Magnetic Resonance-Guided High Intensity Focused Ultrasound for Treating Movement Disorders.

Transcranial magnetic resonance-guided focused ultrasound (MRgFUS) surgery has recently gained favor as a novel, noninvasive alternative to conventional neurosurgery. In contrast to traditional ablative interventions, transcranial MRgFUS surgery is entirely imaging-guided and uses continuous temperature measurements at the target and surrounding tissue taken in real-time. Unlike Gamma Knife radiosurgery, MRgFUS surgery can make a lesion immediately and does not use ionizing radiation. Moreover, since no metallic device is implanted, MR imaging-based diagnosis is not restricted throughout life. An additional strength of transcranial MRgFUS surgery is its ability to focus acoustic energy through the intact skull onto deep-seated targets, while minimizing adjacent tissue damage. Even though the established indications of MRgFUS include bone metastases, uterine fibroids, and breast lesions, several promising preclinical and phase I clinical trials of neuropathic pain, essential tremor, Parkinson's disease (PD), and obsessive-compulsive disorder have demonstrated that the delivery of focused ultrasound energy promises to be a broadly applicable technique. For instance, this technique can be used to generate focal intracranial thermal ablative lesions of brain tumors, or to silence dysfunctional neural circuits and disrupt the blood-brain barrier for targeted drug delivery and the modulation of neural activity. Here we review the general principles of MRgFUS and its current applications, with a special focus on movement disorders such as essential tremor and PD, and discuss controversies and limitations of this technique.