Interventional procedure overview of MRI-guided focused ultrasound subthalamotomy for treating Parkinson's

What the procedure involves

MRI-guided focused ultrasound subthalamotomy is a minimally invasive procedure that aims to treat some of the symptoms of Parkinson's.

This outpatient procedure is done with the patient lying supine inside an MRI scanner for several hours. The patient's head is shaved and a stereotactic head frame is attached. The person is usually kept awake during the procedure so they can be regularly assessed by the treating physician to evaluate the clinical response (improvement in symptoms or adverse events). Some people may be offered light sedation.

Real-time MRI guidance and thermal mapping are used to identify and adjust the target area of the brain (the subthalamic nucleus) precisely and continuously monitor treatment. Low-power ultrasound is delivered to confirm the location.

Then, several high-power focused ultrasound pulses are delivered to ablate tissue in the subthalamic nucleus (in the dorsolateral motor region and above, and mediodorsally to affect the pallidothalamic tract). The energy released and the location of the ultrasound focus are monitored in real time during the procedure by MRI thermometry and adjusted to reach above the definitive ablation temperature (of 55°C) according to clinical response.

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 is considered finished when there is sufficient clinical improvement, considering the total amount of energy delivered and the number of sonications. The procedure takes about 2 hours and symptom relief should be immediate.