Dementia is very common, and is the most disabling psychiatric disorder in the adult population. The incidence increases exponentially with age, from 0.5% at age 40 years up to 20% of the population aged 80 years and over. Over 80% of patients with dementia suffer from a small number of conditions, associated with characteristic types of pathology and different etiologies.


% of dementia cases

Alzheimer's disease


Cerebrovascular disease


Cortical Lewy body disease


Head trauma


Parkinson's disease


Motor neuron disease




AIDS dementia (prion disease)




AIDS: acquired immune deficiency syndrome.

AIDS: acquired immune deficiency syndrome.

Frontal predominance atrophy, abnormal intensity of the basal ganglia

White matter and deep gray lacunae, central pontine infarcts and strokes of different ages

E.g., hemiatrophy of one hemisphere

E.g., from trauma, infection, and perinatal ischemia

Differential diagnosis

Degenerative disorders

Presenile dementia

- Alzheimer's disease

- Pick's disease

- Cortical Lewy body disease

- Prion disease

- Huntington's chorea

Senile dementia

Cerebrovascular disease

Multi-infarct dementia A series of relatively large infarcts damaging a sufficient volume of brain results in dementia. Neuro-pathological calculations indicate that infarct volumes that total over 50 mL are often associated with dementia, and that a total infarct volume over 100 mL is always associated with dementia. Vascular dementia may coexist with Alzheimer's disease in 20% of cases, and smaller volumes of infarct could therefore contribute significantly to the dementia symptoms

Cerebral embolism

Cerebral hemorrhage

Subarachnoid hemorrhage

Disseminated lupus ery-thematosus

Transient ischemic attacks

Head injury

Acute head injury

Subdural hematoma Posttraumatic dementia Hypoxia

Post-cardiac arrest

- Heart failure

- Myocardial infarction

Respiratory disorders

Carbon monoxide poisoning

Intracranial tumors



- Encephalitis

- Meningitis

- Meningoencephalitis

- AIDS dementia

General Epilepsy

Toxic disorders


E.g., general paresis

E.g., Urinary tract, bronchopneumonia, topical infection

E.g., Alcohol, barbiturates, opiates, amphetamines, LSD, cocaine, tricyclic antidepressants, steroids, lithium, l-dopa, cycloserine, digoxin, MAOIs, cycloserine, isoniazid

Heavy metals E.g., Lead, mercury, manganese

Metabolic disorders


- Electrolyte disturbance

- Uremia

- Hepatic encephalo-pathy

- Hypoglycemia

- Porphyria

- Endocrine diseases E.g., thyrotoxicosis, diabetes mellitus, Addison's dis ease, parathyroid disorder, hypopituitarism

- Vitamin deficiencies E.g., thiamine, B12, nicotinic acid


- Chronic alcoholic dementia

- Heavy metals

- Myxedema, hypogly-cemia, hypopituitar-ism

- Vitamin deficiency

E.g., thiamine—Korsakoff's psychosis; nicotinic acid-pellagra; vitamin Bi2 and folic acid

Other disorders affecting the CNS

Multiple sclerosis

Parkinson's disease

Normal pressure hydro-cephalus

AIDS: acquired immune deficiency syndrome; CNS: central nervous system; LSD: lysergic acid diethylamide; MAOI: monoamine oxidase inhibitor.

Tsementzis, Differential Diagnosis in Neurology and Neurosurgery © 2000 Thieme All rights reserved. Usage subject to terms and conditions of license.

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