Medical Policy

This document addresses magnetic resonance imaging (MRI) guided high intensity focused ultrasound (HIFU) ablation, also known as magnetic resonance guided focused ultrasound (MRgFUS), when used to treat any non-oncologic indications, including but not limited to uterine fibroids, essential tremor (ET), or benign prostatic hyperplasia (BPH). The ultrasound beam penetrates through the soft tissues and can be focused on targeted sites, using MR for guidance and monitoring.

Note: Please see the following for additional information on the use of MRgFUS:

• SURG.00135 Renal Sympathetic Nerve Ablation for the ablation of renal sympathetic nerves using high-intensity focused ultrasound

Note: Please see the following related documents for additional information:

• CG-MED-81 Ultrasound Ablation for Oncologic Indications
• CG-SURG-91 Minimally Invasive Ablative Procedures for Epilepsy
• CG-SURG-108 Stereotactic Radiofrequency Pallidotomy
• SURG.00026 Deep Brain, Cortical, and Cerebellar Stimulation
• SURG.00149 Percutaneous Ultrasonic Ablation of Soft Tissue

Medically Necessary

1. Unilateral focused ultrasound thalamotomy is considered medically necessary for the treatment of adults with essential tremors when all of the following criteria are met:
   1. Moderate to severe tremor of the hand (as defined by a score of 2 or greater on the clinical rating scale for tremor [CRST]); and
   2. Failure of 2 or more tremor suppressant medications, as evidenced by persistent moderate to severe tremors, intolerable side effects of drug therapy or contraindications; and
   3. At least 1 of the medications failed was a first line agent (propranolol or primidone).
2. Unilateral focused ultrasound pallidotomy is considered medically necessary for the treatment of idiopathic Parkinson’s disease in individuals who meet all of the following criteria:
   1. Age 30 or older; and
   2. Unilateral pallidotomy is used as an adjunct to medication treatment of idiopathic Parkinson’s disease; and
   3. Levodopa responsive (as defined by a 30% or greater reduction in the Movement Disorder Society- Unified Parkinson's Disease Rating Scale [MDS-UPDRS] motor subscale in the on versus off levodopa medication state; and
   4. Moderate-to-severe motor complications as defined by at least one of the following:
      1. MDS-UPDRS score of 20 or greater in the meds off condition; or
      2. Motor complications on optimum medical treatment documented by at least one of the following:
         1. Dyskinesia (as defined by MDS-UPDRS item 4.2 score of 2 or greater in the meds on condition); or
         2. Motor fluctuations (as defined by MDS-UPDRS item 4.4 score of 2 or greater);
            and
   5. The individual is not a candidate for either the following procedures:
      1. Deep brain stimulation (DBS); or
      2. Radiofrequency (RF) thermoablation;
         and
   6. The absence of all of the following conditions:
      1. Central neurodegenerative disease other than Parkinson’s Disease (includes multisystem atrophy, progressive supranuclear palsy, corticobasal syndrome, dementia with Lewy bodies, and Alzheimer’s disease); or
      2. Previous deep brain stimulation; or
      3. Previous basal ganglia ablation procedure; or
      4. Coagulopathy or current anticoagulant use which cannot be reversed; or
      5. Intracranial tumor with significant anatomic distortion.

Investigational and Not Medically Necessary:

Unilateral focused ultrasound thalamotomy and unilateral focused ultrasound pallidotomy are considered investigational and not medically necessary when the criteria above are not met.

Other uses of focused ultrasound ablation are considered investigational and not medically necessary for all other non-oncologic indications, including but not limited to:

1. Bilateral staged focused ultrasound thalamotomy or pallidotomy; or
2. Benign prostatic hyperplasia; or
3. Uterine fibroids.

Summary

MRgFUS is a non-invasive treatment that uses high-intensity sound waves to destroy targeted tissue in the brain and other areas of the body. Treatment with MRgFUS is conducted with the use of several devices approved by the U.S. Food and Drug Administration (FDA), including for the treatment of uterine fibroids, ET and Parkinson’s disease in individuals who do not respond to medication. Evidence is strongest for the use of MRgFUS for unilateral thalamotomy in ET and unilateral pallidotomy in Parkinson’s disease, where studies have shown meaningful improvements in symptoms, though benefits, particularly for tremors, may lessen over time. Compared to surgical options like DBS or radiofrequency ablation, MRgFUS is less invasive but may cause more lasting side effects due to permanent tissue damage. Current use is limited to treatment of one side of the brain, though early studies are exploring bilateral treatment. While MRgFUS shows promise, especially for those unable or unwilling to undergo surgery, evidence remains limited for Parkinson’s disease over the long term. Research on uterine fibroids and other conditions suggests possible benefits, but more rigorous studies are needed before broader use is appropriate.

Discussion

Essential Tremor (ET)

The first line treatment for ET is pharmacotherapy, with propranolol and primidone considered as first line medication (Elias, 2016). Neurosurgical intervention targeted at the nucleus ventralis intermedius of the thalamus can be considered for individuals who have failed medication therapy. The targeted tissue connects the cerebellum with cortical motor pathways. Radiofrequency thalamotomy and deep brain stimulation have been used to disrupt this pathway and suppress tremors. Acceptance of these procedures by those with ET has generally been low based upon the reluctance to undergo the invasive procedures.

In July 2016, the FDA approved the ExAblate Neuro^® system (InSightec, Inc., Dallas, TX) as a unilateral treatment of idiopathic ET in adults aged 22 or older whose tremor has failed pharmacological treatment. ExAblate Neuro uses focused ultrasound to induce a unilateral thalamic lesion (thalamotomy) when the ventralis intermedius has been identified and is accessible for ablation by the device. The intent of treatment is to reduce an individual’s ET and increase motor function.

Elias and colleagues (2013) reported on the results of a feasibility trial for the ExAblate Neuro unilateral transcranial MRI-guided focused ultrasound thalamotomy to treat medication-refractory ET. The study defined medication refractory tremor as failure of treatment with at least two trials of full-dose therapeutic medication, one of which had to be a first line therapy (propranolol or primidone). In this uncontrolled pilot study, 15 individuals with severe medication-refractory ET underwent a single treatment session using the ExAblate Neuro system. Assessments were performed at baseline, 1 day, 1 week, 1 month, 3 months and 12 months following treatment, with the change in hand tremor score at 3 months being the primary clinical outcome. Hand tremor was scored using a summation of eight items which graded hand tremor and ability to perform tasks. Higher scores denoted more severe tremor, and the maximum score was 32. There was significant improvement in contralateral hand tremor from baseline (20.4 ± 5.2) to 3 months (4.3 ± 3.5) and 12 months (5.2 ± 4.8). There were no reported significant differences in ipsilateral hand tremor scores from baseline to 12 months. Paresthesias of the face or fingers were the most common reported side effects.

In 2016, Elias and colleagues published the results of a prospective, sham-controlled, double-blind, randomized trial of 76 participants evaluating MRI-guided focused ultrasound thalamotomy treatment in moderate to severe medication-refractory (tremor refractory to at least 2 agents, with at least one being propranolol or primidone) ET. Participants were assigned to active treatment, MRI-guided focused ultrasound thalamotomy, or sham treatment. Following evaluation of the primary endpoint at 3 months, the individuals in the sham group could cross over to the active treatment group. The change in hand tremor scores from baseline to 3 months was defined as the primary efficacy outcome measure. The hand tremor score was based upon components of the CRST related to hand tremor, with higher scores indicating more severe tremor. At 3 months, the mean score in the contralateral hand in the active treatment group improved by 47% compared to the sham group mean score improvement of 0.1%. At 12 months, the significant improvement over baseline persisted. There was no significant change in the tremor score in the ipsilateral hand compared to baseline. The results were similar in the sham crossover group; 19 participants who crossed over to active treatment reported a significant improvement in contralateral hand tremor at 3 and 6 months respectively. A total of 74 neurological adverse events (AEs) occurred in 56 individuals who underwent active treatment, including 38% with sensory alteration and 36% with cerebellar deficits such as dysmetria and ataxia and other gait disturbance, which persisted to 12 months at 14% and 9%, respectively.

Follow-up studies evaluated the durability of MRI-guided focused ultrasound thalamotomy 2 to 3 years following treatment. Chang and colleagues (2018) reported on the 2-year follow-up outcomes of the Elias 2016 randomized controlled trial (RCT). The mean hand tremor score initially improved by 55% (from 19.8 ± 4.9 at baseline to 8.6 ± 4.5) at 6 months post procedure. At 2 years, the mean hand tremor motor score was improved by 56% over baseline (8.8 ± 5.0; change in the score from baseline to 2 years, 11 points). At 3 years post-procedure, Halpern and colleagues (2019) evaluated outcomes of this same group. The median hand tremor motor score was stable at 56% improvement over baseline (median score of 8). In a retrospective review, Meng and associates (2018) assessed the 2-year outcomes of 37 individuals who underwent unilateral MRgFUS thalamotomy to treat moderate to severe medically refractory ET. A 42.4% (95% confidence interval [CI], 32.0%-52.9%) improvement in the baseline dominant tremor score (20.3 ± 5.0) was maintained at 2 years (43.4%: 95% CI: 27.8%-59.0%). At 1 year post-treatment, 45.7% of the individuals had significant tremor improvement; this had decreased to 35.3% at 2 years (Halpern, 2019). These follow-up studies report substantial drop-out rates, introducing the potential for retention bias into the results. Additional studies with follow-up from 3 to 5 years post-procedure report showed sustained improvement from baseline (Cosgrove, 2022; Halpern, 2019; Park, 2019; Sinai, 2019).

The International Parkinson and Movement Disorder Society (IPMDS) published an evidence-based review of ET treatments (Ferreira 2019). The task force noted that unilateral MRgFUS thalamotomy is “likely efficacious” (evidence suggests, but is not sufficient to show, that the intervention has a positive effect on studied outcomes). The task force concluded that unilateral MRgFUS thalamotomy is “possibly useful” for clinical practice.

Miller and colleagues (2022) reported on the prevalence of worsening tremor over time following MRgFUS treatment of ET. This is the phenomenon noted above in Louis’s analysis of the pivotal trial published by Elliot et al. Miller’s meta-analysis included 17 prospective studies, 3 retrospective studies and 1 RCT. Tremor was evaluated using hand tremor scores (HTS), CRST scores, or Quality of Life in Essential Tremor Questionnaire (QUEST) using pool reported effects. The analysis showed ongoing treatment benefit but decreasing treatment effect from 3 to12 months and 24 months following treatment. The authors noted that this diminishing effect might be due to heterogeneity within the studies, disease progression, or a true waning effect over time. Diminished effects have also been reported with DBS, either due to disease progression or habituation.

The American Society for Stereotactic and Functional Neurosurgery (ASSFN) position statement on MRgFUS (Pouratian, 2020) notes the following indications when using MRgFUS as a treatment option of ET:

1. Confirmed diagnosis of ET.
2. Failure to respond to, intolerance of, or medical contraindication to use of at least 2 medications for ET, 1 of which must be a first-line medication.
3. Appendicular tremor that interferes with quality of life (QoL) based on clinical history.
4. Unilateral treatment.

The ASSFN position statement notes the following contraindications to MRgFUS therapy:

1. Bilateral MRgFUS thalamotomy.
2. Contralateral to a previous thalamotomy.
3. Cannot undergo magnetic resonance imaging (MRI) because of medical reasons.
4. Skull density ratio (ratio of cortical to cancellous bone) is <0.40

The ASSFN statement also notes that there is insufficient evidence to support treatment of tremors of the head, voice or neck with MRgFUS.

In 2020, Giordano and associates published a systematic review comparing unilateral MRgFUS thalamotomy to unilateral and bilateral DBS. Studies reporting on the treatment of drug-refractory ET using DBS (n=37) or MRgFUS (n=7) were included. There were no prospective randomized studies directly comparing MRgFUS to DBS. A total of 1202 individuals were included in this study’s DBS group and 477 individuals were included in the MRgFUS group. At 14.4-16.6 months follow-up, the improvement in quality of life was significantly greater in the MRgFUS group (61.9%) compared to the DBS group (52.5%). During that follow-up period, there was a significantly higher improvement in tremor severity in the DBS group (60.1%) compared to the MRgFUS group (55.6%). While a subgroup analysis showed no differences in tremor severity between unilateral DBS therapy and MRgFUS therapy, bilateral DBS therapy was superior to both unilateral treatments. The authors asserted that bilateral DBS is the current gold standard treatment for medication-resistant ET. Bilateral staged MRgFUS thalamotomy is currently undergoing feasibility testing. MRgFUS and DBS have different complication patterns. MRgFUS is associated with a higher prevalence of gait disturbances/muscle problems, nausea and paresthesias. DBS is associated with a higher prevalence of speech disturbances and local adverse symptoms. Persistent complications are more frequent with MRgFUS than with DBS therapy. This may be due to permanent tissue destruction induced by MRgFUS compared to DBS which can be reprogrammed or turned off.

Bilateral MRgFUS in ET 

In 2022, FDA expanded the approved use of the ExAblate Neuro^® system to include treatment of the second side in individuals with ET when treated at least 9 months following treatment of the initial side. The approval was based on the pivotal, prospective, open label uncontrolled, single-arm, cohort, multicenter trial (Kaplitt, 2024). 
Campins-Romeu (2025) published the results of a prospective observational study involving 20 individuals with medication-refractory ET who had previously undergone successful unilateral MRgFUS thalamotomy and then underwent a second, staged thalamotomy on the contralateral side. Individuals were followed for 6 months after the second procedure to assess efficacy and safety outcomes. There was a 45.53% reduction in the total CRST score 6 months following the initial thalamotomy and an additional 36.22% reduction in the CRST score at 6 months following the second thalamotomy. While the authors reported promising short-term outcomes for bilateral staged MRgFUS thalamotomy in ET, the strength of the evidence remains limited due to several key factors. The small sample size and short follow-up period of only 6 months after the second procedure restrict the generalizability and durability of the results. The study also excluded individuals with pre-existing balance, speech, or cognitive issues, which skews the safety profile toward a healthier subset and may underrepresent risks in a broader population. While reductions in tremor severity and disability were statistically significant, the improvements in QOL measures were uneven across domains and did not reach significance in critical areas such as communication and work/finances. Approximately 70% of participants still reported mild AEs at 6 months, including gait instability and paresthesia, raising concerns about cumulative bilateral effects. Lacking longer-term data and comparison against standard treatments like DBS, the results are insufficient to firmly establish bilateral MRgFUS thalamotomy as a broadly applicable or definitively safer alternative.

In 2024, Kaplitt and colleagues published the results of this pivotal trial. A total of 51 individuals, out of an enrolled total of 62 individuals who had previously undergone unilateral MRgFUS at least 9 months prior, were chosen to undergo contralateral treatment. The primary endpoint was the tremor/motor score in the treated side at 3 months post procedure, as measured by the CRST (parts A and B) and AEs were evaluated and followed through 12 months. At 3 months, the mean CRST score was reduced from 17.4 to 6.4 (5.4; 95% CI: 15.9 to 18.9 and 5.3; 95% CI: 4.9-7.9; respectively, 66% reduction in the CRST parts A and B; 95% CI: 59.8-72.2; p<0.001). The improvements in scores were similar at 6 and 12 months. Functional disability (CRST part C) improved from a mean of 10.3 to 2.2 at 3 months following treatment (4.7; 95% CI: 9.0-11.6 versus 2.8; 95% CI: 1.4-2.9; respectively, a 73% improvement in CRST part C; p<0.001). The most common participant-reported AEs at 30 days were numbness or tingling, dysarthria, ataxia, unsteadiness/imbalance, dysgeusia, gait disturbance and dysphagia. AEs were categorized as mild (85%), moderate (13%), or severe (2%). The severe AE was a severe urinary tract infection related to catheter use during the procedure. In addition to self-reported AEs, assessments were completed by a speech and language pathologist. Phonation shifted from non-significantly abnormal at baseline to significantly abnormal at 1 month post procedure (1 participant) and at 6 months post procedure (3 participants). A total of 5 participants developed significant slurred/slow speech at 1 month post treatment. At 3 months, 3 participants had ongoing, significant difficulties in articulation. At 1-month post-treatment, 9 participants had significant abnormal dysphagia, at 6 months, 3 participants had ongoing significant abnormal dysphagia and 1 participant had nonsignificant abnormal dysphagia. While the reported magnitude and stability of tremor relief at 1 year was similar to the results following unilateral MRgFUS, the frequency of AEs was greater than those reported during unilateral treatment.

DBS has been considered the standard of care treatment for medically refractory ET. Radiofrequency ablation has been considered an option in individuals who are high risk candidates for DBS surgery. These procedures are associated with risks including intracerebral hemorrhage, post radiation necrosis, infections, and hardware malfunction. Adoption of these modalities by individuals with medically refractory ET has been limited due to the invasiveness of these procedures and their perceived risks. Unilateral MRgFUS has become widely accepted by the medical community as an effective minimally invasive therapy for individuals who are not candidates for, or refuse to undergo, a more invasive procedure. The evidence regarding bilateral MRgFUS is in the early stages and is limited to short-term outcomes with no data on long-term safety. The current evidence is limited by the minimal diversity of the study population and higher frequencies of AEs compared to previous studies suggest the need for further research to establish broader efficacy and safety.

Parkinson’s Disease (PD)

In 2018, the FDA expanded the approved indications for use to include “unilateral pallidotomy of patients with advanced, idiopathic PD with medication-refractory moderate to severe motor complications as an adjunct to PD medication treatment.” The approval also requires that affected individuals must be at least 30 years of age or older with the globus pallidus being identifiable and accessible by the device. The FDA has not approved the use of bilateral pallidotomy to treat PD.

In an initial pilot investigation, Bond and associates (2017) evaluated the safety and efficacy of MRgFUS thalamotomy for the treatment of medically refractory, tremor dominant PD (TDPD). In a double-blind, sham-controlled, pilot RCT, 27 individuals were treated with MRGFUS thalamotomy (n=20) or sham procedure (n=7). After 3 months, individuals in the sham procedure group were offered open-label treatment and 6 individuals underwent MRGFUS thalamotomy. The primary outcome was the change from baseline to 3 months in the treated upper limb tremor subscore. Hand tremor improved 62% (interquartile range [IQR] 22%-79%) from a baseline of 17 points (IQR 10.5-27.5) following MRgFUS thalamotomy and 22% (IQR −11% to 29%) from a baseline of 23 points (IQR 14-27) after sham procedures (p=0.04). AEs occurred in approximately 35% of all individuals treated and included finger paresthesia, ataxia, and orofacial paresthesia. At 1 year, only 14 (47%) of the original 30 individuals in the initial treatment group were available for evaluation. Of these, 13 individuals reported a positive outcome. While this initial pilot study reported positive results, this was a small study which did not reach its planned enrollment size and lost a significant portion of the treatment group at 1 year follow-up.

Krishna and associates (2023) evaluated the safety and efficacy of MRgFUS of the globus pallidus internus in individuals with PD. Individuals with PD and dyskinesias or motor fluctuations and motor impairment in the off-medication state were eligible to be included in this multicenter, prospective, double-blind, randomized, sham-controlled trial. Trial eligibility was determined for the treated side in the off-medication state by scores on the MDS-UPDRS part III or, in the on-medication state, the score on the Unified Dyskinesia Rating Scale (UDysRS). Participants were randomized to receive MRgFUS of the globus pallidus internus (n=69) or a sham procedure (n=25). The primary outcome was a response defined as a decrease or improvement of at least 3 points on either of the cited scales on the treated side without a clinically meaningful worsening in either scale at 3 months. A total of 65/69 participants (94%) in the treatment group and 22/25 (88%) in the sham group completed the 3-month assessment. At 3 months, approximately one-third of participants in the MRgFUS group were classified as having a response resulting in improved motor function and reduced dyskinesia, one-third were classified as non-responders. Approximately one-third of participants in the sham group had a response. After the 3-month evaluation, 20 individuals in the sham group elected to undergo active treatment. The 3-month outcomes of the cross-over group were similar to the initial active treatment group. The authors of the study concluded:

The procedure has recently been approved by the FDA for unilateral treatment only, whereas most patients with Parkinson’s disease have bilateral motor signs and symptoms. There are limitations of the procedure in a condition with bilateral manifestations. Unlike deep-brain stimulation, there is no opportunity to treat progressive worsening of motor symptoms. Owing to the lack of ability to modify the lesion after the procedure, operators must prioritize safety during treatment. With deep-brain stimulation, adjustments in programming can attempt to improve the balance between a reduction in motor symptoms and a reduction in stimulation-related side effects, even years after implantation.

Schrag (2023) commented that the results of the Krishna (2023) study were encouraging, but noted:

Given the nonreversible nature of the intervention and the progressive nature of the disease, it will be important to establish whether improvements in motor complications are maintained over longer periods and whether treatment results in improved overall functioning and quality of life for patients.

The long-term clinical outcomes of MRgFUS thalamotomy to treat TDPD showed that therapeutic benefits might continue up to 5 years post-procedure (Sinai, 2022). Individuals with TDPD who chose surgery over DBS at a single institution (n=26) were followed for up to 60 months. The unilateral MRgFUS thalamotomy was used to primarily alleviate tremor in the dominant hand. Immediately following treatment, tremors completely ceased in 23 of the 26 participants and there was a 90% improvement in the remaining 3 participants. The median duration of follow-up was 36 months. Seven participants (27%) were evaluated after 5 years. In the 5-year follow-up, 1 individual experienced return of tremors to the baseline level. Five other participants had a partial return of tremors. All AEs were reported within 1 week of treatment and reported as mild and transient.

Bilateral MRgFUS in PD

In 2024, Martínez-Fernández published the results of a pilot case-series study reporting on the results of staged bilateral MRgFUS subthalamotomy. Individuals who had previously undergone unilateral MRgFUS subthalamotomy with positive results and no permanent AEs were offered the opportunity to participate (n=6). This represented approximately 13% of individuals who were initially treated (6 out of 45 individuals). The AEs  reported included contralateral dyskinesia, speech disturbances, dysphagia, and imbalance. Although most symptoms were transient and speech disturbances improved, they did persist in a mild form for some individuals. There was a significant improvement in the MDS-UPDRS part III score in the off-medication state by 52.6% at 6 months after the second treatment. Secondary efficacy outcomes indicated improvements in motor features, motor complications, daily living activities, quality of life, participants’ global impression of change, and changes in dopaminergic treatment. The study offers early, short-term results from a single institution with a highly selected small group of individuals. Further research with larger sample sizes, multi-center trials, longer follow-up periods, and direct comparisons with existing treatment options are necessary to conclusively establish the procedure's appropriateness for a broader population.
Cesarano (2024) published a systematic review examining staged bilateral MRgFUS thalamotomy for ET and PD-related tremor. The authors found the procedure showed promise in reducing tremor, improving quality of life, and maintaining cognitive function, with mostly mild and transient AEs. However, the evidence base is limited and inconsistent. The review included 9 small studies (case series, retrospective and single arm) did not include any randomized controlled trials. The sizes of the included studies ranged from one to 21 participants. There was significant variability in treatment protocols, lesion targets, outcome measures, and follow-up durations. AEs, including dysarthria, gait disturbance, and sensory changes, were present in several cases, and long-term cognitive impacts were not uniformly assessed. The authors acknowledged these limitations and emphasized the need for high-quality, controlled studies. Given the small, heterogeneous, and methodologically weak evidence base, bilateral MRgFUS thalamotomy cannot yet be considered medically appropriate for widespread clinical use.

Unilateral lesioning surgery (LS) is preferred over bilateral procedures, which are associated with increased side effects. Sharma and associates (2020) note:

A major limitation of LS is increased side effects with bilateral lesions, including aphasia, dysarthria, dysphagia, and cognitive deficits about 30 to 60% for bilateral thalamotomies and hypophonia, neuropsychological, and cognitive deficits about 17% for bilateral pallidotomies.

Generally, thalamotomy is considered for tremor-predominant PD or ET, although in individuals with PD, a pallidotomy might be a better choice as it can additionally improve bradykinesia and rigidity.

Deuschl and colleagues (2022) provided the following consideration of the evidence by the European Academy of Neurology (EAN)/Movement Disorder Society (MDS) regarding MRgFUS in the treatment of PD:

This treatment is new, and only one RCT is available. The results are promising regarding the standard outcomes for advanced PD. The AEs are frequent, but longer term sequela are mild and rare. Many key questions, however, remain open regarding this treatment: Long- term data beyond 1 year are lacking. The treatment was applied unilaterally in a highly selected group of people with unilaterally dominant PD....The majority of people with advanced PD have bilateral disease, but it is unknown whether MRgFUS subthalamotomy can be safely and efficiently performed bilaterally.

Pharmacological therapy has been the primary treatment to manage symptoms in individuals with PD. DBS has been an option for individuals with disabling and medically unresponsive disease. Radiofrequency pallidotomy is considered an option in individuals who are high risk candidates for DBS surgery. DBS and radiofrequency pallidotomy are invasive procedures with potential complications such as intracerebral hemorrhage, infections, and hardware malfunction. Focused ultrasound has been evaluated as an alternative to other invasive procedures in medically refractory PD. Experts in the field advise that MRgFUS should be an option for individuals with severe, treatment-resistant, tremor predominant PD who are not candidates for DBS or radiofrequency pallidotomy.

Anatomic Distortion

The presence of masses within the enclosed space of the cranial vault present unique challenges (Sorribes, 2019). Expanding tumor mass may cause changes within the intracranial anatomy, including compression, distortion due to brain shift and traction of intracranial structures (Khan, 2013). These changes are the result of pathological processes, including tumor cells displacing adjacent healthy tissue, tumor-induced vascular abnormalities, disruption of the blood brain barrier and cerebral edema (Sorribes, 2019). Cerebrospinal fluid displacement, cerebral blood flow decrease, and changes in the parenchyma shape may result, in order to compensate for the increasing intracranial pressure (Sorribes, 2019). There is a paucity of evidence evaluating intracranial focused ultrasound therapy in the presence of significant distortion by intracranial pathology.

Other Movement Disorders

Altinel and colleagues (2019) conducted a systematic review and meta-analysis comparing lesion surgery to DBS to treat tremor related to PD, ET or multiple sclerosis. While the analysis included 15 randomized studies, only 2 studies used MRgFUS to create the lesion. The duration of follow-up in both studies was limited to 3 months. A separate analysis found no difference in tremor severity improvement between MRgFUS, DBS and other types of lesion surgery. Over the short-term 3-month follow-up period, MRgFUS was associated with higher QOL scores than DBS. This analysis was limited by heterogeneity (tremor etiology, type of lesion surgery), limited follow-up times and lack of direct comparison groups.

In 2018, Schreglmann and associates evaluated efficacy and the prevalence of persistent side effects of different lesioning techniques in the treatment of ET, PD, dystonic tremor, multiple sclerosis or lesions to the midbrain or cerebellar structures. ET was treated with MRgFUS, Gamma Knife, or radiofrequency in 6 retrospective and 7 prospective studies. The primary outcome was the change in upper limb tremor severity from baseline to follow-up, with the selected follow-up time-point as the point with the largest number of individuals retained. As the follow-up times varied, the authors controlled for an effect on follow-up duration on the effect size. The authors reported that the duration of follow-up did not have a significant influence on treatment effect size. There were no significant differences over the studied time periods with regard to the mean effect on tremor severity or the rate of persistent side effects. The authors concluded that head-to-head comparisons between DBS and MRgFUS are needed to further evaluate tremor treatment and noted:

Nevertheless, this systematic review also shows how limited the evidence base is in particular for MRIgFUS ablation in conditions other than ET. It therefore highlights the need for adequately designed prospective trials to support the existing data on safety and efficacy for established targets such as V.im. and of recently rediscovered targets within the PSA. Before that, the indiscriminate application of incisionless interventions to novel indications could potentially harm the further development of this fascinating technique.

Benign prostatic hyperplasia (BPH)

HIFU ablation is a minimally invasive procedure using a transrectal ultrasound probe to image the prostate and deliver timed bursts of heat to create coagulation necrosis in a targeted area without harming adjacent healthy tissue (Leslie, 2006). Schatzl and colleagues (2000) compared the efficacy of transurethral resection of the prostate (TURP) to four less invasive treatment options including HIFU in a small clinical trial. Randomization was attempted but could not be carried out because treatment options for each participant were limited based on specific characteristics such as prostate size, prostatic calcifications and middle lobe anatomy. The individuals who received HIFU tended to have smaller prostates and less severe symptoms than those who received TURP. A second study reported by Madersbacher and colleagues (2000) attempted to determine the long-term outcome after HIFU therapy for individuals with lower urinary tract symptoms (LUTS) due to BPH. The data collected between June 1992 and March 1995 indicated that HIFU therapy for BPH, at least in its present form, did not “stand the test of time,” as 43.8% of individuals had to undergo TURP within 4 years after initial therapy. Additional long-term studies are warranted to reliably assess the role of HIFU as an established alternative to standard treatments for BPH. In recent years, few trials evaluating the use of HIFU in BPH have been published (Garcia-Becerra, 2024).

Uterine Fibroids

In the pivotal study for the ExAblate^® 2000 (InSightec, Ltd, Dallas, TX), Stewart and colleagues studied 109 participants treated with MRgFUS and 83 participants treated with abdominal hysterectomy. The initial article published in 2004, and the follow-up article published in 2006, only reported the outcomes for the group treated with HIFU. The study’s primary outcome was change in the symptom severity score (SSS) that is part of the validated Uterine Fibroid Symptom Quality of Life Questionnaire (UFS-QOL). Symptom severity was measured on a 0 (less severe) to 100 (most severe) scale with eight questions relevant to bulk and bleeding symptoms. At the 6-month follow-up, 71% of the HIFU group achieved a 10-point or greater reduction in SSS which decreased to 51% at 12 months. It was unclear what value represented a clinically meaningful change in SSS. Furthermore, 21% of those treated by HIFU needed additional surgical treatment, and 4% underwent a repeat MRI guided HIFU within 12 months of the first treatment.

Kim and colleagues (2011) reported a 3-year follow-up on a prospective study of 40 women with symptomatic fibroids. A total of 51 fibroids were treated with MRgFUS. Clinical assessments were obtained at 3 months, 6 months, and 1, 2, and 3 years after HIFU treatment, as well as the SSS from the UFS-QOL. An MRI was performed at each follow-up to assess the efficacy of the treatment at 6 months, 1 year, 2 years, and 3 years. The mean baseline volume of treated fibroids was 336.9 cm³. The mean improvement scores for transformed SSS was 47.8 (p<0.001) and for transformed UFS-QOL was 39.8 (p<0.001) at 3 years. The mean volume decrease in treated fibroids was 32.0% (p<0.001) and in the uterus, the volume decrease was 27.7% (p<0.001) at 3 years. There were no complications. The authors noted that these results are preliminary.

Clark and colleagues (2014) conducted a systematic review of the efficacy of MRgFUS, specifically on its performance preserving fertility in women. A total of 10 studies, representing 589 women, were chosen for inclusion in the meta-analysis. Study inclusion criteria included a report of mean SSS at baseline and 6-month follow-up. The overall mean improvement in SSS 6 months after MRgFUS was estimated at 31.0% (95% CI, 23.9-38.2%). Authors concluded that, “Given the minimally invasive approach, MRgFUS could become the treatment of choice for patients desiring future fertility; however, further investigation is needed.”

Dou (2024) published a meta-analysis evaluating long-term outcomes and risk factors for reintervention following MRgFUS therapy for the treatment of uterine fibroids. The meta-analysis included data from 18 studies involving 5,216 participants. The pooled reintervention rates at 12, 24, 36, and 60 months were 1%, 7%, 19%, and 29%, respectively. The included studies had significant limitations: all included studies were observational, with no RCTs, introducing a high risk of bias and limiting the strength of the conclusions. Additionally, there was substantial heterogeneity across studies in terms of participant characteristics, guidance methods, and imaging parameters. There is no high-quality comparative data available between MRgFUS and other standard treatments like myomectomy or uterine artery embolization (UAE), making it difficult to position MRgFUS definitively within clinical practice guidelines.

Initial studies evaluated the viability and technical aspects of MRgFUS as a noninvasive treatment of symptomatic uterine fibroids (Stewart, 2003; Stewart, 2007; Taran, 2009). However, well-designed clinical studies evaluating the safety and efficacy of MRgFUS using relevant outcome measures are lacking. Evaluations continue to lack  comparisons to the current accepted treatments of uterine fibroids (Gizzo, 2014; Ikink, 2013; Inbar, 2025; Pron, 2015). Additionally, based on the prevalence of uterine fibroids, a relatively small number of women have been studied in clinical trials. The published evidence regarding MRgFUS does not adequately address the potential for regrowth of treated uterine fibroids over time, particularly beyond 3 to 5 years. In order to demonstrate MRgFUS as a safe and effective treatment option for uterine fibroids, well-designed RCTs with sufficient follow-up periods and appropriate clinical outcome measures are needed to compare therapy with alternative treatments.

The American College of Radiology (ACR) 2023 update to the Appropriateness Criteria^® document on the management of Uterine Leiomyomas now considers MRgFUS appropriate or may be appropriate in some clinical situations. The studies cited in the guideline include observational studies or studies with a limited number of participants.

The American College of Obstetricians and Gynecologists (ACOG) stated in their practice bulletin, Management of Symptomatic Uterine Leiomyomas (2021):

Limited, low-quality data suggest that magnetic resonance-guided focused ultrasound and high-intensity focused ultrasound are associated with a reduction in leiomyoma and uterine size. However, small randomized comparative trial data suggest that compared with UAE, magnetic resonance-guided focused ultrasound is associated with less improvement in symptoms and quality-of-life measures and a higher risk of reintervention.

Other Conditions

An Ontario Health Technology Assessment (2025) reviews MRgFUS for severe, treatment-refractory obsessive-compulsive disorder (OCD) and noted that therapy may reduce OCD symptoms and improve quality of life with few adverse effects. These conclusions were based on two small case series (n=17). The evidence is rated "Very low" due to small sample sizes, lack of control groups, and potential bias.

MRgFUS is being studied for a variety of conditions, including but not limited to benign thyroid nodules, chronic neuropathic pain, desmoid tumors, obsessive compulsive disorder or primary hyperparathyroidism (Chung, 2020; Henn, 2024; Jeanmonod, 2012; Jung, 2015; Kovatcheva, 2014; Martin, 2009; Monteith, 2016). These preliminary studies are in the early stages of evaluating the feasibility, efficacy and safety of the use of MRgFUS for the treatment of these conditions. Robust, well-controlled studies are needed to confirm efficacy and guide broader use.

Central Neurodegenerative Disease

Neurodegenerative diseases are progressive conditions which result in both physical and mental impairments. The common feature of all neurodegenerative diseases is neuronal death. The presenting symptoms are dependent on the type and position of the degenerated neurons within the brain. The etiology of neurodegenerative diseases is poorly understood, but there are similar features across all diseases: disrupted proteostasis, oxidative and endoplasmic reticulum stress, metabolic dysfunction, and neuroimmune system alterations (Bloomingdale, 2022). The blood-brain barrier has limited the effectiveness of potentially curative pathogenesis-targeting pharmacological therapies (Lamptey, 2022). Treatments are limited to symptom alleviation.

Neurodegenerative diseases, such as progressive supranuclear palsy were once considered a type of atypical Parkinsonism but is now categorized as a separate motor and behavioral syndrome (Boxer, 2017). Corticobasal degeneration is closely related to progressive supranuclear palsy and there appears to be considerable clinical and genetic overlap between the syndromes (Boxer, 2017). Lewy body with dementia and PD dementia are currently both characterized as being under the umbrella term Lewy body dementia. There are no curative treatments available and therapy is focused on symptom management. Management is difficult as treatment aimed at addressing one symptom may worsen other symptoms (Taylor, 2020). Taylor and colleagues (2020) describe the differences between these conditions noting:

The two diseases are demarcated clinically from one another by the so-called 1-year rule, based on the temporal onset of motor relative to cognitive symptoms (ie, in Parkinson’s disease dementia the motor symptoms precede the onset of dementia by at least one year).

There are knowledge and evidence gaps regarding the pathophysiology and treatment of central neurodegenerative disorders. The presence of atypical Parkinsonism is considered a contraindication for other established treatments of PD (Fabbri 2023; Sharma, 2020). There are no studies which evaluate the clinical outcomes of MRgFUS lesioning in treating idiopathic PD when another central neurodegenerative disease has also been diagnosed.

ET

ET is a progressive, disabling movement disorder, affecting as much as 4% of the population (Elias, 2013). ET does not reduce life expectancy but does adversely affect QOL. While there does appear to be a familial component, the cause of this disorder is not known. Medication is the initial treatment when the symptoms interfere with function and QOL, with propranolol and primidone considered first-line agents. Second-line agents, such as gabapentin or carbamazepine are considered less effective. Approximately 30- 50% of individuals treated for ET cannot tolerate or fail medication therapy. Surgical treatments include radiofrequency thalamotomy, surgical resection and deep brain stimulation. MRgFUS is considered a minimally invasive treatment option. Similar to radiofrequency thalamotomy and surgical resection, MRgFUS creates a thalamic lesion which can reduce tremor, but can also result in permanent neurologic deficits (Elias, 2016). While creation of a lesion does reduce tremor and larger lesions can result in more enduring efficacy, larger lesions have a higher incidence of side effects (Elias, 2016).

Tremor severity is quantified using a tremor rating assessment scale. Fahn-Tolosa-Marin Clinical Rating Scale and the Essential Tremor Rating Assessment Scale (TETRAS) rate tremors on a scale from 0 to 4. The initial tool, the Fahn-Tolosa-Marin Tremor clinical rating scale was not specific to ET. TETRAS, developed specifically for ET, correlates strongly with the Fahn-Tolosa-Marin Clinical Rating Scale. TETRAS was developed for use to evaluate ET severity in clinical trials and to monitor disease progression. The following table excerpt represents the upper limb tremor as defined by the Essential Tremor Rating Assessment Scale (Elble, 2012):

PD

PD is a heterogeneous neurodegenerative disorder which is associated with age (average onset age of 70), biological sex (more men than women are affected), heredity and environmental factors (increased risk with pesticide exposure). The majority of PD cases (85-90%) are categorized as idiopathic, with the remaining having a genetic or family risk (Kouli, 2018). The primary symptoms of PD are tremor, rigidity, bradykinesia and postural instability. The early presenting symptoms of PD are generally asymmetrical. The presence of atypical PD symptoms (cerebellar signs, early severe autonomic dysfunction, vertical supranuclear palsies, or cortical sensory loss) are indicative a possible alternative diagnosis (Kouli, 2018). The initial treatment of PD is generally pharmacological, such as levodopa and dopamine agonists. Deep brain stimulation (DBS) is considered the standard treatment to control symptoms in individuals with advanced disease who have not adequately responded to or are intolerant of medications. DBS typically results in improvements in motor skills, function and movement. Focused ultrasound ablation is limited to treating tremors.

BPH

BPH, the nonmalignant growth of the smooth muscle and epithelial cells within the prostate, is a common age-related manifestation. While almost all men will develop histologic BPH, this condition will not require treatment unless it is associated with subjective symptoms, such as LUTS. LUTS symptoms can be divided into two categories. Obstructive symptoms include hesitancy, straining, weak flow, prolonged voiding, partial or complete urinary retention or overflow incontinence. Irritative symptoms include frequency, urgency with urge incontinence, nocturia, and painful urination or voiding small amount (Roehrborn, 2005). The primary goal of treatment is to alter disease progression and prevent complications (AUA, 2014). If BPH has advanced to the point of causing obstruction, interventions may be aimed at removing excessive tissue and relieving the obstruction. HIFU has been proposed as a means of removing excessive prostate tissue.

Uterine Fibroids

The cause of fibroid tumors, also known as leiomyomas, of the uterus is unknown. However, it is suggested that fibroids may enlarge with estrogen therapy (such as oral contraceptives) or with pregnancy. Fibroid growth seems to depend on regular estrogen stimulation, and rarely affects women younger than 20 years of age or postmenopausal women. As long as a woman with fibroids is menstruating, the fibroids will probably continue to grow, although growth is usually quite slow.

Hysterectomy and various myomectomy procedures are considered the gold standard of treatment. However, there has been a longstanding research interest in developing minimally invasive alternatives. There has been interest in using HIFU treatment as a noninvasive approach to ablation of uterine fibroids. Treatment involves the use of focused high-intensity convergent ultrasound beam which increases the temperature within the targeted area to 60-95°C to destroy tissue without causing damage to adjacent tissue. During the procedure, individuals are typically placed under conscious sedation with or without epidural anesthesia, although general anesthesia may be used. Proposed advantages of HIFU include the noninvasive nature of the procedure that spares surrounding tissue, reducing postoperative morbidity, and hastening recovery.

The U.S. Food and Drug Administration (FDA) approved, via the Premarket Application (PMA) process, the ExAblate 2000 System for ablation of uterine fibroid tissue in pre- or peri-menopausal women with symptomatic uterine fibroids who desire a uterine sparing procedure. The 2004 FDA approval letter stated that women must have a uterine gestational size of less than 24 weeks and must have completed childbearing (FDA, 2004).

Benign prostate hyperplasia (BPH): A condition that causes an increase in the size of the prostate gland in men, commonly causing difficulty in urination; also referred to as benign prostatic hypertrophy.

Desmoid tumor: A type of benign, locally invasive fibrous tumor capable of growing anywhere in the body.

Essential tremor (ET): A chronic, incurable condition with unknown cause characterized by involuntary, rhythmic tremor of a body part, most typically the hands and arms.

High intensity focused ultrasound (HIFU): A surgical noninvasive procedure that uses focused high energy sound waves to destroy target tissues in the body.

Leiomyoma: A benign tumor that can be found in the uterus, commonly called a fibroid.

Menorrhagia: Excessive uterine bleeding occurring at the expected intervals of the menstrual periods.

MRI (magnetic resonance imaging): The use of a nuclear magnetic resonance spectrometer to produce electronic images of specific atoms and molecular structures in solids, especially human cells, tissues, and organs.

Myomectomy: A surgical procedure to remove only fibroids; is frequently the chosen treatment for premenopausal women who want to bear more children, because it usually can preserve fertility.

Neurodegenerative Disease: Progressive age-related disease when the neurons in the central nervous system or the peripheral nervous system lose function and die. The most common diseases are Alzheimer’s disease and PD.

Uterine Fibroids: Benign fibrous tissue collected in the uterine wall.

Ventralis intermediate nucleus of the thalamus (Vim): A part of the brain involved with movement.

The following codes for treatments and procedures applicable to this document are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services may be Medically Necessary when criteria are met:

When services are Investigational and Not Medically Necessary:
For the procedure code listed above when criteria are not met or for a staged bilateral procedure, or for all other non-oncologic diagnoses.

When services are Investigational and Not Medically Necessary:

When services are also Investigational and Not Medically Necessary:
When the code describes a procedure indicated in the Position Statement section as investigational and not medically necessary.

Peer Reviewed Publications:

1. Altinel Y, Alkhalfan F, Qiao N, Velimirovic M. Outcomes in lesion surgery versus deep brain stimulation in patients with tremor: a systematic review and meta-analysis. World Neurosurg. 2019; 123:443-452.e8.
2. Avedian RS, Bitton R, Gold G, et al. Is MR-guided high-intensity focused ultrasound a feasible treatment modality for desmoid tumors? Clin Orthop Relat Res. 2016; 474(3):697-704.
3. Bachmann G. Expanding treatment options for women with symptomatic uterine leiomyomas: timely medical breakthroughs. Fertil Steril. 2006; 85(1):46-47.
4. Bloomingdale P, Karelina T, Ramakrishnan V, et al. Hallmarks of neurodegenerative disease: a systems pharmacology perspective. CPT Pharmacometrics Syst Pharmacol. 2022; 11(11):1399-1429.
5. Bond AE, Shah BB, Huss DS, et al. Safety and efficacy of focused ultrasound thalamotomy for patients with medication-refractory, tremor-dominant Parkinson disease: a randomized clinical trial. JAMA Neurol. 2017; 74(12):1412-1418.
6. Boxer AL, Yu JT, Golbe LI, et al. Advances in progressive supranuclear palsy: new diagnostic criteria, biomarkers, and therapeutic approaches. Lancet Neurol. 2017; 16(7):552-563.
7. Campins-Romeu M, Conde-Sardón R, Sastre-Bataller I, et al. Safety and efficacy of bilateral staged focused ultrasound thalamotomy in refractory essential tremor. Brain Commun. 2025; 7(3):fcaf168.
8. Cesarano S, Saporito G, Sucapane P, et al. Staged magnetic resonance-guided focused ultrasound thalamotomy for the treatment of bilateral essential tremor and Parkinson's disease related tremor: a systematic review and critical appraisal of current knowledge. Front Neurol. 2024; 15:1409727.
9. Chang JW, Park CK, Lipsman N, et al. A prospective trial of magnetic resonance-guided focused ultrasound thalamotomy for essential tremor: results at the 2-year follow-up. Ann Neurol. 2018; 83(1):107-114.
10. Chung SR, Baek JH, Suh CH, et al. Efficacy and safety of high-intensity focused ultrasound (HIFU) for treating benign thyroid nodules: a systematic review and meta-analysis. Acta Radiol. 2020; 61(12):1636-1643.
11. Clark NA, Mumford SL, Segars JH. Reproductive impact of MRI-guided focused ultrasound surgery for fibroids: a systematic review of the evidence. Curr Opin Obstet Gynecol. 2014; 26(3):151-161.
12. Cosgrove GR, Lipsman N, Lozano AM, et al. Magnetic resonance imaging-guided focused ultrasound thalamotomy for essential tremor: 5-year follow-up results. J Neurosurg. 2022; 138(4):1028-1033.
13. Dou Y, Zhang L, Liu Y, et al. Long-term outcome and risk factors of reintervention after high intensity focused ultrasound ablation for uterine fibroids: a systematic review and meta-analysis. Int J Hyperthermia. 2024;41(1):2299479.
14. Elias WJ, Huss D, Voss T, et al. A pilot study of focused ultrasound thalamotomy for essential tremor. N Engl J Med. 2013; 369(7):640-648.
15. Elias WJ, Lipsman N, Ondo WG, et al. A randomized trial of focused ultrasound thalamotomy for essential tremor. N Engl J Med. 2016; 375(8):730-739.
16. Elble R, Comella C, Fahn S, et al. Reliability of a new scale for essential tremor. Mov Disord. 2012; 27(12):1567-1569.
17. Fabbri M, Barbosa R, Rascol O. Off-time treatment options for Parkinson's Disease. Neurol Ther. 2023; 12(2):391-424.
18. Ferreira JJ, Mestre TA, Lyons KE, et al.; MDS Task Force on Tremor and the MDS Evidence Based Medicine Committee. MDS evidence-based review of treatments for essential tremor. Mov Disord. 2019; 34(7):950-958.
19. Frieben RW, Lin HC, Hinh PP, et al. The impact of minimally invasive surgeries for the treatment of symptomatic benign prostatic hyperplasia on male sexual function: a systematic review. Asian J Androl. 2010; 12(4):500-508.
20. Garcia-Becerra CA, Soltero-Molinar V, Arias-Gallardo MI, et al. A systematic review and single-arm meta-analysis on the efficacy of high-intensity, focused ultrasound for benign prostatic hyperplasia treatment: a forgotten option? Cureus. 2024; 16(7):e65384.
21. Giordano M, Caccavella VM, Zaed I, et al. Comparison between deep brain stimulation and magnetic resonance-guided focused ultrasound in the treatment of essential tremor: a systematic review and pooled analysis of functional outcomes. J Neurol Neurosurg Psychiatry. 2020; 91(12):1270-1278.
22. Gizzo S, Saccardi C, Patrelli TS, et al. Magnetic resonance-guided focused ultrasound myomectomy: safety, efficacy, subsequent fertility and quality-of-life improvements, a systematic review. Reprod Sci. 2014; 21(4):465-476.
23. Halpern CH, Santini V, Lipsman N, et al. Three-year follow-up of prospective trial of focused ultrasound thalamotomy for essential tremor. Neurology. 2019; 93(24):e2284-e2293.
24. Harary M, Segar DJ, Hayes MT, Cosgrove GR. Unilateral thalamic deep brain stimulation versus focused ultrasound thalamotomy for essential tremor. World Neurosurg. 2019; 126:e144-e152.
25. Henn MC, Smith HD, Lopez Ramos CG, et al. A systematic review of focused ultrasound for psychiatric disorders: current applications, opportunities, and challenges. Neurosurg Focus. 2024; 57(3):E8.
26. Iacopino DG, Gagliardo C, Giugno A, et al. Preliminary experience with a transcranial magnetic resonance-guided focused ultrasound surgery system integrated with a 1.5-T MRI unit in a series of patients with essential tremor and Parkinson's disease. Neurosurg Focus. 2018; 44(2):E7.
27. Ikink ME, Voogt MJ, Verkooijen HM, et al. Mid-term clinical efficacy of a volumetric magnetic resonance-guided high-intensity focused ultrasound technique for treatment of symptomatic uterine fibroids. Eur Radiol. 2013; 23(11):3054-3061.
28. Inbar Y, Rabinovici J, Sverdlove R, et al. Long-term outcomes and re-intervention rates in women undergoing MRI-guided focused ultrasound (MRgFUS) for uterine fibroids: a 7-year follow-up study. J Assist Reprod Genet. 2025; 42(4):1191-1196.
29. Jeanmonod D, Werner B, Morel A, et al. Transcranial magnetic resonance imaging-guided focused ultrasound: noninvasive central lateral thalamotomy for chronic neuropathic pain. Neurosurg Focus. 2012; 32(1):E1.
30. Ji Y, Hu K, Zhang Y, et al. High-intensity focused ultrasound (HIFU) treatment for uterine fibroids: a meta-analysis. Arch Gynecol Obstet. 2017; 296(6):1181-1188.
31. Jung HH, Chang WS, Rachmilevitch I, et al. Different magnetic resonance imaging patterns after transcranial magnetic resonance-guided focused ultrasound of the ventral intermediate nucleus of the thalamus and anterior limb of the internal capsule in patients with essential tremor or obsessive-compulsive disorder. J Neurosurg. 2015; 122(1):162-168.
32. Kaplitt MG, Krishna V, Eisenberg HM, et al. Safety and efficacy of staged, bilateral focused ultrasound thalamotomy in essential tremor: an open-label clinical trial. JAMA Neurol. 2024; 81(9):939-946.
33. Khan RB, Merchant TE, Boop FA, et al. Headaches in children with craniopharyngioma. J Child Neurol. 2013; 28(12):1622-1625.
34. Kim HS, Baik JH, Pham LD, Jacobs MA. MR-guided high-intensity focused ultrasound treatment for symptomatic uterine leiomyomata: long-term outcomes. Acad Radiol. 2011; 18(8):970-976.
35. Kouli A, Torsney KM, Kuan WL. Parkinson’s Disease: etiology, neuropathology, and pathogenesis. In: Stoker TB, Greenland JC, editors. Parkinson’s Disease: Pathogenesis and Clinical Aspects [Internet]. Brisbane (AU): Codon Publications; 2018 Dec 21. Chapter 1.
36. Kovatcheva R, Vlahov J, Stoinov J, et al. US-guided high-intensity focused ultrasound as a promising non-invasive method for treatment of primary hyperparathyroidism. Eur Radiol. 2014; 24(9):2052-2058.
37. Krishna V, Fishman PS, Eisenberg HM, et al. Trial of globus pallidus focused ultrasound ablation in Parkinson's disease. N Engl J Med. 2023; 388(8):683-693.
38. Krishna V, Sammartino F, Agrawal P, et al. Prospective tractography-based targeting for improved safety of focused ultrasound thalamotomy. Neurosurgery. 2019; 84(1):160-168.
39. Lamptey RNL, Chaulagain B, Trivedi R, et al. A review of the common neurodegenerative disorders: current therapeutic approaches and the potential role of nanotherapeutics. Int J Mol Sci. 2022; 23(3):1851.
40. Lennon JC, Hassan I. Magnetic resonance-guided focused ultrasound for Parkinson's disease since ExAblate, 2016-2019: a systematic review. Neurol Sci. 2021; 42(2):553-563.
41. Leslie TA, Kennedy JE. High-intensity focused ultrasound principles, current uses, and potential for the future. Ultrasound Q. 2006; 22(4):263-272.
42. Lipsman N, Schwartz ML, Huang Y, et al. MR-guided focused ultrasound thalamotomy for essential tremor: a proof-of-concept study. Lancet Neurol. 2013; 12(5):462-468.
43. Louis ED. Treatment of medically refractory essential tremor. N Engl J Med. 2016; 375(8):792-793.
44. Madersbacher S, Schatzl G, Djavan B, et al. Long-term outcome of transrectal high-intensity focused ultrasound therapy for benign prostatic hyperplasia. Eur Urol. 2000; 37(6):687-694.
45. Martin E, Jeanmonod D, Morel A, et al. High-intensity focused ultrasound for noninvasive functional neurosurgery. Ann Neurol. 2009; 66(6):858-861.
46. Martínez-Fernández R, Natera-Villalba E, Rodríguez-Rojas R, et al. Staged bilateral MRI-guided focused ultrasound subthalamotomy for Parkinson Disease. JAMA Neurol. 2024; 81(6):638-644.
47. Meng Y, Solomon B, Boutet A, et al. Magnetic resonance-guided focused ultrasound thalamotomy for treatment of essential tremor: a 2-year outcome study. Mov Disord. 2018; 33(10):1647-1650.
48. Miller WK, Becker KN, Caras AJ, et al. Magnetic resonance-guided focused ultrasound treatment for essential tremor shows sustained efficacy: a meta-analysis. Neurosurg Rev. 2022; 45(1):533-544.
49. Monteith S, Snell J, Eames M, et al. Transcranial magnetic resonance-guided focused ultrasound for temporal lobe epilepsy: a laboratory feasibility study. J Neurosurg. 2016:125(8):1557-1564.
50. Park YS, Jung NY, Na YC, Chang JW. Four-year follow-up results of magnetic resonance-guided focused ultrasound thalamotomy for essential tremor. Mov Disord. 2019; 34(5):727-734.
51. Rabinovici J, Inbar Y, Revel A, et al. Clinical improvement and shrinkage of uterine fibroids after thermal ablation by magnetic resonance-guided focused ultrasound surgery. Obstet Gynecol. 2007; 30(5):771-777.
52. Roehrborn CG. Benign prostatic hyperplasia: an overview. Rev Urol. 2005; 7(Suppl 9):S3-S14.
53. Schatzl G, Madersbacher S, Djavan B, et al. Two-year results of transurethral resection of the prostate versus four ‘less invasive’ treatment options. Eur Urol. 2000; 37(6):695-701.
54. Schrag A. Focused ultrasound ablation of the globus pallidus internus for Parkinson's disease. N Engl J Med. 2023; 388(8):759-760.
55. Schreglmann SR, Krauss JK, Chang JW, et al. Functional lesional neurosurgery for tremor: a systematic review and meta-analysis. J Neurol Neurosurg Psychiatry. 2018; 89(7):717-726.
56. Sharma VD, Patel M, Miocinovic S. Surgical treatment of Parkinson's Disease: devices and lesion approaches. Neurotherapeutics. 2020; 17(4):1525-1538.
57. Sinai A, Nassar M, Eran A, et al. Magnetic resonance-guided focused ultrasound thalamotomy for essential tremor: a 5-year single-center experience. J Neurosurg. 2019: 1-8.
58. Sinai A, Nassar M, Sprecher E, et al. Focused ultrasound thalamotomy in tremor dominant Parkinson's Disease: long-term results. J Parkinsons Dis. 2022; 12(1):199-206.
59. Sorribes IC, Moore MNJ, Byrne HM, Jain HV. A biomechanical model of tumor-induced intracranial pressure and edema in brain tissue. Biophys J. 2019; 116(8):1560-1574.
60. Stacy MA, Elble RJ, Ondo WG, et al.; TRS study group. Assessment of interrater and intrarater reliability of the fahn-tolosa-marin tremor rating scale in essential tremor. Mov Disord. 2007; 22(6):833-838.
61. Stewart EA, Gedroyc WM, Tempany CM, et al. Focused ultrasound treatment of uterine fibroid tumors: safety and feasibility of a noninvasive thermoablative technique. Am J Obstet Gynecol. 2003; 189(1):48-54.
62. Stewart EA, Gostout B, Rabinovici J, et al. Sustained relief of leiomyoma symptoms by using focused ultrasound surgery. Obstet Gynecol. 2007; 110(2 Pt 1):279-287.
63. Stewart EA, Rabinovici J, Tempany CM, et al. Clinical outcomes of focused ultrasound surgery for the treatment of uterine fibroids. Fertil Steril. 2006; 85(1):22-29.
64. Taran FA, Tempany CM, Regan L, et al. Magnetic resonance-guided focused ultrasound (MRgFUS) compared with abdominal hysterectomy for treatment of uterine leiomyomas. Ultrasound Obstet Gynecol. 2009; 34(5):572-578.
65. Taylor JP, McKeith IG, Burn DJ, et al. New evidence on the management of Lewy body dementia. Lancet Neurol. 2020; 19(2):157-169.
66. Welton T, Cardoso F, Carr JA, et al. Essential tremor. Nat Rev Dis Primers. 2021; 7(1):83.
67. Yuen J, Miller KJ, Klassen BT, et al. Hyperostosis in combination with low skull density ratio: a potential contraindication for magnetic resonance imaging-guided focused ultrasound thalamotomy. Mayo Clin Proc Innov Qual Outcomes. 2021; 6(1):10-15.

Government Agency, Medical Society and Other Authoritative Publications:

1. American College of Obstetricians and Gynecologists. ACOG Practice Bulletin No. 228. Management of symptomatic uterine leiomyomas. 2021.
2. Deuschl G, Antonini A, Costa J, et al. European Academy of Neurology/Movement Disorder Society - European Section guideline on the treatment of Parkinson's disease: I. Invasive therapies. Eur J Neurol. 2022; 29(9):2580-2595.
3. Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). Other treatments for fibroids. Last Reviewed: November 2, 2018. Available at: http://www.nichd.nih.gov/health/topics/uterine/conditioninfo/treatments/Pages/radiological.aspx. Accessed on June 26, 2025.
4. Exablate Neuro, Miami, FL. Insightec; Revised March 2024. Available at: file:///C:/Users/aa00763/Downloads/PUB41002923_Exablate-Neuro-IFP-USA_Rev12_FINAL2.pdf. Accessed on June 26, 2025.
5. Expert Panel on Interventional Radiology; Makary MS, Zane K, Hwang GL, et al. ACR apropriateness criteria^® management of uterine Fibroids: 2023 update. J Am Coll Radiol. 2024; 21(6S):S203-S218.
6. Health Quality Ontario. Magnetic resonance-guided focused ultrasound neurosurgery for essential tremor: a health technology assessment. Ont Health Technol Assess Ser. 2018; 18(4):1-141.
7. Ontario Health (Quality). magnetic resonance-guided focused ultrasound neurosurgery for treatment-refractory obsessive-compulsive disorder: a health technology assessment. Ont Health Technol Assess Ser. 2025; 25(1):1-123.
8. Pouratian N, Baltuch G, Elias WJ, Gross R. American Society for Stereotactic and Functional Neurosurgery position statement on magnetic resonance-guided focused ultrasound for the management of essential tremor. Neurosurgery. 2020; 87(2):E126-E129.
9. Pron G. Magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU) treatment of symptomatic uterine fibroids: an evidence-based analysis. Ont Health Technol Assess Ser. 2015; 15(4):1-86.
10. U.S. Food and Drug Administration (FDA) Center for Devices and Radiologic Health (CDRH) 510 (k) Premarket Notification Database. InSightec Exablate Neuro. Summary of Safety and Effectiveness. No. P150038. Rockville, MD: FDA. July 11, 2016. Available at http://www.accessdata.fda.gov/cdrh_docs/pdf15/P150038B.pdf. Accessed on June 26, 2025.

1. American Parkinson Disease Association (APDA). Parkinson’s disease vs. Parkinsonism: What’s the difference? December 18, 2018. Available at: https://www.apdaparkinson.org/article/atypical-parkinsonism/. Accessed on June 26, 2025.
2. National Institute of Health (NIH): National Institute of Diabetes and Digestive and Kidney Diseases. Prostate enlargement: benign prostatic hyperplasia. June 2024. Available at: https://www.niddk.nih.gov/health-information/urologic-diseases/prostate-problems/prostate-enlargement-benign-prostatic-hyperplasia. Accessed on June 26, 2025.
3. NIH: National Institute of Environmental Health Sciences. Neurodegenerative diseases. Last reviewed June 9, 2022. Available at: https://www.niehs.nih.gov/research/supported/health/neurodegenerative/index.cfm. Accessed on June 26, 2025.
4. NIH: National Institute of Neurological Disorders and Stroke (NINDS). Accessed on June 26, 2025.
   • Deep brain stimulation for movement disorders. Available at: https://www.ninds.nih.gov/health-information/disorders/deep-brain-stimulation-movement-disorders?search-term=essential%20tremor.
   • Parkinson’s disease. Available at: https://www.ninds.nih.gov/health-information/disorders/parkinsons-disease?search-term=essential%20tremor.
5. U.S. National Library of Medicine. Uterine fibroids. Available at: http://www.nlm.nih.gov/medlineplus/ency/article/000914.htm. Accessed on June 26, 2025.

Estrogen Therapy
ExAblate 2000 System
ExAblate Neuro
Fibroids
Myomectomy
Thalamotomy

The use of specific product names is illustrative only. It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.