Is ultrasound therapy a treatment option for essential tremor?

Ultrasound Therapy for Essential Tremor

Direct Answer

Yes, magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy is an established and effective treatment option for essential tremor, specifically indicated for patients who have failed at least two medications (including a first-line agent) and have significant functional disability. 1

Treatment Algorithm for Essential Tremor

First-Line Approach

• Initiate pharmacological treatment with propranolol (80-240 mg/day) or primidone only when tremor interferes with function or quality of life 2, 3
• These medications are effective in up to 70% of patients 2
• Allow 2-3 months for primidone to demonstrate clinical benefit 2

When to Consider MRgFUS Thalamotomy

• Patient must have failed treatment with at least 2 medications, including a first-line agent (propranolol or primidone), due to lack of efficacy, intolerance, or medical contraindication 1
• Appendicular tremor must significantly interfere with quality of life 1
• Consider MRgFUS as the preferred surgical option for unilateral tremor or patients with medical comorbidities due to its superior safety profile 1

Efficacy Data

Tremor Reduction

• MRgFUS demonstrates 56% sustained tremor improvement at 4 years 2, 1
• At 3 months, tremor/motor scores improve by approximately 66% 4
• Immediate tremor reduction occurs in the treated hand, with 89.4% reduction at 1 month and 81.3% at 3 months in early studies 5

Functional Outcomes

• Disability scores improve significantly, with sustained improvements in postural tremor and action tremor 1
• Quality of life improvements are substantial and durable 6

Safety Profile: Critical Advantage Over Other Surgical Options

MRgFUS has a markedly lower complication rate (4.4%) compared to radiofrequency thalamotomy (11.8%) and deep brain stimulation (21.1%) 2, 1, 3

Common Adverse Effects

• Early adverse effects include gait disturbance (36%) and paresthesias (38%), which decrease to 9% and 14% respectively by 1 year 2
• Most adverse events (98.4%) are mild or moderate, with more than 50% resolving by 1 year 2
• Serious adverse events are rare (1.6%) 2
• Transient sensory, cerebellar, motor, and speech abnormalities can occur, with persistent paresthesias in some patients 6

Lesion-Related Complications: Important Pitfall

• Larger lesion volumes and inferolateral lesion margins are associated with higher incidence of motor-related adverse events 7
• Irregular lesion tails extending into the internal capsule are strongly associated with adverse events (22 of 23 patients with irregular tails experienced at least one adverse event) 7
• Rapid rise in power delivery and temperature increases lesion size and potentially adverse events 7

Absolute Contraindications

MRgFUS thalamotomy cannot be performed in patients with: 2, 1, 3

• Inability to undergo MRI for medical reasons
• Skull density ratio <0.40
• Bilateral treatment needs (contraindicated bilaterally or contralateral to a previous thalamotomy)
• Previous contralateral thalamotomy

Bilateral Tremor Considerations

• For bilateral tremor involvement, deep brain stimulation (DBS) should be considered instead of MRgFUS, as bilateral MRgFUS is contraindicated 1
• Recent evidence from staged bilateral procedures shows efficacy, but adverse events including dysarthria, ataxia, and speech difficulties are more common, though mostly mild and transient 4
• DBS offers adjustable, reversible tremor control that can be optimized over time, making it preferable for bilateral cases 2

Technical Considerations

• The ventral intermediate nucleus (VIM) of the thalamus is the established target 2
• Treatment parameters matter: higher maximum power, rapid rise to high-power delivery, and rapid temperature rise predict larger lesion volumes 7
• Real-time MRI guidance allows target interrogation before creating permanent ablation 4

Comparison to Deep Brain Stimulation

When to Choose MRgFUS Over DBS

• Unilateral tremor 1
• Presence of medical comorbidities 2, 1
• Patient preference for non-implantable, non-adjustable treatment
• Lower complication rate is priority 1, 3

When to Choose DBS Over MRgFUS

• Bilateral tremor involvement 2, 1
• Relatively young patients who may benefit from adjustable treatment 2
• Contraindications to MRI 2, 3
• Skull density ratio <0.40 2, 1, 3