MRI-guided Focused Ultrasound (MRgFUS) was approved by the FDA in July 2016 for the treatment of essential tremor (ET) that does not respond to medication. Since about half of those with ET find that medication either doesn’t work, or stops working after a period of time, or they don’t like the side effects, the idea of an outpatient, one-time treatment to control hand tremors can sound like a dream come true—but as with any dream, questions arise. Here are 5 questions we hear most frequently.
1. How does MRgFUS stop tremors?
MRgFUS is an incisionless, noninvasive brain surgery that uses image guidance to focus waves of ultrasound on a target within the brain. The target is a tiny part of the thalamus, a center that relays sensory information to other brain areas that then act upon it. The tiny part that forwards malfunctioning tremor signals to the hands is called the VIM nucleus. When the ultrasound waves intersect at the VIM nucleus, they create a high temperature that destroys the VIM nucleus. Although the tissue destruction is permanent, the precision of the treatment means that no other damage is done anywhere else in the brain, so no other movement functions are disrupted.
2. Does this stop tremors in both hands?
No. The thalamus has a left half and a right half. As with the entire brain, each half controls the opposite side of the body; the left VIM nucleus controls the right hand, and vice versa. During MRgFUS, only the side that controls a person’s dominant hand is treated. Early clinical studies showed that treating both sides at once had a greater risk of side effects. Some research is currently being done to explore the option of treating the opposite side many months after the first treatment, but the safety profile of this lacks long term data.
3. Is image guidance enough to make sure you’re hitting the right place?
There are actually two ways to ensure we’re treating the correct area. Today’s Magnetic Resonance Imaging (MRI) done on a powerful 3 Tesla (3T) magnet has incredible 3-dimensional resolution. It reveals the target area—in this case, the VIM nucleus—with great accuracy. This means the neurosurgeon literally “sees” the brain’s anatomy in real time and can plan the treatment accordingly. In addition, once the target is identified, we start with gentle “test shots” of Focused Ultrasound to evaluate how the tumor is being affected. The patient is also able to report any unusual sensations, such as a tingling sensation in the face. During this phase, adjustments are easily made in order to assure success while avoiding unwanted side effects.
4. Does this mean the patient is awake during treatment?
Yes, we need the patient to be conscious in order to communicate what he/she is experiencing, and also to follow instructions. For instance, once the full strength of the treatment begins, we can measure its effectiveness by asking the patient to do things like sign his/her name or draw a spiral. As the tremor gradually disappears, both the doctor and the patient can see the results. When tremor is controlled to everyone’s satisfaction, the treatment is complete. The patient can get dressed and go home.
5. Is the tremor gone forever?
To be honest, we really don’t know. As noted in the beginning, the FDA approved the treatment in mid-2017. This approval was granted based on only a few years of clinical trials—which, by the way, were so effective that the full trial was ended early so that those in the control (non-MRgFUS) arm of the study were able to receive the treatment. In other words, this treatment has not been around long enough to know if its effect is permanent. What we do know is that for those who have been treated so far at Sperling Neurosurgery Associates, none has yet had recurrence in the treated hand. More study needs to be conducted to find out if it would be safe to go back and expand the treated area slightly, and if it will ultimately be safe to treat the opposite side for patients who so desire.
An optimistic future
The future appears rosy for MRgFUS as a tremor treatment. Already, patients with Parkinson’s disease (PD) whose tremors are uncontrollable with medication are being enrolled in a clinical trial, though a slightly different brain region is the target in PD since those tremors are due to a different brain disorder.
MRgFUS is more than just a promising treatment. For the more than 1000 people whose ET has been successfully managed by MRgFUS, it may rightly be called a transformation.