Degenerative Diseases and Dementias

Degenerative Diseases and Dementias

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NOTICE: This article is a pathological discussion on Degenerative Diseases and Dementias.


  • Dementia, defined as the development of memory impairment and other cognitive deficits with preservation of a normal level of consciousness.
  • It is emerging as one of the most important public health issues in the industrialized world.

regardless of etiology, dementia is not part of normal aging and always represents a pathologic process.

Causes of Dementia:

  • Neurodegenerative Disorders
  • Infections
  • Vascular and Traumatic Diseases
  • Metabolic and Nutritional Diseases
  • Miscellaneous


  • Alzheimer disease (AD) is the most common cause of dementia in the elderly.
  • Incidence
  1. 3% for 65 to 74 years old
  2. 19% for 75 to 84 years old
  3. 47% for 85 years or more


  • 1906, German neurologist Alzheimer first reported the disease
  • The incidence of AD increased with increasing age

Clinical features of Alzheimer’s disease:

  • Alterations in mood and behavior
  • Disorientation
  • Memory loss
  • Aphasia (Aphasia indicate severe cortical dysfunction)
  • Profoundly disabled
  • Mute
  • Immobile
  • Death (intercurrent pneumonia or other infections)

Pathogenesis of Alzheimer’s disease:

  • Genetic factors
  • Deposition of a form of amyloid
  • Hyperphosphorylation of the protein tau
  • Expression of specific alleles of apoprotein E (apo E)

Morphology of Alzheimer’s disease:


  • Cortical atrophy

–widening of the cerebral sulci, most pronounced in the frontal, temporal, and parietal lobes.

  • Ventricular enlargement

–secondary to loss of parenchyma

Grossly the brain shows a variable degree of cortical atrophy with widening of the cerebral sulci that is most pronounced in the frontal, temporal, and parietal lobes.

With significant atrophy, there is compensatory ventricular enlargement (hydrocephalus ex vacuo) secondary to loss of parenchyma.

cerebral atrophy

The cerebral atrophy seen here mainly in the frontal and parietal regions is characterized by narrowed gyri and widened sulci.

Microscopic features of Alzheimer’s disease:

  • Neuritic (senile) plaques
  • Neurofibrillary tangles
  • Amyloid angiopathy
  • Granulovacuolar degeneration
  • Hirano bodies

Pathologic changes ( plaques, tangles, and the associated neuronal loss and glial reaction) are evident earliest in the entorhinal cortex, then spread through the hippocampal formation and isocortex, and then extend into the neocortex.

Micrscopic features of Alzheimer's disease

Congo red stain of the cerebral cortex showing amyloid deposition in the blood vessels and the amyloid core of the neuritic plaque (arrow).

Micrscopic features of Alzheimer's disease

Neurofibrillary tangles (arrowheads) are present within the neurons (H & E).

Silver stain showing a neurofibrillary tangle within the neuronal cytoplasm.

The tangle appears as long pink filaments in the cytoplasm. They are composed of cytoskeletal intermediate filaments.

Click here to read about Pathological discussion on another Degenerative Disease (Parkinson’s Disease)

To visit all informative Medical related posts on this website click here or go to the home above.

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