Q&A: Weill Cornell Medicine physician talks HIFU technology, treating essential tremor

High-intensity focused ultrasound (HIFU) is a technology that has been used to address benign tumors in the uterus and cancerous prostate tumors. But it’s now being used to treat essential tremors after the FDA approved it in July.

Michael Kaplitt, MD, PhD, vice chairman for neurosurgery research at Weill Cornell Medicine, was the first physician in New York to perform a HIFU procedure, which eliminates shaking in the hands, head and body.

Previously physicians have treated tremors through an invasive brain surgery that sometimes results in damaged tissue. Medications are also prescribed to treat tremors, including those that reduce adrenaline or subdue the brain. But the side effects often make patients groggy and unable to go about their daily lives.

By using the ultrasound technology, doctors can non-invasively target the part of the brain causing tremors and test patients’ motor skills throughout the procedure until they find the precise spot that will stop them for good.

So far, Kaplitt has performed the procedure on two patients and has more scheduled in the near future.

He first performed the procedure at the end of August on Alexandra Lebenthal, 52, a high-profile businesswoman on Wall Street. After suffering with essential tremor for most of her life, she now can write more clearly and has an easier time accomplishing everyday tasks like drinking and eating.

In an interview with Radiology Business, Kaplitt discusses HIFU, how it works and the most difficult part of doing it right.

Radiology Business: What causes essential tremor?

Michael Kaplitt: Nobody is really sure. We do know that it can run in families, so a lot of patients with essential tremor have close relatives—parents, uncles, siblings—who also have the disorder. It’s a movement disorder, but unlike other movement disorders, such as Parkinson’s disease, essential tremor is really an isolated symptom. It’s what's called an action tremor or an intention tremor, meaning it’s a tremor when you try to move.

Can essential tremor eventually lead to other, more serious conditions?

It doesn’t usually lead to more serious conditions, but over time, the tremor worsens. For most people, it can get to the point where it’s difficult to do normal activities without severely shaking, such as picking up a cup and drinking, eating with your hands and writing.

How does HIFU technology work exactly?

Focused ultrasound is based on a long-standing concept that if you can interrupt abnormal signals coming from an area of the brain in the middle of a circuit that regulates stability of movement, then you can improve the disease. While we do not know what the underlying cause of the disease is, we do know that this particular circuitry in the brain is influencing the tremor. If we can go into that circuitry and interrupt the abnormal signals that are flowing through that circuit to the rest of the brain, we can improve the tremor.

MR-guided focused ultrasound essentially tries to take advantage of what we know about this circuitry, but alter the function of this circuitry in a completely non-invasive way. The idea is that ultrasound energy can go through the skull and through the brain. Most people are surprised to hear that, but it can. The problem is that if you just take a single source of ultrasound and put it through, it can scatter and it doesn’t really deliver enough energy to whatever target you’re interested in to do anything.

Walk me through the procedure.

You put a stereotactic frame on the patient’s head, a box that just holds their head in place. It’s external. There’s nothing inside their head. There are no incisions. This fixes their head in place so that they can’t move and it helps us with targeting. We put the patient’s head into this device and then the helmet fills with cool water because ultrasound needs to go through water. The ultrasound beams will go through the water, through the scalp and through the skull into the brain. We then use the MRI to measure the temperature at the spot using a technique called MR thermometry, which means that we can actually measure the temperature in a given area of brain tissue, non-invasively using the MRI because ultimately what the MRI does when it creates a picture of the brain, is it’s creating a picture based on energy that’s being released from different molecules in the brain. It’s therefore interpreting what those molecules are in making a picture, and we can measure the temperature at the source or at the spot.

What temperature are you looking for?

Initially, we will heat the target spot to a low level temperature. In Celsius, our body temperature is roughly 37 degrees. We’ll heat it up to be between 42 and 45 degrees Celsius, which is not enough to cause any type of permanent change, but gives us an initial look at whether the spot that we’ve chosen is giving the patient any benefit or is causing any side effects, such as difficulty moving, speaking or numbness or tingling in the hands. If the patient is not having any side effects at that temperature, and they start to see some element of improvement at a low grade, say 30 percent, then we know we’re in the right spot. We then raise the temperature at that spot until we get to a temperature of around 55 or 60 degrees Celsius that will make this change permanent. That will permanently destroy that small spot of brain tissue, which is causing the problem.

How do you determine where the right spot is in the brain?

It’s a very small spot. It’s usually roughly 3 millimeters in diameter. If, at a low temperature, the patient is not having much benefit but they’re having some side effects, then we move the target a few millimeters away from the initial target in whatever direction we think is the best until we eventually get it to the point that at that low temperature they’re having a small amount of benefit without side effects. That’s when we make it permanent. We wait until we see the right combination of benefit and absence of adverse effects and then we make it permanent, which provides a measure of safety for the patient.

How do you know when the tremor is gone?

Every time we change the temperature, we’re bringing the patient out. We roll them out of the MRI and test how they’re doing. We objectively test whether they can write better—whether they can draw a circle or write their name.

Are patients immediately cured of the tremor after you’ve targeted the right spot?

Once you do that, the patient’s tremor gets better immediately, right there on the MRI table. When they’re done, we take the box off and they’ve got no incision in their head, they’ve got no hole in their skull, they’ve got no device in their body.

How does the procedure vary from patient to patient?

For each patient, we’re always targeting the same structure, the VIM nucleus of the thalamus. We’re always targeting that area of the brain. What differs from patient to patient is exactly where that ideal spot is relative to the rest of their brain. It’s always in the same general vicinity, but the exact, precise target can vary a couple of millimeters in any given direction from patient to patient depending on what else is going on with their brain and their anatomy.

Is that the most difficult part of completing the procedure?

It’s not excessively difficult because it’s based on techniques and methods that we’ve used for a long time. It’s just that the device itself has a lot of little steps. Then there is this trial-and-error aspect to it where you have to get a sense of whether you’re in the right spot or not. You need to be able to have a picture in your head of what that patient’s brain really looks like. When you’re doing your initial heating and you get the feedback from the patient, you have to visualize in your head where you think that is. Is that in the ideal spot? And if it’s not, you have to know what direction it’s off so you know which way to move.

Is there any recovery time for the patient?

For the study we’ve been doing, we’ve been keeping the patients overnight. But the patients have all done so well that in the future, it’s entirely possible that we’ll send patients home the same day once we get comfortable enough.

Why was Lebenthal a good candidate for this procedure?

She’s a very accomplished, high-profile person, and yet the tremor was always a problem for her and it was getting worse. She was unable to write her name. She was unable to drink reasonably with one hand. It was tough for her to eat, so she had many quality of life problems because of the severity of this tremor and she was otherwise pretty healthy.

She did not like the idea of having a device permanently in her body, and she could not tolerate many of the medications beyond a very low dose. She had side effects from them, so she really did not have much of a medical option. The choice was either live with this or try to do something about it. 

This interview was edited for clarity and space.