Transcranial Focused Ultrasound Stimulation for Alzheimer's Disease-A Scoping Review

Background/Objectives: Alzheimer's disease (AD) remains a significant global health challenge, characterised by a persistent resistance to traditional pharmacological interventions. While non-invasive brain stimulation (NIBS) techniques like transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) show therapeutic promise, their limited depth of penetration restricts their efficacy in targeting deep-brain AD pathology. Transcranial focused ultrasound stimulation (tFUS) has emerged as a novel, non-invasive neuromodulatory tool capable of precise deep-brain targeting. This scoping review aims to systematically map the current evidence base regarding the neuromodulatory application of tFUS in AD. Methods: Following PRISMA-ScR guidelines, a scoping search was conducted across four major databases (Ovid MEDLINE, Embase, Web of Science, and CENTRAL). Studies were included if they investigated focused ultrasound stimulation (FUS) as a neuromodulatory intervention for AD, excluding applications involving blood-brain-barrier disruption via microbubbles. Two independent reviewers performed screening and data extraction, with inter-rater reliability assessed via Cohen's kappa. Results: Our analysis indicates that tFUS represents a safe and potent multi-modal intervention for AD that addresses both pathological protein aggregation and electrophysiological network failure. Its ability to modulate neuroplasticity and metabolic recovery suggests a promising therapeutic trajectory. Conclusions: Future research should prioritise the standardisation of acoustic protocols and the pursuit of longitudinal clinical cohorts to establish the long-term efficacy of this non-invasive technology.