Pathophysiology of Dementia

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). Dementia of Alzheimer’s type 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.  Dementia of Alzheimer’s type believed to have multiple causative factors.



1. Genetic Factors:

• 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 mutation of the amyloid beta-peptide in plaques.
• A specific cholesterol-bearing protein, apolipoprotein E4 (Apoe4), is found on chromosome 19 twice as often as people with DAT as in general population.

2. Biochemical and brain structure factors:

• The neurotransmitter acetylcholine has been implicated in terms of relative deficit and/or receptor abnormalities as related to Alzheimer’s disease.
• Autopsy findings reveal presence of brain changes, that is, the presence of amyloid plaques and neurofibrillary.
• Additional areas of investigation includes: slow viral infection, autoimmune processes, and head trauma.

Secondary Dementia
Occur as a result of another pathologic process.
1. Infection-related dementias

• Acquired immunodeficiency syndrome
• Chronic meningitis
• Creutzfeldt-Jakob disease
• Progressive multifocal leukoencephalopathy
• Postencephalitic dementia syndrome
• Syphilis
• Subacute sclerosing panencephalitis
  Tuberculosis

2. Subcortical degenerative disorders

• Huntington’s disease
• Parkinson’s disease
• Wilson’s disease
• Thalamic dementia

3. Hydrocephalus
4. Vascular dementias
5. Traumatic conditions, such as post traumatic encephalopathy and subdural hematoma.
6. Neoplastic dementias

• Glioma
• Meningioma
• Meningeal carcinomatosis
• Metastatic deposits

7. Inflammatory conditions, such as sarcoidosis, systemic lupus erythematous, and temporal arteritis.
8. Toxic conditions, such as alcohol-related syndrome and iatrogenic dementias
9. Metabolic disorders

• Anemia’s
• Deficiency states
• Cardiac or pulmonary failure
• Hepatic encephalopathy
• Porphyria
• Uremia