CMN LIFU for Enhanced Glymphatic Clearance in Amyloid-Positive MCI

This pilot study is a randomized, double-blind, parallel-group trial of repeated low-intensity focused ultrasound (LIFU) stimulation of the centromedian nucleus of the thalamus (CMN) in amyloid-positive older adults with mild cognitive impairment (MCI).

Background and rationale: Poor sleep both predicts and accelerates Alzheimer's disease (AD) pathology, in part by impairing glymphatic clearance of metabolites including soluble amyloid-beta and tau. Slow waves during sleep generate metabolic signals that alter neurovascular tone and cerebrospinal fluid (CSF) volume, creating pulsatile fluid flow thought to support clearance. Slow waves can be entrained by stimulating seed regions of the brain at a slow rate, but existing approaches (transcranial magnetic stimulation, optogenetic or electrical stimulation of the CMN) are too invasive, cumbersome, or costly for regular home use in a broad aging population. Low-Intensity focused ultrasound can both elicit neural activity in the CMN and directly produce fluid flow, non-invasively and with lightweight hardware. In a prior single-session study targeting the CMN in 10 patients with chronic pain, sonication improved subjective sleep for several days. This study extends that preliminary work to a clinical population for which the effects are likely to be therapeutically relevant.

Investigational device: ATTN201 is a head-worn LIFU system that delivers MRI-guided stimulation offline, without real-time imaging or clinician aid. Bilateral 64-element sparse ultrasound arrays operating at 500 kHz are positioned over the temporal windows and deliver cross-beam focused stimulation to deep brain targets. Targeting is participant-specific: before first use, each participant undergoes a 3.0T MRI for personalized targeting. Automated brain segmentation, transducer spatial mapping, and acoustic simulation are used to compute the per-element phase delays required to focus energy at the target. All stimulation remains within International Transcranial Ultrasonic Stimulation Safety and Standards (ITRUSST) consortium recommendations, with sessions lasting up to 60 minutes.

Control condition: Unfocused ultrasound is used as the comparator to maintain participant and study-administrator blinding. It mimics the auditory and peripheral sensations of focused stimulation without creating substantive pressure at the focal target relative to surrounding tissue.

Study conduct: Because the study enrolls people with MCI, capacity to consent is assessed before enrollment using a teach-back method, and only individuals who can demonstrate adequate understanding of the study are enrolled. After screening and informed consent, participants complete screening and baseline visits that include a blood draw for plasma biomarkers, cognitive and functional assessment, safety assessments, and an MRI. Participants then complete at least 5 days of at-home baseline sleep recording using actigraphy, sleep diaries, and wearable EEG. They are subsequently randomized to CMN-focused or unfocused stimulation, delivered during 10 nap opportunities over 2 weeks at the study site or the participant's home, per participant preference. Treatment visits include continuous EEG monitoring, adverse event assessment, and visual analog scales for memory and related psychiatric symptoms; home sleep monitoring continues throughout the treatment period. A post-treatment visit repeats the baseline measures, including cognitive testing, neurological exam, blood draw, and an MRI. An optional follow-up visit 3 months later repeats the same measures to assess durability of effects. The study is conducted in conformance with Good Clinical Practice (GCP).