The Pros and Cons of Focused Ultrasound Ablation for Parkinson’s Disease

Focused ultrasound ablation has been in the news recently as an alternative treatment for Parkinson’s disease. It is a technique that uses inaudible, high-energy sound waves to heat and damage a small area of ​​the brain to reduce severely disabling symptoms in Parkinson’s disease. inhibit Parkinson’s. According to neurosurgeon Saman Vinke of Radboudumc, it is still too early for too much optimism: “The technique has yet to prove its value in the total package of treatments.”

Focussed Ultrasound

It is a worldwide hype, especially after the prestigious New England Journal of Medicine recently published a research article about Focussed Ultrasound (FUS) ablation for Parkinson’s disease. A technique in which ultrasonic waves guided by MRI images can be used to very precisely damage brain structures. The researchers report that 45 of the 65 patients responded well to the treatment, in which a lesion (damage) was made in one of the deep brain nuclei (globus pallidus) in one hemisphere. 7 of the 22 patients who received a sham treatment also responded well. One year later, 30 patients in the treatment group were still benefiting from the procedure. Side effects of the treatment included speech, gait and visual disturbances, loss of taste and visual weakness.

Neurosurgeon Saman Vinke is still hesitant about the new technique

Well informed

The question is at what time for which patients with Parkinson’s FUS could be a good treatment. “Since that publication, patients regularly ask whether the treatment is suitable for them,” says Vinke. “Then I say that the place of focused ultrasound in the entire range of treatments for advanced Parkinson’s is not yet clear, that much more research is really needed. That it is not yet close to what we can do with deep brain stimulation – DBS. When it comes to surgical intervention in Parkinson’s disease, DBS is now effectively the standard, and for good reason. As a neurosurgeon, I think it is important for the clinic to represent the options for the patient as accurately as possible, so that we can make the right choice of treatment in consultation with the patient.”

Three brain nuclei

Neurological disorders such as Parkinson’s are not sharply defined; they are disorders in a network of cooperating brain regions. The globus pallidus, the subthalamic nucleus (STN) and the thalamus play a role in Parkinson’s disease. They are therefore the preferred locations for neurosurgical procedures. The relevant FUS article concerns a unilateral damage in the pallidum. “This target can have a good effect on some symptoms of the disease, but does not lead to the possibility of reducing the use of drugs, for example. If you take the thalamus, you only reduce the tremor. But it is the STN that actually has the most influence on all symptoms; on stiffness, slowness, trembling, fluctuations and the tapering off of medicines. In that respect, for many patients with FUS you do not have the optimal location.”

A unilateral operation

Perhaps the most important point: the FUS makes a lesion in only one hemisphere. “You almost always make lesions unilaterally, because the risk of unpleasant side effects is much greater if you do it on both sides,” says Vinke. “The concept of unilateral intervention comes from the past when lesion surgery was still the most common surgical treatment. The symptoms of Parkinson’s usually develop on one side, but after a while all patients actually develop problems on both sides of the body. In the FUS article you see especially good results on the treated side and especially in young patients. In general, these are precisely the patients who are a good candidate for DBS. But what if later problems on the other side also get worse? Then you have actually treated them insufficiently with FUS. We prefer not to apply a lesion on the other side for the time being, so you may still end up with DBS.”

DBS is a dynamic technique

Compared to FUS, DBS has better credentials in this area, says Vinke. “Due to the dynamics of Parkinson’s disease, symptoms are currently more manageable with DBS. Deep brain stimulation does not destroy brain tissue, but works on the basis of electrical pulses. In both hemispheres, for example, we place an electrode with eight contact points in the subthalamic nucleus, which can all be adjusted individually. That is a disadvantage on the one hand, because it takes quite a bit of time to set it up properly. But it has the advantage that we can adjust the electrical pulses again and again according to the patient’s symptoms that get worse over time. In a lesion, you destroy a small piece of brain tissue. That is definitely gone and the effects of it can no longer be adjusted. This applies to both desirable and undesirable effects. Adjustments are possible with DBS. Incidentally, FUS is called non-invasive in the NEJM article, but that is not correct. No hole is made in the skull, but a small piece of brain tissue is permanently damaged. Non-invasive is therefore not a good description of this technique.”

A lot of fuss about FUS?

Of course, such a research article is partly driven by the industry, says Vinke, but that is not necessarily a problem. “For the development of new technology and the production of equipment you always need companies. But the question is always whether what is offered really has added value for patients. Especially if it threatens to become a hype. As a practical matter: in addition to an MRI, you also need new equipment for this procedure. As a professional group, should we immediately go along with this and install such machines in every centre? I think that in a limited number of research institutions, the effects of the treatment and which patients will benefit from it should first be carefully examined. As DBS operations are becoming increasingly safe, the group of PwPs who are physically unable to handle surgery, and therefore may benefit from FUS, seems to be getting smaller. But it is certainly an interesting technique and maybe in about five years we will be able to burn a hole in both hemispheres without many side effects. It may be an interesting treatment for a subgroup of patients. Then you could gain a lot without surgery and foreign material in the brain – the electrodes. But at the moment, compared to DBS, it is too early to introduce FUS as an equivalent treatment for PwPs.”

Focussed Ultrasound must first prove itself even better

In the accompanying commentary in the New England Journal of Medicine, Anette Schrag of University College London comes to a similar conclusion. FUS is a promising technique, which is also potentially safer than ablation with radiofrequency ablation (RF), which does open the skull minimally. The research is promising, she writes, “but given the irreversible nature of the procedure and the progressive development of the disease, it is important to determine whether the improvements in motor complications persist over time and whether the treatment results in better overall functioning and a better quality of life for the patients”. For the time being, Vinke sees the FUS more as a research technique than as a full-fledged therapy.