Summary: A new method of visually assessing shrinkage of certain areas of the brain using standard MRIs may improve the diagnosis and treatment of Alzheimer's.
ICAD was all about biomarkers. Biomarkers are physical or biochemical characteristics that are signs of an ongoing disease process in a living person. They include genetic variations, molecules in blood or spinal fluid, and patterns seen on imaging tests. To be useful in screening for a disease or monitoring the progress of a disease, they should be easy to obtain. This typically involves collecting blood, urine, stool or saliva samples, or performing a radiological test. The use of biomarkers for certain diseases is well-accepted - for example, blood tests are used to indicate the presence of certain cancers or the risk of heart disease.
But for Alzheimer's, diagnosis is currently based on neuropsychological tests and medical histories showing cognitive impairment. Brain scans (MRI and CT scans) are not typically used to diagnose Alzheimer's, but instead are used to exclude other conditions that can cause cognitive problems.
Speaker after speaker at ICAD explained that we need biomarkers to:
- diagnose [and eventually treat] Alzheimer's in early stages, perhaps even before symptoms appear
- diagnose Alzheimer's more accurately, at any stage
- measure the effect of drugs on disease progression in clinical trials.
This concept sounds good, but there are practical problems:
- studies have not yet confirmed the accuracy of many of the biomarkers proposed; a high percentage of false positive results seems possible
- new technologies to measure potential biomarkers like amyloid protein in the brain are expensive and not yet available outside of research facilities
- some studies have shown that the levels of certain proteins in spinal fluid may be an accurate biomarker, but the required spinal tap is unappealing to many patients.
Dr. Ranjan Duara, Medical Director of the Wien Center for Alzheimer's Disease and Memory Disorders in Miami Beach, Florida and Associate Professor of Medicine, Neurology and Psychiatry at the University of Miami, thinks we already have a biomarker that is accurate, inexpensive and doesn't require drawing spinal fluid. He has developed a system for visually measuring and rating the atrophy, or shrinkage, of three areas within the medial temporal lobe of the brain. He and his colleagues recently completed a study showing that this method can help differentiate among people who are cognitively normal, those with Mild Cognitive Impairment and those with Alzheimer's. The study also showed that this assessment can help predict which patients will progress from Mild Cognitive Impairment to Alzheimer's.