The director of functional neurosurgery at Baptist Health Miami Neuroscience Institute provided perspective on the growth of high intensity focused ultrasound and the lessons learned when treating essential tremor.
Essential tremor is a nervous system disorder that causes involuntary and rhythmic shaking. It typically begins gradually, usually more prominently on one side of the body, and worsens with movement. The timing of tremors, associated conditions, and areas of the body affected, can all be key indicators on the differences between essential tremor and Parkinson disease. To date, the 2 biggest known risk factors for essential tremor include age, as the condition is more common in people aged 40 and older, and an altered gene, increasing the potential for developing the disorder.
Over the years, the treatment landscape has changed significantly for essential tremor. In terms of medications, there are beta blockers, antiseizure medications, tranquilizers, and onabotulinumtoxinA, as options to treat symptoms of essential tremor. If tremors are severely disabling and patients aren’t responding to medications, surgical options like high intensity focused ultrasound (HIFU) have become a reliable go-to option for clinicians. This minimally invasive procedure uses ultrasound waves that interact with targeted tissues in the body to modify or destroy them. Outside of essential tremor, HiFU has been used for other conditions like tumors and uterine fibroids.
Neurosurgeons at Baptist Health, including Justin Sporrer, MD, have been at the forefront of using HIFU to treat essential tremor. The institution is approaching 100 patients treated with HIFU, a landmark for the community. As part of a new iteration of NeuroVoices, Sporrer, director of functional neurosurgery at Baptist Health, sat down to discuss the advances made in this approach and why it continues to be such an effective treatment. Additionally, he spoke on the lessons learned from the growing number of HIFU-treated patients, and ways to expand this approach in the future.
Justin Sporrer, MD: High intensity focused ultrasound or HIFU is a very good treatment for tremor to this point. We have had treatments in the past, such as pharmacologic medications, as well as something called deep brain stimulation; however, the medications have been fairly ineffective, in my opinion, or if they are effective, it's for a short amount of time and then they become ineffective. Deep brain stimulation is also extremely effective and can be quite useful, but there is a population of people who are not candidates for that because of their age or because of medical problems that would prevent traditional open brain surgery. Even though it's low risk, there is another population of people who do not want to have brain surgery in the traditional sense. For either of those two groups of people who have tremor, the high intensity focused ultrasound has been a great tool added to our belt.
This is a 2-part answer. Firstly, we've known for decades that an ablation or damage to a very specific population of cells within the thalamus results in tremor suppression. The difference is that in the past, we had to do that surgically by inserting a thermal electrode and heating up the tip, burning those cells and then suppressing tremor. But of course, you didn't get to avoid traditional surgery, it still required an incision, with all of the inherent risks, such as bleeding and infection. Along comes high intensity focused ultrasound, which achieved the same result, but with no incisions and no surgery, or the risks associated with it. The research began probably more than 10 years ago, and it was first used about a decade ago. Once FDA approval was achieved, it continued to grow from there. Another hurdle was approval from Medicare to pay for it, which went state by state. Florida was one of the last states to approve it, which happened approximately 3 years ago. That’s sort of the evolution we’ve had. Recently, 2 months ago, the FDA approved performing high intensity focused ultrasound thalamotomy for the second side of tremor, which was not previously indicated for.
For patient number 1 here at Baptist, we wanted to make sure that we knew exactly what we were doing with all the appropriate training. And then, for myself, being convinced that the literature supported this treatment. Patient number 1 was getting the correct treatment and everything was great. But of course, you learn as you go in terms of the little nuances. First would be efficiency. I think our first patient took something like 3 hours on the table, which in some ways doesn't sound so bad. But when you're laying flat on your back, it can be a little bit daunting, and we've gotten that number down to about one hour. The procedure is done inside of an MRI machine, which can cause some claustrophobia in some patients, but you're only in the machine for only a portion of that hour with lots of breaks in between. From that perspective, we've gotten a lot more efficient. Then, its the little things like having a single patient have nausea and learning from that so that we can give everybody anti-nausea medicine in preparation for that. Those kinds of things help us to make it a more pleasant experience a more effective experience and more efficient.
This is just my opinion, but I think the idea behind it is to disrupt an abnormal circuit. It just happens to be that we have a pretty good understanding of the circuit that controls movements, particularly the movements that are affected by tremor. We know where to target these abnormal cells to disrupt that circuit and achieve tremor suppression. But of course, everything that you do and say and think is the result of abnormal circuit or a normal circuit if it's working properly. If we can have a better understanding in the future of the various circuits, for example, in various psychiatric illnesses and other movement disorders, and have an effect there, then I think there is potential for this technology and other technologies to reestablish the correct circuitry, the correct communication between these various neurons.
Transcript edited for clarity. Click here for more iterations of NeuroVoices.