How can focused ultrasound help PD symptoms?

Focused Ultrasound for Parkinson’s disease

Two brain procedures that are approved for use in PD are deep brain stimulation (DBS) and high-intensity focused ultrasound (FUS). I encourage you to read more about DBS and view our webinar which outlines the newest features of this procedure.

What is high-intensity focused ultrasound (FUS)?

The newer of these two treatments for PD is FUS in which beams of ultrasound waves are focused on a designated target in the body, thereby concentrating enough energy to create a small lesion. Individual ultrasound waves do not contain enough energy to do damage as they pass through the body’s tissue. It is not until multiple waves are all focused on a particular spot that a lesion is formed, which can be therapeutic in certain clinical situations. Previously FUS had been approved by the Food and Drug Administration (FDA) to treat bone metastases, uterine fibroids, enlarged prostate cancer, and essential tremor.

FUS Approved by FDA for Treatment of Parkinson’s Tremor

In 2018, tremor-predominant PD was added as an FDA-approved indication for the use of FUS. In 2021, the indications for the procedure were expanded to include bradykinesia (slowness), rigidity (stiffness), and dyskinesias. When an FUS-induced lesion is created in specific locations in the brain, it can disrupt abnormal PD circuitry. In this procedure, MRI is used to precisely direct the ultrasound waves to deep structures of the brain. The ventral intermediate (VIM) nucleus of the thalamus, a structure that acts as a relay station for many of the brain’s functions, is targeted for tremor. The globus pallidus interna (GPI) is targeted for a more comprehensive treatment of PD symptoms including slowness, stiffness, and tremor. Abnormalities of the circuitry are known to play a role in PD symptoms.

It is interesting to note, that prior to the advent of DBS as a surgical option for PD, lesioning surgery of the thalamus and other brain areas was used to treat the symptoms of PD. In these surgeries, the skull was opened in order to enter the brain and brain tissue had to be disturbed in order to access the deep structures of the brain. FUS can perform approximately the same role as lesioning surgery in a much less invasive way.

DBS vs. FUS

With the additional option of FUS to treat a wider array of PD symptoms, many are wondering which treatment, FUS or DBS, is better to pursue? This requires an in-depth discussion with your neurosurgeon, but I will give an overview of the pros of each procedure.

Pros of focused ultrasound

  • FUS does not require any incisions or holes in the skull. No hardware is left in the body. DBS does require both an incision and a hole in the skull and hardware is permanently placed in the brain and body. This makes DBS more invasive, with an increased risk of bleeding and infection as compared to FUS.
  • In FUS, the individual ultrasound waves that penetrate the brain are too weak to cause damage until the waves converge on the designated deep brain structure. DBS on the other hand requires an electrode to be passed through the healthy brain on its route to the deep brain structures. Although any damage to healthy brain that DBS may cause is minimal, this is even less of an issue with FUS.
  • FUS is a single procedure. DBS requires one procedure to place the electrode in the brain and another to implant the implantable pulse generator (IPG). There are also subsequent visits to program the IPG and adjust settings. The battery also needs periodic replacement.

Pros of deep brain stimulation

  • DBS is done routinely on both sides of the brain. FUS is currently done on only one side as the full side effects of having FUS done on both sides of the brain is not yet fully understood. This may change in the future as more is understood about FUS.
  • DBS has been an FDA-approved procedure for decades. Because of this, neurosurgeons will have much more experience with it than with FUS.
  • Although symptoms of PD progress with time and may therefore lead to an overall worsening of a person’s condition, the effects of DBS itself do not wane. The longevity of improvements from FUS is not yet fully known.
  • DBS is programmable. As PD symptoms progress and change, adjustments can be made to improve the efficacy of DBS. FUS is a procedure that is performed once and can’t be adjusted.
  • The DBS hardware is removable if necessary, which makes the procedure reversible. FUS is not reversible. Once the lesion is created, it is permanently in the brain.

Low-intensity focused ultrasound to help deliver therapies

While high-intensity FUS is a treatment for PD as described above, low-intensity FUS can be used in an entirely different way to help treat PD. This type of FUS may allow for disruption of the blood-brain barrier. The blood-brain barrier refers to the cells that line the blood vessels within the brain which keep foreign substances, such as toxins and microbes, in the bloodstream and out of the brain.

Normally, this mechanism is advantageous and protects the brain. However, the blood-brain barrier may also keep out molecules that could help to treat brain diseases. Therefore, disrupting the blood-brain barrier could allow for penetration of these molecules into particular areas of the brain. A whole variety of different molecules such as antibodies, nerve growth factors, and gene therapy may be able to take advantage of this approach. Further research is necessary to determine if this will be a useful method for drug delivery into the brain.

Tips and takeaways

  • Deep brain stimulation and focused ultrasound are two brain procedures that may be used to help PD symptoms in certain patients.
  • Pros and cons of deep brain stimulation and focused ultrasound are complicated and must be reviewed with the treating neurosurgeon.
  • Focused ultrasound may also one day be used to enhance drug delivery into the brain.
  • Not all procedures make sense for every person with PD, so it is important to talk to your doctor about your options and carefully discuss the risks and benefits of any new treatment or procedure.

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Dr. Rebecca Gilbert

APDA Vice President and Chief Scientific Officer

Dr. Gilbert received her MD degree at Weill Medical College of Cornell University in New York and her PhD in Cell Biology and Genetics at the Weill Graduate School of Medical Sciences. She then pursued Neurology Residency training as well as Movement Disorders Fellowship training at Columbia Presbyterian Medical Center. Prior to coming to APDA, she was an Associate Professor of Neurology at NYU Langone Medical Center. In this role, she saw movement disorder patients, initiated and directed the NYU Movement Disorders Fellowship, participated in clinical trials and other research initiatives for PD and lectured widely on the disease.

A Closer Look ArticlePosted in Parkinson's Treatments

DISCLAIMER: Any medical information disseminated via this blog is solely for the purpose of providing information to the audience, and is not intended as medical advice. Our healthcare professionals cannot recommend treatment or make diagnoses, but can respond to general questions. We encourage you to direct any specific questions to your personal healthcare providers.