Pathophysiology

Primary Dementia :

  • Primary dementias are degenerative disorders that are progressive, irreversible, and not due to any other condition. Specific disorders are dementia of the Alzheimer’s type (DAT) and vascular dementia (formerly multi-infarct dementia). DAT demonstrates progression of symptoms from the initial stage, which is characterized by mild cognitive deficits in the area of short-term memory and accomplishment of goal-directed activity, to the final stage in which profound impairment occurs in the areas of cognition and self-care abilities. Research is ongoing; however, DAT is believed to have multiple causative factors.
  • Genetic factors:
  1. Familial Alzheimer’s disease is associated with abnormal genes on chromosomes 1, 14, and 21. In particular, with genes located on these chromosomes (1 and 14) that encode for amyloid precursor protein which leads to accumulation of the amyloid beta-peptide in plaques.
  2. A specific cholesterol-bearing protein, apolipoprotein E4 (Apo E4), is found on chromosome 19 twice as often in people with DAT as in the general population.
  • Biochemical and brain structural factors:
  1. The neurotransmitter acetylcholine has been implicated in terms of relative deficit and/or receptor abnormalities as related to Alzheimer’s disease.
  2. Autopsy findings reveal presence of brain changes, that is, the presence of amyloid plaques and neurofibrillary tangles associated with nerve cell destruction.
  3. Additional areas of investigation include:
  • Slow viral infection.
  • Autoimmune processes.
  • Head trauma.

Secondary Dementia:

Occur as a result of another pathologic process.

  • Infection-related dementias
    • Acquired immunodeficiency syndrome
    • Chronic meningitis
    • Creutzfeldt-Jakob disease
    • Progressive multifocal leukoencephalopathy
    • Postencephalitic dementia syndrome
    • Syphilis
    • Subacute sclerosing panencephalitis
    • Tuberculosis
  • Subcortical degenerative disorders
    • Huntington’s disease
    • Parkinson’s disease
    • Wilson’s disease
    • Thalamic dementia
  • Hydrocephalic dementias
  • Vascular dementias
  • Traumatic conditions, such as posttraumatic encephalopathy and subdural hematoma
  • Neoplastic dementias
    • Glioma
    • Meningioma
    • Meningeal carcinomatosis
    • Metastatic deposits
  • Inflammatory conditions, such as sarcoidosis, systemic lupus erythematosus, and temporal arteritis
  • Toxic conditions, such as alcohol-related syndrome and iatrogenic dementias (anticonvulsant, anticholinergic, antihypertensive, psychotropic drugs)
  • Metabolic disorders
    • Anemias
    • Deficiency states (minerals and vitamins)
    • Cardiac or pulmonary failure
    • Hepatic encephalopathy
    • Porphyria (deficiency in enzymes involved in heme synthesis)
    • Uremia