Alzheimer's Disease Causes, Stages, and Symptoms (cont.)
Howard Crystal, MD
Melissa Conrad Stöppler, MD
Melissa Conrad Stöppler, MD
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
In this Article
What causes Alzheimer's disease?
The cause(s) of Alzheimer's disease is (are) not known. The "amyloid cascade hypothesis" is the most widely discussed and researched hypothesis about the cause of Alzheimer's disease. The strongest data supporting the amyloid cascade hypothesis comes from the study of early-onset inherited (genetic) Alzheimer's disease. Mutations associated with Alzheimer's disease have been found in about half of the patients with early-onset disease. In all of these patients, the mutation leads to excess production in the brain of a specific form of a small protein fragment called ABeta (Aβ). Many scientists believe that in the majority of sporadic (for example, non-inherited) cases of Alzheimer's disease (these make up the vast majority of all cases of Alzheimer's disease) there is too little removal of this Aβ protein rather than too much production. In any case, much of the research in finding ways to prevent or slow down Alzheimer's disease has focused on ways to decrease the amount of Aβ in the brain.
How Alzheimer's disease diagnosed?
No specific blood test or imaging test exists for the diagnosis of Alzheimer's disease. Alzheimer's disease is diagnosed when: 1) a person has sufficient cognitive decline to meet criteria for dementia; 2) the clinical course is consistent with that of Alzheimer's disease; 3) no other brain diseases or other processes are better explanations for the dementia.
What other conditions should be screened for besides Alzheimer's disease?
Nine other causes of dementia are:
The importance of comprehensive clinical evaluation
Because many other disorders can be confused with Alzheimer's disease, a comprehensive clinical evaluation is essential in arriving at a correct diagnosis. Such an assessment should include at least three major components; 1) a thorough general medical workup, 2) a neurological examination including testing of memory and other functions of thinking , and 3) a psychiatric evaluation to assess mood, anxiety, and clarity of thought.
Such an evaluation takes time - usually at least an hour. In the United States healthcare system, neurologists, psychiatrists, or geriatricians frequently become involved. Nonetheless, any physician may be able to perform a thorough evaluation.
The American Academy of Neurology has published guidelines that include imaging of the brain in the initial evaluation of patients with dementia. These studies are either a noncontrast CT scan or an MRI scan. Other imaging procedures that look at the function of the brain (functional neuroimaging), such as SPECT, PET, and fMRI, may be helpful in specific cases, but generally are not needed. However, in many healthcare systems outside of the United States, brain imaging as not a standard part of the assessment for possible Alzheimer's disease.
Despite many attempts, identification of a blood test to diagnose Alzheimer's disease has remained elusive. Such testing is neither widely available nor recommended.
Medically Reviewed by a Doctor on 9/17/2015
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