer.
Who may benefit
The treatment is for people with a confirmed diagnosis of essential tremor that hasn't responded to medications. Patients must be over the age of 22.
Focused ultrasound has many advantages over other treatments, including:
- It doesn't require traditional surgery. There's no incision or opening of the skull, reducing the risk of infection.
- It precisely targets the area of the brain implicated in tremors without harming surrounding healthy tissue.
- It's an outpatient procedure with a short recovery time.
- Most patients experience an immediate and significant reduction in tremors. The effect can last as long as three years.
- Patients aren't exposed to radiation.
To be eligible for this treatment, you must have a confirmed diagnosis of essential tremor, usually based on a neurological examination. You'll also need to have tried at least two prescribed tremor-controlling medications without success. You'll have a CT scan to determine whether your skull's shape and thickness are suitable for focused ultrasound. (Some skull features prevent the focused ultrasound from reaching the target tissue with enough heat to be effective.) It's also important that you feel comfortable lying still in an MRI scanner for the two to three hours that the procedure requires.
The procedure is performed while you're in an MRI scanner. Before you get into the machine, we will shave your head to ensure hair doesn't obstruct the sound waves. You will wear a silicon cap that allows cool water to circulate, protecting your scalp from the ultrasound's heat, and we'll secure your head in a frame that prevents it from moving during the procedure.
You'll be awake and able to communicate with us. We will be in a room next to the MRI suite, planning and performing the procedure from a computer. We will take MRI scans of your brain to precisely locate the target area and then give small doses of ultrasound energy to confirm the target. Once we're confident of the location, we will increase the focused energy to have a permanent effect on the targeted area.
We'll be monitoring your vital signs and brain temperature. At times during the procedure, your doctor will ask you questions and have you perform tasks such as moving your hand, holding objects or writing; this helps us evaluate whether the tremor is lessening. While the treatment is generally painless, some people experience mild headache, dizziness and nausea. These sensations usually go away shortly after treatment.
When the procedure is complete, you'll move to a recovery room. Most patients are able to go home the same day. Your doctor will let you know when to return for any follow-up visits.
Some patients experience headaches, nausea or problems with balance during or right after treatment. These effects usually resolve quickly. Most patients are able to return to work and their normal activities within several days.
Complications and side effects are uncommon but can include:
- Temporary or permanent muscle weakness
- Unsteadiness when walking
- Sensory loss
- Numbness or tingling in the fingers or elsewhere in the body