The ET Treatment Comparison Study We’ve Been Waiting For!

Whenever a new treatment for a disease or condition becomes available to patients, there will inevitably be skeptics and doubters. “If it’s so good, why haven’t we heard about it?” “It hasn’t been around all that long – how do we know it’s effective?” “How does it stack up against standard treatments?” These questions and more are being asked about MRI-guided Focused Ultrasound (MRgFUS), a new treatment to control the hand tremors that result from Essential Tremor (ET).

When ET hand tremors become so severe that they impair the ability to function and are unresponsive to medication, quality of life is dramatically reduced. Sometimes, medications like primidone or propranolol initially help, but dosages gradually increase to the point where side effects are undesirable or intolerable. What choices remain?

Three conventional neurosurgical interventions

Over the last 30-40 years, two invasive neurosurgical interventions (and one noninvasive form of radiation) were created to interrupt dysfunctional brain signals before they can reach the hands. Over time, they established a track record for success. All three methods are unilateral (one side) treatments because they are directed only to the area that controls the dominant hand. This approach can restore sufficient quality of life yet minimize side effect risks.

The three established conventional approaches are:

  1. Radiofrequency thalamotomy (RF thalamotomy) – A slender radiofrequency-generating probe inserted through a hole in the skull into the small area of the thalamus deep in the brain that relays tremor signals to the motor cortex, and immediately destroys that area with intense heat
  2. Stereotactic radiosurgery (Gamma Knife) – Beams of radioactivity are focused on the small area of the thalamus to destroy it with the effects of radiation (not heat). The treatment is not immediate but takes several weeks to achieve tremor control as the area gradually dies off.
  3. Deep Brain Stimulation (DBS) – A two-part surgery involving implanting electrodes through a hole in the skull into the same area of the thalamus (neurosurgery), and another surgery to place a “powerpack” in the chest area to wire into the electrodes through the neck.
  4. MRI-guided Focused Ultrasound (MRgFUS) – the “newcomer”

    In 2013, results of a pilot study showing that beams of non-radioactive ultrasound could be noninvasively focused to destroy the thalamus area were published. The outcomes were so encouraging (immediate tremor control, minimal transient side effects) that a larger study was designed. This second study met Level I standards of research (controlled, randomized, double-blind) making it the only ET procedure submitted to such rigorous trial standards. Not only were the outcomes as good (or better) than the previous trial, but the investigators ended the study early and offered the treatment to the control group members who were only getting a “sham procedure” (identical in method but not using active ultrasound). The study was published in 2016, and shortly after the FDA approved the treatment for ET hand tremors. Naturally, the skeptics wanted to know how the results stood up to RF thalamotomy, Gamma Knife, and DBS, but patience was needed for enough MRgFUS patients to be treated to compare them all in terms of effectiveness and short-term improved quality of life (MRgFUS has not been around long-term yet).

    The first comparison article is here

    Finally, the first literature review of all four treatments has been published, thanks to a British team of medical analysts. Langford, et al (2018)i identified 46 previously published papers that contained the pertinent data on RF thalamotomy, stereotactic radiosurgery, DBS and MRgFUS. They found no difference in efficacy or quality of life, and wrote that the captured studies demonstrate that:

    …radiofrequency thalamotomy, DBS, stereotactic radiosurgery, and MRgFUS all exhibit clinical efficacy, with variation in onset and duration of tremor relief, and are each associated with a unique safety profile. … This study provides preliminary evidence that MRgFUS could elicit similar short-term tremor- and HRQoL-related benefits to DBS, the current standard of care, and allowed for the first robust statistical comparison between these interventions.

    While this is the first comparison, it won’t be the last as the long-term results of MRgFUS will take time to accrue. At Sperling Neurosurgery Associates, we are confident that this treatment is here to stay. In addition to its transformative power, it has the added benefits of being a noninvasive outpatient treatment with immediate results. In that sense, invasive DBS and “gradually effective” stereotactic radiosurgery simply can’t compare.

    iLangford BE, Ridley CJA, Beale RC, Caseby SCL et al. Focused Ultrasound Thalamotomy and Other Interventions for Medication-Refractory Essential Tremor: An Indirect Comparison of Short-Term Impact on Health-Related Quality of Life. Value Health. 2018 Oct;21(10):1168-1175.

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