Health Questions and Answers

Dementia

Define dementia.
Dementia is a progressive decline in cognitive and intellectual functions in the presence of a clear sensorium. Dementia implies that the person has lost intellectual function from a baseline state-i.e., he or she was not born mentally retarded (the process is acquired) and is not delirious, lethargic, or otherwise suffering from an impaired level of consciousness.

List the major causes of dementia along with their incidence.

  • Senile dementia of Alzheimer’s type (50-60%)
  • Multi-infarct dementia (MID) (10-20%)
  • Combination Alzheimer’s and MID (10-20%)
  • Other disorders (5-10%)
  • Reversible or partially reversible causes (20-30%)

What are the other possible causes of dementia?
Other causes of dementia include neurosyphilis, hypothyroidism, HIV infection, neoplasm, subdural hematoma, and head trauma. The old belief that generalized atherosclerosis and global reduction in blood flow can cause dementia has proved correct in only rare cases.
Cerebrovascular disease essentially does not cause dementia except by actual destruction (infarction) of brain tissue, as in MID.

Summarize the general approach to the patient with dementia.
Most dementias, such as Alzheimer’s disease, have no effective treatment, so the evaluation of any patient presenting with dementia generally focuses on finding the treatable causes, even though these are uncommon.

List the reversible causes of dementia.
The reversible causes can be remembered with the aid of the mnemonic DEMENTIA:

D- Drugs
E- Emotional disorders (pseudodementia or depression)
M- Metabolic and endocrine disorders (hepatic encephalopathy, hypothyroidism, chronic renal failure)
E- Eye and ear dysfunction
N- Nutritional deficiencies, normal pressure hydrocephalus (NPH)
T- Tumor, trauma (including chronic subdural hematoma)
I- Infections (neurosyphilis, chronic meningitis)
A- Alcohol, arterosclerotic complications

After the history and physical exam, what tests are used to screen for reversible diagnosis?
A work-up includes CT scan or MRI to image the brain, an electroencephalogram (EEG) to show metabolic encephalopathies (diffuse slowing) or some specific dementias (e.g., periodic sharp waves seen in Creutzfeldt-Jakob disease), and sometimes lumbar puncture to rule out neurosyphilis, cryptococcal meningitis, or other chronic infections. CSF analysis may reveal normal pressure hydrocephalus. Blood studies detect most other causes of dementia, such as hypothyroidism, vitamin B12 deficiency, and vasculitis.

What is Alzheimer’s disease?
Alzheimer’s disease is a degenerative dementing process of unknown etiology. Most elderly patients who were once termed “senile” probably had Alzheimer’s disease, which is now thought to be a specific, distinct disease entity rather than the mere loss of intellectual function with normal aging. Pathologically, Alzheimer’s disease is characterized by degenerative changes in the brain, especially senile plaques, neurofibrillary tangles, and granulovacuolar degeneration.

How is Alzheimer’s disease diagnosed?
There is no biologic marker or specific test for Alzheimer’s disease. The clinical diagnosis is largely one of exclusion. Clinical criteria for the diagnosis of Alzheimer’s disease include:

  • Proof of dementia by neuropsychological testing
  • Deficits in two or more areas of cognition (i.e., not just memory loss)
  • Progressive worsening
  • No disturbance of consciousness
  • Onset between ages 40 and 90 (usually after age 65)
  • Absence of other causes of dementia

Is there any treatment for Alzheimer’s disease?
Because levels of the neurotransmitter acetylcholine are low in Alzheimer’s disease, treatment aims to increase concentrations by inhibiting cholinesterase. The drugs donepezil and rivastigmine are among the most commonly used. Memantine, an NMDA receptor antagonist, may also have some modest benefits. However, no treatment alters the underlying degenerative process.

References
WEB SITES
www.neuroguide.com
www.aan.com (American Academy of Neurology)
www.medmatrix.org
www.internets.com/mednets/sneurolo.htm
www.medwebplus.com/subject/Neurology.html

BIBLIOGRAPHY

  1. Small GW, et al: Diagnoses and treatment of Alzheimer’s disease and related disorders. JAMA 278:1363-1371, 1997.
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