Technical Review and Perspectives of Transcranial Focused Ultrasound Brain Stimulation for Neurorehabilitation

ABSTRACT

Lack of a region-specific brain stimulation modality having both spatial specificity and depth penetration has limited clinicians to explore novel non-pharmacological treatment options in neurorehabilitation. Focused ultrasound (FUS) has shown excitatory and suppressive modulatory effects on neural tissues in both central and peripheral nervous systems by transcranially delivering low-intensity highly focused acoustic pressure waves to region-specific neural structures in a completely non-invasive fashion. This emerging technique, with exquisite spatial selectively and depth penetration, is considered as a new mode of brain stimulation that may significantly improve existing brain stimulation modalities. This review aims to provide the perspectives of FUS-mediated brain stimulation in neurorehabilitation, along with potential pitfalls and cautions that need to be taken into consideration. When combined with the intravascular introduction of microbubble-based ultrasound contrast agents, the technique adds therapeutic potentials in delivering drug/genes/cells across the blood-brain barrier, which may open new opportunities for neurorehabilitation. Efforts are being made to construct FUS devices appropriate for routine clinical use, to investigate its fundamental mechanisms, and to optimize the sonication parameters. Repeated administration of the technique for inducing neuroplasticity, including the assessment of long-term safety, is warranted to reveal its utility in neurorehabilitation.