What is the role of CT scanning in the diagnosis of Alzheimer disease?

Updated: Apr 12, 2018
  • Author: Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS; Chief Editor: L Gill Naul, MD  more...
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The initial criteria for CT scan diagnosis of Alzheimer disease includes diffuse cerebral atrophy with enlargement of the cortical sulci and increased size of the ventricles. A multitude of studies have indicated that cerebral atrophy is significantly greater in patients with Alzheimer disease than in patients who are aging without Alzheimer disease.

This concept was soon challenged, however, because cerebral atrophy can be present in elderly and healthy persons, and some patients with dementia may have no cerebral atrophy, at least in the early stages. The extent of cerebral atrophy was determined by using linear measurements—in particular, bifrontal and bicaudate diameters and the diameters of the third and lateral ventricles. Various measurements were adjusted according to the diameter of the skull to account for normal variation.

To complement this modification, volumetric studies of the ventricles were done. Despite these efforts, it is still difficult to distinguish between findings in a healthy elderly patient and those in a patient with dementia.

In addition, a review of serial CT scans obtained over several months was not clinically useful in the primary diagnosis of the disease.

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