DSM-IV DEFINITION OF DEMENTIA: "... the development of multiple cognitive deficits that include memory impairment and at least one of the following cognitive disturbances: aphasia,apraxia, agnosia, or a disturbance in executive functions. The cognitive impairment must be sufficuently severe to cause impairment in occupational or social functioning and must represent a decline from a previously higher level of functioning."

PREVALENCE: 2-4% of people >65 years old, increasing with age, with 20% in the >80-year-old group

DEMENTIA TYPES AND ASSOCIATED FEATURES: There are a variety of "dementias" which most frequently are categorized as "cortical" or subcortical." Alzheimer’s disease is the most well-known example of a cortical dementia. Subcortical dementias include Parkinson’s, Huntington’s, and AIDS dementia. The presentation of these two types of dementias differ:
 

EMOTIONAL SEQUELAE OF STROKE (CVA): A variety of psychiatric symptoms have been associated with CVA, including:

affective syndromes dementia

apathy syndromes frontal lobe syndrome

anxiety syndromes indifference reaction

aprosody delusional disorders

catastrophic reaction personality change

delirium

LESION LOCATION AND DEPRESSION:

A study by Robinson et al. (1983) of stroke patients (all right-handed, no psychiatric history, and non-aphasic) found depression in 60% of patients with left anterior frontal lesions, compared to 18% of patients with left posterior lesions, 17% right posterior lesions, and 0% of thoses with right anterior frontal lesions.

This left-right hemisphere difference has also been found in subcortical infarctions, with left-sided more likely to result in depression.

CO-OCCURRENCE OF DEPRESSION AND DEMENTIA:

Alzheimer’s disease - Depression likely to occur early in disorder, when patient first becomes aware of decreasing function. As the disorder progresses, insight becomes impaired, such that the patient no longer is aware of their deficits and depression is less likely to occur. Immediate, brief, catastrophic reactions may occur in reaction to negative events, but are not likely to persist.

Subcortical dementias - Depression tends to be part of the total symptom picture, with mood alteration not solely situational and more likely to be persistant. May respond to standard interventions. Depression likely to exacerbate cognitive deficits.

Multi-infarct/vascular dementia - Given correlation between left hemisphere infarcts and depression, as well as the greater frequency of left hemisphere CVAs, depression is very common after stroke, regardless of dementia. In cases of vascular dementia, there typically is a "patchy" presentation of deficits. Often insight is preserved, so that the patient is aware of their impairment. Thus, depression may result from lesion location and/or reaction to new limitations. Depression likely to exacerbate cognitive deficits.

1) intellectual impairment in a patient with a primary psychiatric disorder

2) features of impairment are similar to those seen in CNS disorders

3) the cognitive deficits are reversible

4) there is no known neurological condition to account for the presentation

 
PREVALENCE: Of patients referred for dementia evaluation, reports in the literature have ranged from 2% to 32% found to have a pseudodementia, with most reporting about 10%. There also is suggestion of overdiagnosis of degenerative dementia, with some studies reporting 20-50% of patients being misdiagnosed who really have a pseudodementia. Most cases occur in later life, with few reports in early or midlife.
 

                                                    Relative frequency (%) of illness
 

PSEUDODEMENTIA FEATURES:

• depressed affect/mood
• neurovegetative signs
• slow, aspontaneous, monotonous speech
• long response latency
• frequent "I don’t know" responses
• quick to give up, but persists with encouragement
• disorientation
• impaired attention/distraction
• incomplete responses
• forgetfulness - particular deficits in learning new information, although memory may be patchy
• poor abstraction
• typically make errors of omission, vs. errors of commision
• awareness of cognitive difficulties
• may have concern over deficits - "Do I have Alzheimer’s? See, I can’t remember anything!"
• if psychosis, delusions typically nihilistic, self-deprecatory, paranoid
• no signs of aphasia, apraxia, or agnosia
• greater similarity to subcortical dementias, such as Parkinson’s

    Cummings, J.L. & Benson, D.F. (1992). Dementia: A Clinical Approach. Boston: Butterworth-Heinemann.

Cummings, J.L., Ed. (1990). Subcortical Dementia. New York: Oxford University Press.

LaRue, A. (1992). Aging and Neuropsychological Assessment. New York: Plenum Press.

    Reichman, W.E. & Katz, P. (1996). Psychiatric Care in the Nursing Home. New York: Oxford University Press.

    Yesavage et al. (1983). Development and validation of a geriatric depression screening scale: A preliminary report. Journal of Psychiatric Research, 17, 37-49.