Pseudodementia is a phenotype approximated by a wide variety of underlying disorders (1). Data indicate that some of the disorders that can convert to a pseudodementia-like presentation include depression (mood), schizophrenia, mania, dissociative disorders, Ganser syndrome, conversion reaction, and psychoactive drugs (2). Although the frequency distribution of disorders presenting as pseudodementia remains unclear, what is clear is that depressive pseudodementia, synonymously referred to as depressive dementia(3) or major depression with depressive dementia (4), represents a major subclass of the overarching category of pseudodementia (4). It has long been observed that in the differential diagnosis between dementia and pseudodementia, depressive pseudodementia appears to be the single most difficult disorder to distinguish from nosologically established "organic" categories of dementia(5), especially degenerative dementia of the Alzheimer type (6). Depressive Pseudodementia is a syndrome seen in older people in which they exhibit symptoms consistent with dementia but the cause is actually depression.
Older people with predominant cognitive symptoms such as loss of memory, and vagueness, as well as prominent slowing of movement and reduced or slowed speech, were sometimes misdiagnosed as having dementia when further investigation showed they were suffering from a major depressive episode. This was an important distinction as the former was untreatable and progressive and the latter treatable with antidepressant therapy or electroconvulsive therapy or both.
History and controversy of term
The term was first coined in 1961 by psychiatrist Leslie Kiloh, who noticed patients with cognitive symptoms consistent with dementia who improved with treatment. His term was mainly descriptive. The clinical phenomenon, however, was well-known since the late 19th century.
Doubts about the classification and features of the syndrome, and the misleading nature of the name, led to proposals that the term be dropped. However, proponents argue that although it is not a defined singular concept with a precise set of symptoms, it is a practical and useful term which has held up well in clinical practice, and also highlights those who may have a treatable condition.
Presentation and differential
The history of disturbance in pseudodementia is often short and abrupt onset, while dementia is more often insidious. Clinically, people with pseudodementia differ from those with true dementia when their memory is tested. They will often answer that they don't know the answer to a question, and their attention and concentration are often intact, and they may appear upset or distressed. Those with true dementia will often give wrong answers, have poor attention and concentration, and appear indifferent or unconcerned.
Investigations such as SPECT imaging of the brain show reduced blood flow in areas of the brain in people with Alzheimer's disease, compared with a more normal blood flow in those with pseudodementia.
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