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Essential Tremor Treatment Advancements Using MRI-guided Focused Ultrasound: Q&A With Jeffrey S. Schweitzer, MD, PhD

In This Article

  • Essential tremor arises from abnormal oscillations within the cerebello-thalamo-cortical circuit
  • MRI-guided focused ultrasound (MRgFUS) targets the thalamus's ventral intermediate nucleus, using precise beams of sound energy to suppress tremors without invasive surgery permanently
  • Candidates for MRgFUS include those whose quality of life is significantly affected by essential tremors or Parkinson's tremors and who have not found adequate control through other treatments
  • MRgFUS represents a significant advancement in tremor treatment, offering a non-invasive, precise, and safer alternative to traditional surgical interventions

Jeffrey S. Schweitzer, MD, PhD, a neurosurgeon in the Department of Neurosurgery at Massachusetts Hospital, specializes in treating epilepsy, essential tremor (ET), and tremor-dominant Parkinson's diseases. In this Q&A, Dr. Schweitzer discusses the physiological processes underlying essential tremor and the advancements in noninvasive therapy, MRI-guided focused ultrasound (MRgFUS). He explains the criteria for selecting MRgFUS candidates for this cutting-edge intervention: a non-invasive, precise, and safer approach compared to traditional surgical procedures.

Q: What are the physiological processes that lead to essential tremor?

Dr. Schweitzer: The exact cause of this common movement disorder is not well understood, and multiple mechanisms may be responsible. In general, it can be seen as the result of abnormal oscillations within a circuit in the cerebello-thalamo-cortical circuit, which controls bodily position in space. The ventral intermediate nucleus (VIM) of the thalamus, which receives cerebellar input and projects to the motor cortex, is a critical node in this circuit. Overactive feedback activity in this network is thought to lead to oscillation around the desired position, resulting in the tremor seen in ET.

Q: Can you elaborate on how MRI-guided focused ultrasound targets the brain regions responsible for essential tremors without harming surrounding tissues?

Dr. Schweitzer: For the reasons previously described, the target for MRgFUS is the VIM nucleus. This can be located using the MRI scanner's direct and indirect imaging methods. With a patient in the special MRI scanner and the ultrasound-generating helmet attached, hundreds of precise beams of sound energy are focused on this target. The sound energy level is gradually increased one step at a time, which raises the temperature of the tissue at the focal point, and the patient is examined for tremors after each step. The special MRI shows the temperature of the tissue. The location and energy levels are carefully adjusted until the tremor is suppressed with no side effects, and then the energy level is raised high enough to make the treatment's effects permanent.

Q: What are the criteria for selecting patients for MRgFUS treatment, and when is someone an ideal candidate?

Dr. Schweitzer: People may be candidates for MRgFUS for tremor if their ET or Parkinson's tremor significantly affects their quality of life and if more conservative means, including physical methods like weighted gloves for ET or medications for either ET or Parkinson's disease, do not adequately control the problem. This decision is made after careful consideration and discussion between the patient, neurologist, and neurosurgeon, usually requiring a thorough examination and evaluation by a team of movement disorder specialists. Alternative treatments, such as deep brain stimulation (DBS), may also be considered. Although MRgFUS is non-invasive in the sense that no incisions are made, it is still a form of surgery, and as with any surgery, it is important for prospective patients to understand the risks and benefits and to have all their questions answered before making a decision.

Q: Could you describe the improvements in symptoms patients often experience following the MRgFUS procedure?

Dr. Schweitzer: Most patients will experience immediate and often dramatic improvement in their tremors immediately after the procedure. The benefit is intended to be permanent and long-lasting in most people, but in some patients, there can be some return of the tremor over time. Tremor is often a gradually progressive symptom, and the treatment must be conservative enough to avoid side effects.

Q: How does the recovery process from MRgFUS compare with that of traditional surgical interventions?

Dr. Schweitzer: Surgical treatment that creates a temperature-based lesion in the VIM nucleus to control tremors has a long history. It was the main surgical treatment before DBS was developed 25 years ago, but it was done with open surgery and an electrode placed into the target in the brain. The temperature at the tip of that electrode was estimated. MRgFUS differs from those previous methods in that it requires no incision, no devices are placed into the brain, and it gives precise information about the target and temperature. Unlike DBS, it does not require multiple visits for pacemaker programming, and there is no need for general anesthesia or surgical incisions. MRgFUS, because it uses sound waves to produce heat, does cause more swelling around the target than does DBS, so MRgFUS patients are more likely to experience side effects like mild imbalance, incoordination, or tingling in the fingers in the few days following treatment. These side effects fade away over time. Also, with MRgFUS, only one side of the brain is treated at a time. The other side can be treated after nine months if the patient wishes.

Q: Are there any risks or potential side effects associated with MRgFUS that patients should know?

Dr. Schweitzer: Yes, as discussed above, there can be mild difficulty with balance and coordination in the days following treatment that fades over time. Occasionally, some of these side effects can last longer. This is one reason it is important to have a full and detailed evaluation by the movement disorder specialty team before deciding on MRgFUS therapy; patients who already have underlying issues like balance disorders or peripheral neuropathy might wish to consider other treatment methods. It is also the reason for the nine-month interval if both sides are to be treated.

Q: What makes MRgFUS a significant advancement over other treatments for essential tremors and tremor-dominant Parkinson's disease?

Dr. Schweitzer: MRgFUS is a high-tech, safer, and more precise implementation of a well-understood traditional surgical treatment. For people who are not candidates for DBS because of medical conditions that make such surgery too high risk, who would have difficulty with the requirements for programming and battery changes required with DBS pacemakers, or who cannot have or do not want invasive surgery and permanently implanted wires and pacemakers, MRgFUS may be an excellent option to overcome the disrupted quality of life caused by ET of PD tremor.

Learn more about essential tremor treatment

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