MRI-guided focussed ultrasound (MRgFUS) is a novel therapeutic modality that is under evaluation for a variety of Neurological conditions. It has recently become available in Australia for the treatment of severe medication refractory tremor and has gained substantial interest given that it facilitates the performance of neurosurgical procedures without the requirement to open the skull; so called “incisionless” surgery.
What does the technique involve?
MRgFUS involves the delivery of focussed ultrasound waves to specific brain targets. Much like a magnifying glass focussing the sun’s rays on to a specific point, focussed ultrasound waves can be used to cause strategic lesions in brain circuitry associated with abnormal neurological activity such as tremor.
How is the procedure performed?
MRgFUS involves the attachment of a localising frame to the skull which is then fixed to the ultrasound delivering apparatus. Procedures are performed with the patient awake.
Low intensity ultrasound activity is performed on a trial basis to optimize targeting prior to the delivery of the definitive treatment.
Procedures take around 4 hours.
What is the scope of use?
Currently, MRgFUS is limited to treatment on one side of the brain (unilateral lesions) treating Essential tremor on the other side of the body.
What is the evidence for the efficacy of the therapy?
The gold standard for evaluating new surgical therapies is a sham controlled study. Here, half of patients think go through a sham procedure – i.e. they go through all of the steps of the procedure but the therapy is not administered. Results in these patients can then be compared to those who have undergone the bona fide procedure.
In an international sham-controlled study involving 76 patients, treated patients experienced a 47% improvement in tremor scores at 3 months with maintained benefit at 1 year. More recent case series data has demonstrated persistent unilateral benefit at 4 years.
Trials evaluating the safety and efficacy of bilateral MRgFUS lesions (both sides of the brain) are currently underway.
Are there other indications for MRgFUS?
MRgFUS is also being examined in clinical trials for Tremor, dyskinesia and motor fluctuations in Parkinson’s disease and other tremor disorders.
Dr Silberstein provides consultative services for all medical and interventional treatment modalities for tremor.