Chapter 58 Alzheimer’s disease
Dementia can be defined as an acquired global impairment of cognitive function (i.e. the intellectual abilities involved in thinking, learning and remembering) with no decrease in the level of consciousness. There are many causes (Table 3.58.1), but by far the most common in industrialized countries is the topic of this chapter, Alzheimer’s disease.
|Primary neurodegenerative disorders||Alzheimer’s disease; Pick’s disease; Huntington’s disease; diffuse Lewy body disease|
|Cerebrovascular disease||Multi-infarct dementia|
|Prion diseases (spongiform encephalopathies)||Creutzfeld–Jacob disease; variant Creutzfeld–Jacob disease|
|Gross structural abnormalities||Hydrocephalus; space-occupying lesions|
|Metabolic abnormalities||Hypothyroidism; liver failure|
|Repeated diffuse trauma||Dementia pugilistica|
|Toxins||Chronic alcoholism; lead poisoning|
|Demyelinating diseases||Multiple sclerosis|
|Vitamin deficiencies||B1, B2, B12|
The changes of Alzheimer’s disease are found mainly in the cerebral cortex and limbic system. The feature most characteristic on macroscopic examination is atrophy of the cortex, most marked in the frontal and temporal lobes. The weight of the brain is reduced and there is compensatory dilatation of the ventricles. The amount of CSF increases to fill the extra space within the skull resulting from the decrease in the amount of brain tissue; this reactive increase in CSF is called secondary hydrocephalus, but note that CSF pressure remains normal.