Neuroimaging for dementia and alzheimer’s disease

There are an estimated 4.5 million people in the United States with Alzheimer’s disease (AD) at this time, accounting for approximately 60-70% of all cases of dementia in the elderly. How do you test for alzheimer disease As the post World War baby boom population ages, it is anticipated that the number of Alzheimer’s patients will grow dramatically, increasing the burden on both the public healthcare system as well as the caregivers of these patients. Early onset alzheimer’s disease Unfortunately, treatments available at this time for AD are not effective at slowing disease progression. What causes alzheimer’s disease However, for the first time, promising disease-modifying therapies for AD are in large-scale clinical trials and it is likely that some will become available within the next few years.

The only definitive diagnosis of AD is the detection of amyloid plaques and neurofibrillary tangles at autopsy. What are the major symptoms of alzheimer’s disease A clinical diagnosis of based on the history, physical examination, neuropsychological evaluation, and laboratory tests is usually accurate in established cases, but is more challenging in earlier, milder forms of the disease. Medical definition of alzheimer’s disease The role of neuroimaging at present is primarily to identify potentially treatable underlying conditions that arise in patients with unusual presenting symptoms.


What is alzheimer’s disease While AD is by far the most common form of dementia (Table 1), other etiologies must be considered because prognosis and management strategies will differ. Alzheimer’s disease symptoms Neuroimaging is often useful for this purpose, for example, in differentiating vascular and fronto-temporal dementias from AD. What age can you get alzheimer’s disease The role of neuroimaging in the next few years will likely include the direct identification of early amyloid AD pathology with positron emission tomography (PET) and the detailed characterization of brain chemistry with magnetic resonance spectroscopy (MRS).

By the time AD symptoms are clinically established, structural brain shrinkage in excess of normal aging is often evident and readily detectable with either CT or MRI. Cause of alzheimer’s disease AD causes atrophy of the entire brain, although some regions such as the hippocampus are specifically affected by AD and can be assessed with quantitative volumetric methods that are usually applied to MRI (Figure 1). What are the treatment of alzheimer disease Up to 5% of patients presenting for initial evaluation for dementia harbor a clinically significant structural lesion that is not identified by history or examination. Familial alzheimer’s disease Most commonly, these lesions are infarcts but occasionally neuroimaging can reveal a tumor or subdural hematoma requiring surgical evaluation. Alzheimer’s disease treatment options CT is usually adequate as an initial examination to look for these lesions.

Figure 2. Alzheimer’s disease pdf FDG PET images showing patterns of metabolic activity that are characteristic of patients with Alzheimer’s disease, Pick’s disease (fronto-temporal dementia) and elderly individuals with no dementia. About alzheimer’s disease Red, high FDG uptake, Blue, low FDG uptake.

FDG-PET is useful for distinguishing between Alzheimer’s and fronto-temporal (Pick’s) dementias and is now Medicare reimbursable for this purpose. Alzheimer disease test peanut butter Before FDG-PET can be ordered, a scheduling worksheet must be completed that documents the justification for and potential benefit of FDG-PET for clinical management of the patient (Table 2).

FDG-PET images show the regional distribution of the rate of glucose metabolism. Pathophysiology of alzheimer disease pdf Because active neurons have a very high metabolic rate, FDG uptake is high in brains of healthy subjects, especially in the cortex. How early can you get alzheimer’s disease In contrast, FDG uptake in AD is greatly diminished, especially in the temporal and parietal regions of the brain. Signs and symptoms of alzheimer’s disease The characteristic pattern of FDG uptake seen in Alzheimer’s patients is very different from that seen in fronto-temporal dementia (Figure 2), allowing the differential diagnoses of these diseases.

Proton magnetic resonance spectroscopic imaging (MRS) can be performed as an add-on examination after conventional MRI. Alzheimer’s disease test Proton MRS imaging assesses several characteristic hydrogen-containing biochemicals in an array of voxels, each about 2-7 cm 3, which are displayed as a spectrum for each voxel of tissue. Can you die from alzheimer’s disease One of the principle peaks in the spectrum of a healthy brain is that of the neuronal marker, n-acetyl aspartate (NAA), while other major peaks include choline, creatinine, and myo-inositol. What are the causes and symptoms of alzheimer disease Even before the development of overt dementia due to AD, there is a decrease in the ratio of NAA: creatinine in the temporal lobe, which is not seen in patients whose memory loss and cognitive declines were attributed to other causes of dementia.

Several highly specific PET imaging agents have been developed which bind to the characteristic b-amyloid plaque found in AD. Types of alzheimer’s disease Currently, the most sensitive and specific of these, known as Pittsburgh Compound B (PIB), rapidly crosses the blood brain barrier and is retained by ß-amyloid fibrils but not in normal brain tissue. Alzheimer’s disease meaning In Alzheimer’s patients, the high contrast images show marked retention of PIB in areas where ß-amyloid is characteristically found, such as the parietal and frontal cortices. Is there treatment for alzheimer’s disease In contrast, patients with fronto-temporal dementia have normal-appearing PIB images.

Interestingly, PIB binding is seen in approximately 20% of apparently normal older subjects, and whether this is an indication of antecedent AD is a topic of intense investigation. Stages of dementia alzheimer’s disease PIB-PET also has applications in drug development because it can be used to demonstrate whether drugs that are designed to act on ß-amyloid, which are currently in development, reduce or stabilize the burden of ß-amyloid plaque.

At this time, both proton MRS and PIB-PET are research tools. Alzheimer’s disease history However, with the recent dramatic advances in understanding the biology of AD and the expectation that drugs will become available to treat it, these neuroimaging tools will likely be brought into the clinical mainstream for early diagnosis and intervention.

MRI or CT for evaluation of patients with dementia may be ordered through ROE for appointments at the MGH Main Campus, Mass General West Imaging Waltham, and MGH Chelsea Health Center, or by telephone 617-724-XRAY (9729) for all locations.

FDG PET may be ordered by telephone at 617-724-7212 after the completion of a scheduling worksheet documenting the diagnosis evidence for AD and fronto-temporal dementia and the potential benefits of FDG PET imaging.

For further questions, please contact Ramon Gilberto Gonzalez, M.D., Ph.D., Chief of the Division of Neuroradiology, MGH Department of Radiology at 617-726-8628.

We would like to thank Dr. Facts about alzheimer’s disease Gonzalez and Keith Johnson, M.D., Neurologist and Radiologist, Nuclear Medicine Division, MGH Department of Radiology, for their assistance and advice for this issue.

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