Unilateral MRI-guided focused ultrasound thalamotomy for treatment-resistant essential tremor

Evidence-based recommendations on unilateral MRI-guided focused ultrasound thalamotomy for treatment-resistant essential tremor in adults. This involves applying ultrasound to a specific area on 1 side of the brain (thalamus).

# Recommendations
The evidence on the safety of unilateral MRI-guided focused ultrasound thalamotomy for treatment-resistant essential tremor raises no major safety concerns. However, current evidence on its efficacy is limited in quantity. Therefore, this procedure should not be used unless there are special arrangements for clinical governance, consent, and audit or research. Find out what special arrangements mean on the NICE interventional procedures guidance page.
Clinicians wishing to do unilateral MRI-guided focused ultrasound thalamotomy for treatment-resistant essential tremor should:
Inform the clinical governance leads in their NHS trusts.
Ensure that patients and their carers understand that this procedure is only done to treat tremor on 1 side of the body, and that the effect of this on the functional ability and quality of life of patients with bilateral disease is uncertain. Patients should be informed about alternative treatments, including those that can be done bilaterally. Provide patients with clear written information to support shared decision-making. In addition, the use of NICE's information for the public on unilateral MRI-guided focused ultrasound thalamotomy for treatment-resistant essential tremor is recommended.
Audit and review clinical outcomes of all patients having unilateral MRI-guided focused ultrasound thalamotomy for treatment-resistant essential tremor. NICE has identified relevant audit criteria and has developed NICE's interventional procedure outcomes audit tool (which is for use at local discretion).
Patient selection should be done by a multidisciplinary team experienced in managing essential tremor, including clinicians with specific training in the procedure.
Further research, which could include randomised controlled trials, should address patient selection, report on functional improvement and quality of life, and provide long-term follow-up data.# The condition, current treatments and procedure

# The condition
Essential tremor is the most common cause of disabling tremor and is distinct from Parkinson's disease. It typically affects the arms and hands, although it may also involve the head, jaw, tongue and legs. The cause is not known but many patients have a family history of the condition. At first, the tremor may not be present all the time. However, it gradually worsens. Purposeful movement, stress, tiredness, hunger, heightened emotions or extremes in temperature make it worse.

# Current treatments
Treatment for essential tremor includes medications such as beta blockers (for example, propranolol), anti-epileptics (for example, primidone) or sedatives (for example, clonazepam). Rarely, injections of botulinum toxin may be used.
Surgery may be considered in people whose condition has not responded adequately to best medical therapy. Surgical treatments include deep brain stimulation and radiofrequency thalamotomy.

# The procedure
This procedure is carried out with the patient lying supine inside an MRI scanner. The patient's head is shaved and a stereotactic head frame is attached. Patients are kept awake so they can report any improvement or adverse events to the operator during the procedure. However, they may be offered light sedation. Continuous MRI and thermal mapping are used to identify the target area of the brain and monitor treatment. Low power (sub-lethal) ultrasound is delivered to confirm the chosen location. Then, high-power focused ultrasound pulses are administered to irreversibly ablate target tissue. Chilled water is circulated around the head during the treatment to prevent thermal damage to the scalp caused by the increase in bone temperature. The procedure takes about 3 hours and symptom relief should be immediate.
The potential benefits of unilateral MRI-guided focused ultrasound thalamotomy are that it: is less invasive than the other existing procedures; results in a faster recovery time; and allows for testing of the effects of sub-lethal doses before ablation. However, it is only done on 1 side.