Researchers at the University of Southern California have developed the first noninvasive method to capture the rhythmic pulsing of the brain's tiniest blood vessels. Using advanced 7T MRI, they found these pulses strengthen with age and hypertension, potentially disrupting waste clearance and contributing to Alzheimer's disease. The findings, published in Nature Cardiovascular Research, could lead to new biomarkers for neurodegenerative conditions.
Scientists at the Mark and Mary Stevens Neuroimaging and Informatics Institute at USC's Keck School of Medicine have pioneered a brain imaging technique that reveals how microscopic blood vessels pulse with each heartbeat. This method measures "microvascular volumetric pulsatility," the subtle swelling and shrinking of these vessels, using ultra-high field 7T magnetic resonance imaging combined with vascular space occupancy (VASO) and arterial spin labeling (ASL) techniques. Previously, observing such changes required invasive procedures limited to animal studies.
The study, published in Nature Cardiovascular Research, shows that these pulses intensify with age, particularly in the brain's deep white matter—a region crucial for inter-network communication but vulnerable to reduced blood flow. Older adults exhibited stronger microvascular pulsations compared to younger individuals, with hypertension exacerbating the effect. "Arterial pulsation is like the brain's natural pump, helping to move fluids and clear waste," said Danny JJ Wang, PhD, professor of neurology and radiology and senior author. "Our new method allows us to see, for the first time in people, how the volumes of those tiny blood vessels change with aging and vascular risk factors."
These amplified pulses may interfere with the glymphatic system, which removes waste like beta-amyloid protein associated with Alzheimer's. "These findings provide a missing link between what we see in large vessel imaging and the microvascular damage we observe in aging and Alzheimer's disease," said lead author Fanhua Guo, PhD. The research connects large artery stiffness—known to raise risks for stroke and dementia—to small vessel changes.
"Being able to measure these tiny vascular pulses in vivo is a critical step forward," noted Arthur W. Toga, PhD, director of the Stevens INI. The team, including Fanhua Guo, Chenyang Zhao, Qinyang Shou, Kay Jann, Xingfeng Shao, and Ning Jin, received support from multiple NIH grants. Future work aims to adapt the method for 3T MRI scanners and test its potential as a biomarker for early Alzheimer's intervention. "This is just the beginning," Wang added. "Our goal is to bring this from research labs into clinical practice."