The Use of Focused Ultrasound Ablation for Movement Disorders

Abstract

Focused ultrasound ablation achieves selective thermal lesioning of the thalamic and basal ganglia targets using real-time MR imaging guidance. It is US Food and Drug Administration-approved to treat essential tremor and Parkinson's disease tremor, fluctuations, and dyskinesias. Patients often seek focused ultrasound treatment because symptom relief is immediate, and hardware implantation is not required. This review summarizes the current and potential future application of focused ultrasound ablation to treat movement disorders. We also discuss the ongoing research optimizing the technique of focused ultrasound ablation to improve long-term efficacy and minimize the risk of side effects.

Keywords: Ablation; Essential tremor; Focused ultrasound; Pallidotomy; Parkinson’s disease; Thalamotomy.

Fig. 1.

Historical ultrasound transducer utilizing open craniotomy. (Journal Of Neurosurgery, January, 1959, 16, 1, Early Experiences With Ultrasonic Irradiation Of The Pallidofugal And Nigral Complexes In Hyperkinetic And Hypertonic Disorders, Meyers, 32–54. An Open Access or Creative Commons publishing model conveys no rights to use this material in any format without written permission from the JNS Publishing Group.)

Fig. 2.

Deterministic tractography to target the ventral intermediate nucleus (in green) for FUSA (lesion outlined in orange). The adjacent white matter tracts, including the internal capsule (red) and the medial lemniscus (blue), are shown.

Fig. 3.

Thermal neuromodulation in FUSA. During the ablation phase, the thermal spot comprises 3 distinct regions. The central core with ablated tissue (thermal dose ≥200 cumulative equivalent minutes [CEM]) is surrounded by a ring of partially ablated tissue receiving a thermal dose between 25 and 200 CEM. The thermal exposure of the outmost ring of tissue reaches the threshold for thermal neuromodulation. (From Sammartino et al. “Thermal Neuromodulation With Focused Ultrasound: Implications for the Technique of Subthreshold Testing”. Neurosurgery. Sep 15 2021;89(4):610–616.)

Fig. 4.

Analyzing lesion characteristics associated with tremor relief (green) and unwanted adverse effects such as ataxia (red) relative to the ventral intermediate nucleus. (Sammartino et al. “Intraoperative lesion characterization after focused ultrasound thalamotomy” J Neurosurg. Dec 31 2021:1–9. An Open Access or Creative Commons publishing model conveys no rights to use this material in any format without written permission from the JNS Publishing Group.)

Fig. 5.

“Hot spot” location for highest therapeutic effect after FUSA, the posterior parcel of GPi. Two distinct locations were found to be associated with the improvement in motor fluctuations (blue) and dyskinesias (red). (Sammartino et al. “Intraoperative lesion characterization after focused ultrasound thalamotomy” J Neurosurg. Dec 31 2021:1–9. An Open Access or Creative Commons publishing model conveys no rights to use this material in any format without written permission from the JNS Publishing Group.)