A new study lead by a team of researchers at the Keck School of Medicine of USC has shown that younger brain age — a neuroimaging-based assessment of brain health — is associated with better post-stroke outcomes. The findings could lead to better ways to predict post-stroke outcomes and offer insight on new potential treatment targets to improve recovery.

Understanding why some stroke survivors show better recovery than others despite similar damage to the brain has been a critical goal in stroke research, since it could help researchers develop better stroke rehabilitation therapies. Much research in the past two decades has focused on the specific location of brain damage and how the lesion affects connected networks in the brain.

The study, published in the journal Neurology, takes into consideration global brain health — a new way of analyzing the health of the brain based on its cellular, vascular, and structural integrity. Although global brain health has been widely examined in aging and neurodegenerative diseases such as Alzheimer’s disease, it has not previously been studied in relation to stroke rehabilitation outcomes. Led by Sook-Lei Liew, PhD, of the Keck School of Medicine’s Mark and Mary Stevens Neuroimaging and Informatics Institute (Stevens INI), the researchers focused on a specific measure of brain age, which examines the biology of the nervous system through neuroimaging of the whole brain.

Brain age is a biomarker that predicts chronological age based on structures such as regional thickness, surface area and volumes, and it is calculated using advanced machine learning algorithms that have been widely studied at the Stevens INI. A higher brain age, calculated as the difference between a person’s predicted brain age minus their chronological age, suggests that the brain appears to be older than the person’s chronological age. Higher brain ages have already been associated with Alzheimer’s disease, major depression, traumatic brain injury and more.

“Brain age has not been widely explored in stroke. A lot of stroke research has focused on how damage to the brain results in negative health outcomes, but there has been less research on how the integrity of the remaining brain tissue supports recovery. We expected that younger-appearing brains would be buffered from the effects of the lesion damage and therefore have less impacts on behavior,” said Liew, who is also an associate professor with Stevens INI, the Chan Division of Occupational Science and Occupational Therapy, the Division of Biokinesiology and Physical Therapy and the USC Viterbi School of Engineering.

The research team conducted an observational study using a multi-site data set of 3D brain structural MRIs and clinical measures from ENIGMA Stroke Recovery, a collaborative working group of more than 100 experts worldwide who contribute post-stroke MRI data to create a worldwide network of stroke neuroimaging centers focused on understanding the mechanisms of stroke recovery.

“The health of your overall brain can protect you from the functional consequences of stroke,” Liew said. “The healthier your brain is, the less likely you are to have a stroke and the less likely you are to have poor outcomes if you do have a stroke. There’s so much research on the aging brain right now, and therapeutics are being developed to slow brain aging. This study ties brain aging to stroke outcomes, so any therapeutics developed to slow brain aging might also be helpful to improve outcomes after stroke.”

Liew and her team plan to apply their brain age assessment method to routine MRI data to determine if it can be an easily implemented biomarker for stroke rehabilitation outcomes. Researchers at Stevens INI collaborate on a variety of stroke research projects, including the Stroke Pre-Clinical Assessment Network (SPAN), which was established to address a significant need in the scientific investigation of stroke treatment. Additionally, Liew and other USC collaborators recently released an expanded, open-source data set of brain scans from stroke patients in hopes of accelerating large-scale stroke recovery research.

For more information, and for a complete list of funding for this research, you can access the paper here.

— Sidney Taiko Sheehan