Mayo Clinic Research Suggests Patterns of Brain Tissue Loss in Early Alzheimer's Disease May Predict Course of Disease
May 1, 2007 - 9:34:43 AM
Magnetic resonance imaging (MRI) that shows patterns of brain tissue loss may help physicians predict which patients with amnestic mild cognitive impairment (early Alzheimer's disease) will develop full-blown Alzheimer's, according to findings of a Mayo Clinic study presented in Boston today at the annual meeting of the American Academy of Neurology.
By comparing patterns of brain tissue loss in 89 patients with amnestic mild cognitive impairment symptoms, Mayo Clinic researchers found that the 52 patients who developed Alzheimer's lost more tissue in areas of the brain involved in thinking, planning and remembering than did the 37 patients who remained stable and did not progress to Alzheimer's. Amnestic mild cognitive impairment is a transition stage between the cognitive changes of normal aging, specifically memory loss, and the more serious problems caused by Alzheimer's disease.
In the future, these findings may improve physicians' ability to predict the course of the disease and may help identify mechanisms that drive the progression of Alzheimer's -- or protect against it.
"The regions of tissue loss in the brain that the patients with Alzheimer's disease experienced fit the known anatomic progression pattern of Alzheimer's disease," explains Clifford Jack, M.D., the senior author on the study. "But the lack of grey matter tissue loss in the clinically stable patients (patients who didn't progress to full-blown Alzheimer's disease) was unexpected. Why there are these differing patterns of brain atrophy between the two groups is not known, and is a topic of ongoing research."
"Grey matter" refers to brain tissue made up of nerve cell bodies -- the kinds of cells that are destroyed by Alzheimer's disease. Jennifer Whitwell, Ph.D., the study's lead author who presented the findings, says "The fact that there is this difference in tissue atrophy and it is clearly visible on MRI suggests the differential patterns of brain atrophy may be clinically useful in predicting the likely course of Alzheimer's disease. It also may help patients and families prepare for a specific kind of future. This ability alone would be an advance, because one of the most devastating things about Alzheimer's disease is the loss of control and the inability to plan."
Significance of the Mayo Clinic Study
Using MRI images to identify which cognitively impaired patients are likely to progress to Alzheimer's disease and which are likely to remain stable would be an important advance in terms of characterizing the disease and its likely clinical course. Physicians have no way of doing this now. Use of MRI imaging for this identification is still experimental and is not yet available for patient care.
About the Study
In the study, 89 patients who had mild cognitive impairment that included amnesia were given an initial MRI scan and monitored by physicians for 3.5 to 4.5 years. During this time they had clinical exams and additional MRIs to document changes in brain tissue, behavior and cognitive abilities. Each test subject was matched to a healthy person of the same age and gender so physicians could compare changes in the early Alzheimer's disease group two ways: with each other and with a healthy person.
Compared to the control group:
-- patients who developed Alzheimer's disease showed a pattern of loss on both sides of the brain affecting the mesial and inferior temporal lobes, and to a lesser extent, the temporoparietal association neocortex and frontal lobes.
-- stable patients who did not progress to Alzheimer's disease showed no regions of grey matter loss compared to normal elderly control subjects.
Compared to each other, patients who developed Alzheimer's disease showed greater loss in the mesial and inferior temporal lobes, the temporoparietal association neocortex, posterior cingulate and frontal lobes than the stable patients who did not progress to Alzheimer's disease.
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