Focused ultrasound for Parkinson’s: ask the expert

Most people with Parkinson’s will use medication to help control their symptoms, but for some, over time, medications alone may no longer be enough to control symptoms. This is when specialists may look towards surgical options. Currently deep brain stimulation (DBS) offers the main surgical way to control movement symptoms of Parkinson’s.

This type of surgery involves inserting fine wires into the brain to be controlled by a pulse generator (a device like a heart pacemaker) that is placed under the skin around the chest or stomach area. When the pulse generator is switched on, the electrodes deliver high frequency stimulation to the targeted area. This stimulation changes the electrical signals in the brain that are causing some of the movement symptoms of Parkinson’s.

Read more about the brief history of surgery for Parkinson’s in a previous blog post.

But what if there was another way to target cells deep within the brain? This is where a technique called focused ultrasound comes in. It offers a way to change the way the brain works without the need for invasive brain surgery.

In this blog, we find out exactly what focused ultrasound is and how it might help people with Parkinson’s in the future.

To learn more, we spoke to Professor Wladyslaw Gedroyc, Consultant Radiologist at Imperial College Hospital, who has over 20 years of experience investigating the potential of focused ultrasound.

What is focused ultrasound?

Ultrasound is a technique many people are already familiar with. For instance, ultrasound can be used to safely see a baby growing inside an expectant mother’s belly or to look at the heart and surrounding blood vessels in a procedure known as an echocardiogram. This technique uses a probe that releases sound waves, these bounce off objects in their path and are reflected back to the probe to help build a picture.

But when we are talking about brain focused ultrasound technology, this uses a much higher power but lower frequency of sound waves, about 40 thousand times the power of that normally used in diagnostic ultrasound. This is because the high power sound waves are not being used to see inside of the brain but to target problematic or misbehaving cells, heating them until they are destroyed. At this power the sound waves heat tissue to over 55 degrees Celsius, destroying key cellular proteins and leading to cell destruction.

This technology is particularly exciting with regard to targeting cells in the brain, and this can be achieved using a transducer that produces high power sound waves, arranged in a helmet like configuration. The high powered nature of the sound waves allows them to pass through the skull to target and destroy brain cells at a specific site that is involved in movement problems, usually tremor. This essentially gives us a way to apply destructive energy deep within the body in a controlled manner. You can think of this like a magnifying glass that can focus the sun’s energy to burn a hole in a leaf.

How do you target and control this technology?

We use magnetic resonance imaging (MRI) to visualise the brain in real time, and to see the precise location that the ultrasound waves are reaching and how much heat they are producing. This is why you may have heard people refer to this technique as MRI-guided focused ultrasound, since MR can provide an image of the heating process and measure the temperature being produced in the deep brain tissues.

We use this guiding technique initially with lower power ultrasound, which isn’t going to permanently destroy cells, to see how the patient responds to targeting a specific location within the brain. At this stage the tissue effects are reversible, so we talk with and examine the patient to ensure that there are no evident side effects before turning up the power to permanently destroy cells in a carefully targeted way, if the target is suitable.

What is focused ultrasound currently used for?

A lot of work has been done using this technology to treat people with essential tremor. This is a debilitating condition where people have an uncontrollable tremor when they are actively carrying out tasks. This is often distinct to the tremor experienced in Parkinson’s, as people with this condition tend to experience what’s known as a resting tremor, which is when people experience a tremor when they are not actively engaging in an activity.

Within the UK about 30 people with essential tremor have received focused ultrasound treatment, and we have seen on average an 80% improvement in people’s tremor after 2 years. There have been similar results observed in other countries. We currently don’t know about the long term nature of these improvements beyond 2 years, but we will continue to monitor these patients.

Despite the encouraging results we can currently only offer the procedure privately or as part of research studies. It is hoped that by the end of the year, the treatment will be approved for use on the NHS for people with essential tremor. This will depend on NHS England agreeing to fund this form of therapy.

Why is this relevant to people with Parkinson’s?

As I said, so far most of the work has been done in people with essential tremor but these techniques are now being applied to Parkinson’s.

Parkinson’s can affect people in different ways. Those people that have what is known as tremor dominant Parkinson’s, can be treated in a similar way to those undergoing focused ultrasound treatment for essential tremor by interrupting the tissue pathways that contribute to the cause of tremor in the nucleus ventralis intermedius (VIM).

We have treated a few patients with tremor dominant Parkinson’s, currently about 5, and we see similar improvements to those with essential tremor. But there have been much fewer research studies investigating focused ultrasound for Parkinson’s so more research is needed before this technique can be recommended and available on the NHS for people with Parkinson’s.

We want to carry out a randomised clinical trial to see if focused ultrasound is beneficial to people with tremor dominant Parkinson’s. This is something that is currently under discussion.

There is also ongoing research looking at focused ultrasound for people with other types of Parkinson’s, for instance, bradykinetic Parkinson’s. Bradykinesia means slowness of movement and can be responsible for symptoms such as freezing. The results from this trial can hopefully be expected soon.

Another exciting piece of research is happening in Madrid and being carried out by Professor Obeso. The methods I have mentioned so far are targeting an area of the brain called the nucleus ventralis intermedius to help control tremor. This new trial aims to use focused ultrasound to target cells within a different part of the brain called the subthalamic nucleus, and some would say this is the best place to treat Parkinson’s both for tremor and bradykinesia. Nonetheless, targeting this region of the brain is much riskier. We eagerly await the results of this study.

Read more about the trial in Madrid on the Focused Ultrasound Foundation website.

Once we have a better understanding of which regions of the brain should offer the best targets in Parkinson’s, this technology could have scope for treating more than just tremor.

How does this technique compare to DBS?

DBS works in a different way to focused ultrasound, DBS overwhelms the faulty circuits whereas focused ultrasound destroys the circuits, to help with movement symptoms.

The advantage of DBS is once the electrodes are in the correct position in the brain you can turn it on and off, dial it up and down depending on the severity of the symptoms. Whereas, focused ultrasound is a permanent non-invasive procedure.

One of the current limitations of focused ultrasound is that it is currently only carried out on one side of the brain, since studies using treatment on both sides are only in their infancy at the moment. For most people with Parkinson’s their movement symptoms impact both sides of their body. For this reason, DBS still offers an excellent way to manage Parkinson’s as it can control tremor on both sides.

We are starting to look at using focused ultrasound bilaterally, on both sides of the brain. But we need to be cautious, as in the past a technique called lesioning that targeted regions of the brain on both sides resulted in a high number of people developing speech problems. That being said, this previous technique was much less accurate than focused ultrasound and early results treating both sides are very promising.

There are some huge advantages of focused ultrasound. It doesn’t involve drilling holes in someone’s head which comes with an infection risk, it is also much cheaper than DBS, doesn’t involve overnight stays at the hospital, and has less follow up after the procedure.

Is Imperial the only centre in the UK looking at focused ultrasound and Parkinson’s?

At the moment we are the only centre but other places in the UK are very interested in exploring this technology.

What other exciting opportunities does this technology offer?

There is ongoing research investigating whether this technology can reversibly open up the blood brain barrier to particular areas of the brain. This is extremely exciting because the blood brain barrier currently acts as an extra hurdle for drugs to reach the needed areas of the brain in neurological conditions, and therefore this could hold the opportunity to deliver more efficient and targeted treatment options in the future.

The technology is also being investigated for people with other neurological conditions such as obsessive compulsive disorders and epilepsy.

Huge thanks to Professor Wladyslaw Gedroyc, Consultant Radiologist at Imperial College Healthcare NHS Trust, London.

This blog is not meant as health advice. You should always consult a qualified health professional or specialist before making any changes to treatment or lifestyle.