Advanced treatments for essential tremor: identifying candidates

Deep brain stimulation (DBS) and MRI-guided focused ultrasound are advanced treatments for essential tremor, but which patients are suitable candidates? In this lesson, you’ll compare how the procedures work, their expected benefits, and their limitations. Learn the patient selection criteria to assess whether advanced therapy is an appropriate next step for your patient. Then put your knowledge to the test with three patient profiles.

In this lesson from our Tremors Masterclass course, you'll learn how to:

• Explain how deep brain stimulation (DBS) and MRI-guided focused ultrasound treat essential tremor
• Describe the benefits and limitations of each procedure
• Assess candidacy using patient selection criteria
• Compare unilateral and bilateral treatment approaches
• Recognize how cognitive impairment affects candidacy
• Apply the selection criteria using three patient examples

Advanced treatments for essential tremor

[0:00]
Advanced therapies for [essential tremor] ET include deep brain stimulation, or DBS for short, and a lesioning therapy called MRI-guided focused ultrasound. Both therapies target the ventral intermediate, or VIM, nucleus of the thalamus.

How deep brain stimulation (DBS) suppresses tremor

[0:17]
DBS is a surgical procedure where an electrode is placed within a target brain structure. It's attached to a wire that runs underneath the skin and is connected to an implantable pulse generator, or IPG, overlying the chest. The tips of the electrodes, called the DBS leads, have four levels of metal contacts. When the IPG is turned on, electrical signals from the IPG travel through a contact in the lead and stimulate the surrounding tissue, suppressing the tremor. Once stimulation is optimized, there may be a 60 to 90% improvement in tremor.

How MRI-guided focused ultrasound treats tremor

[0:56]
On the other hand, MRI-guided focused ultrasound creates a lesion using a helmet that focuses ultrasound beams through the skull. The beams converge on the thalamus, and heat produced by the beams destroys the tissue. Tremor improvement with focused ultrasound is typically between 40 to 60%, slightly less compared to DBS.

DBS vs. focused ultrasound for essential tremor

[1:20]
There are pros and cons to each procedure. DBS doesn't destroy brain tissue, whereas focused ultrasound produces a permanent lesion that can't be reversed. However, DBS is brain surgery, with incisions, drilling of the skull, and hardware implantation, whereas focused ultrasound doesn't require incisions.

Advanced treatments for essential tremor: identifying candidates

[1:41]
So which patients are candidates for these therapies? Well, the ideal candidate has an upper extremity action tremor that interferes with their quality of life. Candidates should also have tried adequate trials of at least 240 milligrams a day of propranolol and 250 milligrams a day of primidone, as long as they don't have side effects.

Unilateral and bilateral treatment for upper extremity tremor

[2:04]
These advanced therapies are most effective for upper extremity tremors in ET, with more variable results for head or voice tremors. For DBS, leads can be placed bilaterally to help the tremor in both hands, though many patients can get by with unilateral DBS to control the tremor in just their dominant hand. Some centers will place bilateral DBS leads at the same time, while other centers will do a staged implantation, where the second lead is implanted several months after the first. For MRI focused ultrasound, staged procedures are performed if bilateral treatment is needed, with the second side lesioned nine months after the first side.

Cognitive impairment and advanced tremor therapies

[2:49]
Patients with dementia or significant cognitive impairment aren't considered good candidates for these advanced therapies. This is because of the increased risk of cognitive decline and complicated post-procedure management.

Case example 1: essential tremor with limited functional impairment

[3:04]
Time to put on your neurologist hat. Three patients visit your clinic. Let's figure out which ones are good candidates for advanced therapies. Lena has essential tremor primarily affecting her hands. The tremor makes it difficult to write or use utensils, but her handwriting remains legible and she doesn't spill her food. The tremor doesn't interfere with other daily activities and has been stable for the past few years, but she asks if there's anything else you'd recommend to further control her tremor.

Case example 2: medication-refractory essential tremor

[3:36]
The next patient is Rosa, who complains of a tremor that affects both her arms and her head. Her tremor hasn't improved despite trying maximum doses of propranolol and primidone. The tremor significantly impairs her ability to paint, eat, and perform everyday tasks. Her social life is also limited due to the tremor.

Case example 3: essential tremor after one first-line therapy

[4:00]
And finally, Jalen presents with essential tremor that has progressively worsened over the last two years. His tremor affects both hands and his voice, making it difficult for him to type and participate in meetings at work. He was started on propranolol, which initially helped reduce the tremor, but the effect has since worn off, even at the maximum dose. He finds that social interactions are increasingly impacted, causing him frustration and embarrassment. 
Pause the video and take a moment to consider if any of these patients are an appropriate candidate for advanced therapies.

Determining who is ready for advanced essential tremor therapy

[4:38]
If you concluded that only Rosa is a good candidate, then you're correct. Let's talk about why. Rosa's tremor is significantly affecting her quality of life and hasn't responded to the two first-line options. On the other hand, Lena's tremor isn't significantly affecting her quality of life and hasn't been worsening, so holding off on treatment and continuing to monitor the tremor would be reasonable, as would trying nonpharmacological options. Jalen's tremor is interfering with his work and social interactions, but he hasn't yet tried the other first-line therapy or second-line therapies, so that would be a better next step.