With focused ultrasound (FUS), doctors use ultrasound beams to destroy brain cells that cause movement problems. (It's a bit like using a magnifying glass to focus sunlight rays on a leaf to make a tiny hole.) Using MRI imaging to visualize the brain, doctors guide ultrasound beams to destroy tiny areas of cells that cause Parkinson’s motor symptoms. Doctors target different brain areas for different symptoms.
In 2018, the FDA approved focused ultrasound (FUS) for Parkinson's tremor. In 2021, the treatment gained an expansion of FDA approval to include other Parkinson’s symptoms, such as stiffness or slowness, as well as dyskinesia (uncontrolled, involuntary movement). MJFF funded an early study of focused ultrasound for dyskinesia.
Focused Ultrasound Surgery
During the FUS procedure, a patient is awake. No general anesthesia, surgical incisions or implanted hardware is involved. Doctors use MRI brain scans to direct ultrasound beams to the target brain location. (For tremor, it’s the thalamus and for other Parkinson’s motor symptoms and dyskinesia, it’s the globus pallidus interna.)
Focused ultrasound typically decreases symptoms immediately. It does not require adjustment, programming or additional procedures. But it is irreversible and permanent. Possible side effects may include headache, numbness and tingling, imbalance or gait changes, and others.
FUS is approved only for treatment on only one side of the brain, meaning it only helps symptoms on one side of the body. This is because, when done on both sides of the brain, FUS may cause speech, swallowing or memory problems. (But ongoing research is evaluating the possible benefits and safety of both-sided FUS in different brain targets as well as the best protocols for performing the procedure.)
Focused Ultrasound vs. Deep Brain Stimulation
Focused ultrasound and deep brain stimulation (DBS) are both surgical procedures that aim to ease Parkinson’s movement symptoms or dyskinesia. These therapies may be options for people who get a good response to levodopa but have complications, such as dyskinesia or “off” time. Or, they may be a consideration for people who have tremor that cannot be controlled with medication.
Focused ultrasound and DBS work in the same brain areas but in different ways. FUS destroys cells and DBS delivers small electrical pulses to those same cells to interrupt abnormal signaling. FUS is permanent and irreversible, while DBS may be reversed by removing the system or turning it off. Focused ultrasound is non-invasive — there are no incisions and there is no hardware placed in the body. In DBS surgery, doctors insert thin wires into the brain and a battery below the collarbone. For both FUS and DBS, a patient typically is awake, but some centers now offer asleep DBS. FUS is a one-time procedure that does not require adjustment. DBS needs regular programming to find the right electrical stimulation settings to maximize benefit and limit side effects.
Focused ultrasound may be an option for people who can't or don't want to pursue deep brain stimulation. Some are unable to undergo invasive surgery because of other medical problems. Others may not want to manage the logistics of DBS programming and future battery replacements. Focused ultrasound may expand the available treatment choices for patients and doctors.
Research into Focused Ultrasound
Ongoing research on focused ultrasound for Parkinson’s is evaluating the procedure in different brain areas affected by Parkinson’s, such as the subthalamic nucleus and the pallidothalamic tract. At the same time, scientists are looking at the possible benefits and safety of both-sided FUS in different targets as well as the best practices for performing this procedure. (Observing for six months between each side of the brain, for example.)
Researchers also are studying how ultrasound could help other Parkinson’s treatments, such as antibodies against alpha-synuclein or gene therapies, get into the brain more easily and efficiently by temporarily opening the brain’s protective barrier.