Sunday, October 20, 2013

Biomarkers to detect Alzheimer's disease before the symptoms start

Alzheimer's disease is a devastating decline of brain function, thought to be driven by the accumulation of protein debris in so-called amyloid plaques, loss of neuronal connectivity, and finally death of neurons. It seems likely that these changes begin a decade or more before the disease is first suspected.  It's a major goal of Alzheimer's research to detect the disease as early as possible, before irreversible damage to the brain has occured.
recent study from Johns Hopkins has suggested that a test for two Alzheimer's-related proteins in the cerebral-spinal fluid (CSF) may give clues that something is amiss in brain chemistry as much as 5 years before the cognitive symptoms are seen.
The new work builds on earlier observations that the CSF of patients with advanced Alzheimer's shows abnormal levels of two proteins, phosphorylated tau and beta-amyloid. These proteins are both found near sites of brain damage, so it made sense that they would be detectable in the brain fluid of these advanced patients. The new feature of the Johns Hopkins study is that these same proteins, or at least their ratios, are present in the CSF before the study population had developed symptoms of cognitive decline.
Amyloid plaques, seen here as fuzzy black blotches, in 
the brain of a person who died of Alzheimer's disease.
One of the aspects of Alzheimer's disease that was new to me  is the concept of Cognitive Reserve, that is, that some people can withstand the neuropathology similar to Alzheimer's while not showing cognitive symptoms. It is thought that the psychological flexibility or other life-long habits may improve cognitive resilience during the progression of the disease. This phenomenon makes the diagnosis of Alzheimer's disease more difficult, because each person would have a cognitive decline relative to their own baseline.  The Johns Hopkins group has seen that cognitive reserve does not associate with the proteins they measure in the CSF. Thus this approach may help reduce the uncertainty of diagnosis in patients with more advanced disease, as well as its stated goal of early detection.

1 comment:

David Tal said...

This article is really what I'm looking for it has full of information about early detection of Alzheimer disease. Thanks for sharing this.

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