Focused Ultrasound for Treatment of Movement Disorders: A Review of Non-FDA Approved Indications

Introduction: MRI-guided focused ultrasound (FUS) may be used to treat medication-refractory movement disorders, with a growing number of anatomic targets and clinical applications. The only US Food and Drug Administration (FDA)-approved uses of FUS for movement disorders are thalamotomy for essential tremor (ET) and tremor-dominant Parkinson’s Disease (PD), and pallidotomy for other cardinal symptoms of PD. We review all non-FDA approved indications of FUS for movement disorders, beyond the well-described indications of ET and PD.

Methods: A systematic review was conducted on use of FUS for all non-FDA approved movement disorders, excluding thalamotomy for ET and PD, and pallidotomy for PD.

Results: A total of 25 studies on 172 patients were included. For tremor plus dystonia syndromes (n=6), ventralis intermediate nucleus of the thalamus (VIM)-FUS gave >50% tremor reduction, with no improvement in dystonia and worsened dystonia in 2/6 patients. Ventral-oralis complex (VO)-FUS gave >50% improvement for focal hand dystonia (n=6) and 100% return to musical performance in musician’s dystonia (n=6). For multiple sclerosis (MS)-related tremor (n=3), tremor improved in two patients with a favorable skull density ratio; no MS disease change was noted after VIM-FUS. In patients with tremor and comorbid ataxia syndromes (n=3), none were found to have worsened ataxia after VIM-FUS; all had clinically significant tremor improvement. Subthalamic nucleus (STN)-FUS for PD (n=49) gave approximately 50% improvement in PD motor symptoms, with dystonia and mild dyskinesias as possible adverse effects. Cerebellothalamic tract (CTT-FUS) for ET (n=42) gave 55-90% tremor improvement, with gait dysfunction as a rare persistent adverse effect. Pallidothalamic tract (PTT-FUS) for PD (n=50) gave approximately 50% motor symptom improvement, with mild speech dysfunction as a possible adverse effect.

Conclusion : There are several non-FDA approved surgical targets and indications that hold promise for treatment of medication-refractory movement disorders. Larger prospective trials with long-term follow-up evaluating safety and efficacy are warranted.