Focused ultrasound (FUS) and adjacent emerging modalities represent the next frontier of non-invasive deep brain modulation. MR-guided focused ultrasound (MRgFUS) has FDA approval for tremor-dominant Parkinson's disease and essential tremor (thalamotomy), with active research extending to depression, OCD, addiction, and other psychiatric indications. Low-intensity transcranial focused ultrasound (tFUS) is an emerging research tool for neuromodulation without lesioning. The clinical landscape is evolving rapidly; what is established in 2026 represents a snapshot of a field in active development.
MRgFUS thalamotomy is FDA-approved for movement disorders. The procedure uses focused ultrasound waves to create a small lesion in the ventral intermediate nucleus of the thalamus, treating tremor without skull opening. Procedures are typically outpatient, no incision, real-time MR monitoring of lesion creation. Efficacy in essential tremor and tremor-dominant PD is substantial — comparable to DBS for tremor outcomes, with lower invasiveness. The neuropsychiatric extensions are in active investigation.
OCD applications are emerging. MRgFUS capsulotomy (lesioning the anterior limb of the internal capsule) has been used in severe refractory OCD with promising results in early case series and small trials. The procedure produces durable benefit in selected patients comparable to surgical capsulotomy but with non-invasive delivery. The treatment is reserved for severely refractory cases where standard treatment has been adequately tried and failed; the clinical infrastructure is concentrated in specialty centers.
Depression applications are in earlier stages. FUS targeting of the anterior cingulate cortex and other depression-relevant circuits is in active research; the technique requires substantial development before clinical deployment. The combination of FUS with imaging-targeting allows individualized circuit-based treatment that has appeal for the heterogeneous depression population. The clinical place will be defined over the next several years.
Low-intensity tFUS is a research modality with neuromodulatory rather than lesioning effects. The technology can modulate deep brain structures temporarily without permanent change; the research applications include investigating circuit function and exploring therapeutic neuromodulation. Clinical applications are still emerging; the technology is not yet widely deployed clinically.
Closed-loop neurostimulation represents another frontier. Devices that monitor neural activity and deliver stimulation in response to specific patterns — for epilepsy (NeuroPace RNS), for depression (in research), for OCD (in research) — represent personalization of neurostimulation. The clinical experience in epilepsy demonstrates feasibility and benefit; psychiatric applications are following. The discipline is to remain current with the rapidly developing field, refer to specialty centers when established applications are appropriate, and engage research opportunities for patients whose clinical picture fits emerging applications. The frontier moves quickly; the patient who is severely treatment-resistant in 2026 may have meaningful options that were not available three years prior.