MRgFUS is an ‘incisionless’ procedure that is performed while the patient lies awake in an MRI scanner over a 3-4 hour period. The patient wears a special frame on the head, and ultrasound waves are ‘focused’ through the skull (without any cut to the skin or bone) into the thalamus in the brain (the same target used by deep brain stimulation for tremor). The ultrasound waves heat up and permanently disrupt the tissue, creating a ‘lesion’ in the thalamus. The lesion reduces the abnormal brain signals that cause tremor.

Focused ultrasound is very effective at reducing tremor on one side of the body. The treatment response is maximal in the first days and weeks. There is a subsequent waning of benefit over three months before stabilisation (e.g. at around 75% of the maximal initial benefit). Disease progression can also occur over the long term and the focused ultrasound lesion is not adjustable and programmable unlike DBS. Most patients experience temporary gait imbalance for several weeks (and sometimes several months) after the procedure. Around 5% of patients experience a degree of permanent gait imbalance or a patch of numbness (e.g. on the face or hand). There is around a 1% risk of another permanent neurological deficit such as weakness.  

 The two main advantages of focused ultrasound over deep brain stimulation, are 1) No ‘surgery’ is needed, that is, there is no cut to the skin or skull, and 2) No implanted hardware is required.  Because of these reasons, patients recover very quickly and can usually go home soon after the procedure.

 The disadvantages of focused ultrasound compared with deep brain stimulation, are 1) It can usually only be performed for tremor on one side of the body (DBS can treat tremor on both sides) and 2) It creates a permanent lesion which is not adjustable (where-as DBS can be adjusted over time to improve tremor that may progress over time and to reduce any side effects).