Dementias

Dementia is defined as "impairment in short- and long-term memory, associated with impairment in abstract thinking and judgment, other disturbances of higher cortical function, and personality changes. The disturbance is severe enough to interfere significantly with work or usual social activities or relationships with others." The diagnosis of dementia is not made if these symptoms occur in patients with altered levels of consciousness (Diagnostic and Statistical Manual of Mental Disorders, 4th edition, DSM-IV). Dementia is a prominent feature of a number of neurologic, general medical, and psychiatric diseases. It is imperative to identify the treatable and reversible etiologies of dementia before considering a primary neurodegenerative process as the underlying cause (Table 5.1).

Degenerative dementias are a heterogeneous group. Two major forms are dementias caused by diffuse cortical degeneration and dementias caused by lobar (circumscribed) cortical degeneration. The former form encompasses Alzheimer's disease and dementia with Lewy bodies, and the latter form characterizes the fron-totemporal lobar dementias. Diagnosing the various subforms of dementias can be challenging because definitive diagnosis requires neuropathologic verification. A demonstration of the presence of specific neuronal and glial inclusions is most valuable in confirming the diagnosis and in differentiating between various subforms and eliminating other degenerative diseases of cognitive decline.

TABLE 5.1.

Etiologies of Dementias

Specific causes

Cerebrovascular diseases Normal pressure hydrocephalus Endocrine/metabolic diseases Toxic disorders Head injury Infectious diseases Mass lesion

Hereditary neurometabolic diseases Prion diseases Psychiatric disorders

Neurodegenerative diseases

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