Alzheimer's disease, a neurodegenerative disorder, has long been associated with the deterioration of gray matter in the brain. However, recent research from the Neuroimaging of Aging and Neurodegenerative Diseases group at the Sant Pau Research Institute challenges this traditional view. The study, published in Alzheimer’s & Dementia, introduces a novel MRI metric called PSMD, which detects early white matter damage in Alzheimer's patients, including those with Down syndrome.
The findings reveal that PSMD identifies white matter abnormalities even before they become visible on conventional MRI scans. This is particularly significant in the context of Down syndrome, where these changes are observed around age 38, approximately 15 years before Alzheimer's dementia typically becomes clinically apparent. The study's lead author, Dr. Alejandra Morcillo-Nieto, emphasizes the importance of this discovery, stating that it supports the idea that Alzheimer's disease affects white matter early in its progression.
One of the key advantages of PSMD is its ability to provide an overall measurement of white matter integrity, making it a valuable tool for research and clinical practice. Dr. Morcillo-Nieto explains that PSMD focuses on white matter tracts and offers a comprehensive view of each individual's brain health. This overall measurement facilitates its interpretation and potential integration as a complementary marker in clinical studies.
The study also highlights the relationship between PSMD and various cerebrospinal fluid biomarkers, such as neurofilament light chain (NfL), which is released when axonal damage occurs. This association supports the idea that PSMD captures relevant structural abnormalities in white matter tracts, primarily composed of myelinated axons. Additionally, PSMD was linked to established Alzheimer's disease biomarkers, including beta-amyloid and tau, as well as markers of glial activation and inflammation.
Dr. Morcillo-Nieto and Dr. Alexandre Bejanin, the head of the research group, believe that PSMD's ability to detect microstructural abnormalities before they become visible on conventional MRI makes it a promising tool for monitoring high-risk populations. They argue that in the context of emerging Alzheimer's treatments, it is crucial to have tools that can monitor not only the established hallmarks of the disease but also the overall condition of brain tissue. PSMD, being derived from diffusion imaging, can provide valuable information about white matter integrity and its changes over time.
The study's findings emphasize the complexity of Alzheimer's disease, suggesting that white matter damage is not solely due to neurodegenerative processes but also involves vascular and inflammatory factors. Dr. Bejanin concludes that a comprehensive understanding of Alzheimer's progression requires incorporating tools that study not only established disease pathology but also vascular, axonal, and white matter damage. This research opens the door to future longitudinal studies, particularly in high-risk populations like those with Down syndrome, to determine whether changes in PSMD predict clinical progression or the development of dementia.
