Summary Of Evidence

Focused Ultrasound Thalamotomy Location Determines Clinical Benefits in Patients with Essential Tremor

Magnetic resonance guided focused ultrasound (MRgFUS) thalamotomy is a novel and minimally invasive ablative treatment for essential tremor. This study examined relationships in patients with essential tremor undergoing MRgFUS. Boutet et al. studied 66 patients with essential tremor who underwent MRgFUS between 2012 and 2017. The study assessed the Clinical Rating Scale for Tremor (CRST) scores at 3 months after the procedure and tracked the adverse effects (sensory, motor, speech, gait, and dysmetria) 1 day (acute) and 3 months after the procedure. The results indicated the area of optimal tremor response at 3 months after the procedure was identified at the posterior portion of the ventral intermediate nucleus. Lesions extending beyond the posterior region of the ventral intermediate nucleus and lateral to the lateral thalamic border were associated with increased risk of acute adverse sensory and motor effects, respectively.¹

Magnetic Resonance-Guided Focused Ultrasound Neurosurgery for Essential Tremor: A Health Technology Assessment

In this study, a systematic review of the clinical literature published up to April 11, 2017, that examined MRgFUS neurosurgery alone or compared with other interventions for the treatment of moderate to severe, medication-refractory essential tremor was performed. The review assessed the risk of bias of each study and the quality of the body of evidence according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group criteria. The inclusion criteria was that the articles were all full text publications in English, all published prior to April 11, 2017, were randomized controlled trials, systematic reviews, and nonrandomized studies of MRgFUS neurosurgery alone or MRgFUS neurosurgery compared with one or more of the following: radiofrequency thalamotomy, deep brain stimulation (unilateral or bilateral), gamma Knife thalamotomy, or control intervention.

The evidence shows that MRgFUS neurosurgery is generally safe and effective at reducing tremor severity, improving quality of life, and helping people get back to their daily activities.⁴ MRgFUS neurosurgery offers a treatment option for people with essential tremor who otherwise have none if medication fails, and it offers a noninvasive option for people considering surgery who cannot safely have invasive surgery or who find the risks of invasive surgery unacceptable.

Acute and Chronic Effects of Propranolol and Primidone in Essential Tremor (ET)

This is a 1989 study of the effects of these two drugs on ET. Koller et al. studied the acute and chronic effects of propranolol and primidone in essential tremor by administering long-acting propranolol (80 to 160 mg/d) and primidone (50 to 250 mg/d) to 50 patients. The study evaluated patients at 1, 3, 6, 9 and 12 months after treatment and assessed tremor by subjective rating by patients, clinical scoring, and tremorgraphic (accelerometer) recordings.

The results indicated that acute adverse reactions occurred in 8% with propranolol and 32% with primidone.⁵ Propranolol was without therapeutic effect in 30% and 32% had no benefit from primidone. Significant chronic side effects occurred in 17% taking propranolol and in 0% with primidone.⁵ Tolerance to drug effect occurred with chronic treatment in 12.5% of patients with propranolol and 13.0% with primidone.

Analysis of Evidence

MRgFUS is a promising new treatment approach that has attributes, positive and negative. It is noted that lesions larger than 170 mm were associated with an increased risk of acute adverse effects.³ Tremor improvement and acute adverse effects of MRgFUS for essential tremor are highly dependent on the location and size of lesions. These novel findings could refine current MRgFUS treatment planning and targeting, thereby improving clinical outcomes in patients.

Also, people with essential tremor reported positive experiences with the procedure and results experienced with MRgFUS neurosurgery.⁴ The reduction or elimination of tremor in the dominant hand increased people’s ability to perform daily tasks and improved their quality of life.

In summary, MRgFUS is a promising new treatment approach that has attributes, positive and negative, distinct from both traditional thalamotomy and DBS. Given the support for traditional thalamotomy, generally, as an alternative “if DBS is not available or practical”, and the support for MRgFUS thalamotomy, specifically, as an alternative in patients “who are not candidates for DBS” by the American Association of Neurological Surgeons (AANS), Congress of Neurological Surgeons (CNS) and the American Association of Stereotactic and Functional Neurosurgery (ASSFN), Novitas considers MRgFUS reasonable and necessary when performed within the indications and limitations of this policy.

Compliance with the provisions in this policy may be monitored and addressed through post payment data analysis and subsequent medical review audits.

History/Background and/or General Information

Historically, ultrasound has largely been performed as an extracranial diagnostic tool. However, more recently, intracranial therapeutic uses have been explored. One such use has been in the treatment of essential tremor (ET) that is refractory to more traditional treatment (e.g. medical therapy, deep brain stimulation [DBS]) through the use of focused ultrasound techniques. Magnetic-Resonance-Guided Focused Ultrasound Surgery (MRgFUS) is a non-invasive thermal ablation treatment that delivers a spherical array of converging beams using a cranial ultrasound unit that targets specific areas in the brain and heats and ablates the areas that are felt to be responsible for the ET.¹ 

Covered Indications

MRgFUS unilateral thalamotomy is considered medically reasonable and necessary in patients with all five of the following criteria:

1. Presence of medication refractory ET^2,3 defined as refractory to at least two trials of medical therapy, including at least one first-line agent (i.e. propanalol or primidone);² and
2. Presence of a moderate to severe postural or intention tremor (defined by a score greater than or equal to 2 on the clinical rating score for tremor [CRST]² or another nationally accepted clinical measure of tremor severity) of the dominant hand; and
3. The tremor is disabling (defined by a score of greater than or equal to 2 on any of the eight items in the disability subsection of the CRST² or another nationally accepted clinical measure of tremor severity); and
4. The beneficiary is not a candidate for deep brain stimulation (DBS) (e.g., advanced age, anticoagulant therapy, surgical comorbidities, or has failed DBS, but has no retained cranial implants); and
5. The beneficiary is 22 years of age or older³

Limitations

The following are considered not medically reasonable and necessary:

1. Treatment of head or voice tremor
2. Bilateral thalamotomy
3. Treatment of beneficiaries who have an advanced neurodegenerative condition²
4. Treatment of beneficiaries with unstable cardiac disease²
5. Treatment of beneficiaries suffering from depression sufficiently severe to compromise their ability to provide informed consent and limit likely clinical benefit of the treatment
6. Treatment of beneficiaries with severe cognitive impairment (defined by a score of less than 24 on the Mini–Mental State Examination)²
7. A skull density ratio (SDR) (the ratio of cortical to cancellous bone) less than 0.40²
8. Treatment when contraindications to MRI are present (e.g. metallic foreign body in eye, pacemaker etc.)

Provider Qualifications

1. Consistent with the American Society for Stereotactic and Functional Neurosurgery (ASSFN) guidelines, physicians who perform MRgFUS must possess expertise and experience in functional and stereotactic neurosurgery. Additionally, physicians who perform these services should have underdone specialized training in MRgFUS.²
   
   

Notice: Services performed for any given diagnosis must meet all of the indications and limitations stated in this policy, the general requirements for medical necessity as stated in CMS payment policy manuals, any and all existing CMS national coverage determinations, and all Medicare payment rules.

The redetermination process may be utilized for consideration of services performed outside of the reasonable and necessary requirements in this LCD.