What is the role of brain abnormalities in the pathophysiology of Alzheimer disease (AD) in Down syndrome (DS)?

Updated: Nov 13, 2019
  • Author: Norberto Alvarez, MD; Chief Editor: Jasvinder Chawla, MD, MBA  more...
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Several studies have shown anatomic and chemical differences between the brains of persons with DS and the brains of persons without DS. [46, 43] Postmortem examinations showed indications of growth retardation in the brains of persons with DS. Among other differences, the brains of persons with DS showed lower weight, reduced number and depth of cerebral sulci, narrowness of the superior temporal gyrus, and a smaller cerebellum and frontal and temporal lobes. [47]

Microscopic studies have shown the presence of developmental abnormalities, such as reduced dendritic arborizations and abnormalities in the size and orientation of spines in pyramidal neurons. These abnormalities have been seen in infancy and even in fetal life. [11, 48] These early changes might contribute to the early onset of AD in persons with DS. In that sense, AD in persons with DS is not a perfect model for the understanding of AD in persons without DS.

Several genes in chromosome 21 play an important role in the neurodevelopment of the brain and may be responsible for the abnormalities observed in DS. However, how these changes result in AD in DS is not clear at the present time.

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