A Scoping Review of Focused Ultrasound- Blood-Brain Barrier Opening for Treatment of Chronic Pain

Neurosurgery 98:328–338, 2026

This scoping review evaluates focused ultrasound–mediated blood–brain barrier opening (FUS‑BBBO) as a targeted drug‑delivery strategy to treat chronic pain, summarizing systematic literature screening and preclinical evidence. It outlines how FUS parameters, microbubbles, and regional targeting can transiently permit delivery of drugs and particles otherwise excluded by the BBB, potentially improving efficacy and reducing systemic toxicity.

The document surveys candidate therapeutics (opioids, peptides, antibodies, gene therapies) and particle vehicles (nanoparticles, liposomes, niosomes, AAVs), highlights preclinical successes and delivery challenges, and stresses safety, parameter optimization, and the need for human trials. It concludes that FUS‑BBBO combined with advanced delivery platforms holds promise but requires systematic clinical evaluation.

Blood-brain barrier (BBB) challenge: The BBB restricts most drugs from entering the brain, impeding effective pharmacological treatment of chronic pain, with only small, lipophilic molecules (<400–500 Da) able to cross easily, while 98% of small molecules and nearly all large molecules are excluded.

Focused ultrasound (FUS)-mediated BBB opening (FUSBO): FUSBO uses low-intensity ultrasound and microbubbles to temporarily, noninvasively open the BBB, enabling targeted drug delivery to specific brain regions without thermal damage.

Current pain therapies’ limitations: Opioids, gabapentin, cannabinoids, and other agents have limited efficacy and significant systemic side effects due to poor BBB penetration and susceptibility to efflux mechanisms like p-glycoprotein pumps.

Preclinical evidence, lack of human trials: While FUSBO has shown success in animal models for delivering pain therapies directly to the CNS and enhancing efficacy, no human studies have yet assessed FUSBO for chronic pain treatment.

Advancements in drug delivery particles: Nanoparticles, niosomes, polymeric nanoparticles, gold nanoparticles, and liposomes can be engineered to carry drugs across the BBB, improve bioavailability, and reduce toxicity, especially when combined with FUSBO.

Potential for biologics and gene therapy: FUSBO may enable delivery of monoclonal antibodies, single-chain fragment variable antibodies, and adeno-associated virus (AAV) gene therapies to the CNS, overcoming size and immune barriers.

Safety and technical considerations: FUSBO is generally safe in animal and early human studies, but potential risks include microglial activation, microhemorrhage, and neuronal suppression at high intensities; optimal parameters for various drugs and delivery systems remain to be established.

Outlook and clinical promise: FUSBO combined with advanced drug delivery particles could transform chronic pain management by bypassing the BBB, expanding the range of usable therapies, and improving the therapeutic window, but clinical trials are needed to confirm efficacy and safety in humans.