Differentials
Depression
SIGNS / SYMPTOMS
Depression is a risk factor for cognitive decline.
Severe depression can sometimes be mistaken for dementia. However, much more commonly depression is seen as a feature in patients with established dementia.
INVESTIGATIONS
Cognitive tests and depression rating scales identify symptoms of depression.
Brain MRI: lack of vascular lesions is supportive.
Alzheimer disease (AD)
SIGNS / SYMPTOMS
Onset of mild cognitive symptoms before stroke onset (stroke can convert those with subclinical AD), lack of clear interval events, gradual course, and rapid forgetting. In many cases, patients probably have a mixed dementia, a combination of AD and vascular disease.
INVESTIGATIONS
Cognitive testing, brain MRI, PET scan. The lack of vascular lesions on brain MRI supports mainly AD. PET scan shows parietotemporal hypometabolism and patchy vascular change.
Mild cognitive impairment (MCI)
SIGNS / SYMPTOMS
State of mild memory decline without loss of social or occupational functioning.
INVESTIGATIONS
Cognitive screening can identify mild memory complaints. Cognitive impairment meets the DSM-5-TR criteria for mild neurocognitive disorder.
Lewy body dementia
SIGNS / SYMPTOMS
Vivid visual hallucinations, autonomic instability, and Parkinson features (shuffling gait, bradykinesia, and falls) are characteristic.
Rapid eye movement sleep disorder may be present.
INVESTIGATIONS
No reliable or valid differentiating test.
Brain pathology demonstrates the presence of round, eosinophilic, intraneuronal inclusions called Lewy bodies. Neuropathologic findings include neurofibrillary tangles, amyloid plaques, and Lewy neuritis.
Frontotemporal dementia
SIGNS / SYMPTOMS
Behavioral variant: impulsive, socially inappropriate behavior; marked apathy or inertia; loss of empathy; hyperorality; marked executive dysfunction. Personality change and behavioral disturbance occur early and are prominent features. Language variants may be progressive nonfluent aphasia, semantic dementia (word meaning), or logopenic (impaired word finding and difficulty with repetition). Onset often at the ages of 50 to 60 years.
INVESTIGATIONS
Brain MRI reveals structural atrophy in the frontal and/or temporal lobes. Positron emission tomography or single-photon emission CT scanning shows reduced brain activity in the frontal and temporal lobes. Brain histology may reveal diagnostic findings (such as Pick bodies composed of tau protein, TDP-43 proteinopathy, or FUS proteinopathy).
Normal pressure hydrocephalus
SIGNS / SYMPTOMS
Gait disturbance and incontinence may be present as well as dementia.
INVESTIGATIONS
MRI shows large nonobstructive dilated ventricles without brain atrophy or vascular lesions.
Primary brain tumor
SIGNS / SYMPTOMS
The cognitive manifestations of a brain tumor depend on its location.
Tumors in the frontal lobes may present with decreased attention and alertness, executive dysfunction, and impaired social judgment.
Tumors in the temporal lobes may present with nonfluent aphasia and memory disorder.
INVESTIGATIONS
Brain imaging will show tumor, and may also show a penumbra of edema and compression of adjacent brain structures.
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