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The dementia differential diagnosis thread

5 posts in this topic

Patients with Alzheimer's disease have early language and visuospatial deficits. The deficits in short-term memory are severe, and clues do not help in retrieving information. The onset of the disease is gradual, with a slow progression. Usually, no motor findings are present until the middle or late stages of the disease.

Patients with vascular dementia have patchy cognitive impairment, often with focal neurologic signs and symptoms. Onset may be abrupt, with a stepwise decline.

Patients with Parkinson's dementia have cognitive slowing with extrapyramidal signs such as rigidity, bradykinesia, tremor, and gait disturbances. Usually, dementia is seen in later stages of the disease.

Patients with dementia due to head trauma have memory impairment, and other cognitive deficits associated with a history of head trauma occur. The physical findings depend on the location of injury. Usually, it is not progressive unless the person has a history of repeated head trauma (eg, dementia pugilistica).

Patients with HIV dementia have cognitive changes with neurologic signs and a positive result from an HIV test.

Patients with Pick disease have memory problems, personality changes, and deterioration of social skills. Onset is usually between the fifth and sixth decades of life. Upon physical examination, the patient has frontal release signs such as snout and grasp reflex.

Huntington disease is an autosomal dominant disease with an onset of cognitive changes as early as the third decade of life, with physical signs of choreoathetosis.

In Creutzfeldt-Jakob disease, onset is between the fourth and sixth decades of life and is associated with signs such as myoclonus, seizures, and ataxia. A rapid progression is typical.

Patients with Lewy body dementia have recurrent visual hallucinations, fluctuating cognitive impairment, and parkinsonism features. Also, the frequency of adverse reactions to antipsychotic medications is high.

In the case of cognitive symptoms secondary to depression, the onset is acute compared with the insidious onset in most types of dementia. The term pseudodementia has been used to describe the condition when cognitive symptoms are prominent. The current and more accurate name for this state is dementia of depression. Patients with depression usually report their cognitive difficulties, which is unusual for patients with dementia. Patients with depression tend to state that they do not know the answers to questions, and they appear to not try very hard during neuropsychological evaluations. Mood symptoms are prominent in patients with dementia of depression.

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Table from Tueth 95

Pseudodementia (PD) vs. Alzheimer’s disease (AD) (Reproduced with permission from [5]).


Characteristic PD AD


Onset Fast Slow

History of depression Positive Negative

First symptoms Depressive Cognitive

Current symptoms Exaggerated Minimized

Response to question I don’t know Tries but fails

Memory Recent/Long-term &nbsp:lol:ecreased Recent decreased

Performance Variably abnormal Consistently abnormal

Night-time behavior Same as day Worse at night

Visuospatial ability Usually preserved Often abnormal

Language Usually preserved Often abnormal

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Vascular vs. Alzheimers dementia

Patients with vascular dementia have patchy cognitive impairment, often with focal neurologic signs and symptoms. Onset may be abrupt, with a stepwise decline.

Frontal lobes affected early with abulia and apathy

Cognitive function:

Patchy deficits

Better recall and fewer recall interruptions than AD

Do worse than AD on frontal lobe / executive function with poorer verbal fluency, more perseverative behavior, cognitive slowing, difficulty in shifting sets, and problems with abstraction

For patients with single or multiple large infarcts, deficits correlate with the site and extent of the infarct

Lateralizing signs such as hemiparesis, bradykinesia, hyperreflexia, extensor plantar reflexes, ataxia, pseudobulbar palsy, and gait and swallowing difficulties may be observed.

Severe depression more common than in AD

Risk factors for vascular dementia include hypertension, smoking, hypercholesterolemia, diabetes mellitus, and cardiovascular and cerebrovascular disease.

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Major characteristics of the dementia syndrome of depression (all characteristics need not be present) (from Cummings and Benson, 1992)


Mental status changes



decreased motivation  


depressed affect

persecutory delusions  

psychomotor retardation  

impaired memory retrieval  

poor wordlist generation

dilapidation of cognition (calculation, abstraction)  

variable performance  

awareness of cognitive deficit

Neurovegetative signs  

sleep disturbance  

loss of appetite and weight  



Motor manifestations


masked facies

stooped posture  

slow, hypophonic speech


subacute onset and rapid progression of intellectual decline  

past history of mood disorder  

family history of mood disorder


positive Dexamethasone test  

enlarged lateral ventricles

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