Which findings on neuroimaging are characteristic 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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Answer

There have been several studies of neuroimaging findings in Alzheimer disease. Van de Pol et al found that medial temporal lobe atrophy seems to be a more important predictor of cognition than small-vessel disease in MCI. Lacunes were associated with performance on the Digit Symbol Substitution Test, especially in subjects with milder median temporal lobe atrophy (MTA). There was no discernible association between white matter hyperintensities (WMHs) and the cognitive measures in this study after adjustment for age. [10]

Study of the dopamine transporter (DaTScan) is used to distinguish Lewy body dementia from Alzheimer disease. Numerous studies are under way to identify specific imaging markers for different types of dementia, including cerebral volumetric measurements, diffusion imaging, spectroscopy, very-high-field MRI scans of senile plaques, and PET scan markers of senile plaques. [11]

Neurovascular dysfunction, including blood-brain barrier (BBB) breakdown and cerebral blood flow (CBF) dysregulation and reduction, are increasingly recognized to contribute to Alzheimer disease. [12] BBB impairment is a stable characteristic over 1 year and is present in an important subgroup of patients with Alzheimer disease. Age, gender, ApoE status, vascular risk factors, and baseline Mini-Mental State Examination score did not explain the variability in BBB integrity. BBB impairment as a possible modifier of disease progression is suggested by correlations between the CSF-albumin index and measures of disease progression over 1 year. [13] The BBB is dysfunctional in a portion of all patients with Alzheimer disease, primarily in men. BBB dysfunction may influence the clearance of both harmful and beneficial substances across the barrier. Renal function may have an impact on the BBB. [14]

Pittsburgh Compound-B PET scan findings match histopathologic reports of Aβ distribution in aging and dementia. Noninvasive longitudinal studies to better understand the role of amyloid deposition in the course of neurodegeneration and to determine if Aβ deposition in nondemented subjects is preclinical Alzheimer disease are now feasible. Findings also suggest that AB may influence the development of dementia with Lewy bodies, and therefore, strategies to reduce AV may benefit this condition. [15, 16, 17, 18, 19]


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