• Delirium
• Depression (pseudodementia)
• Vision or hearing impairment

• Altered mental status

Reversible causes

• Hypothyroidism or hyperthyroidism
• Depression
• Drugs, eg, anticholinergics, sedatives, antipsychotics, opioids
• Vitamin B₁₂ or thiamine deficiency
• Hypercalcemia
• Uremic or hepatic encephalopathy
• Space-occupying lesion, eg, brain tumor, subdural hematoma
• Neurosyphilis
• HIV
• Normal pressure hydrocephalus
• Wilson’s disease
• Sleep apnea
• Chronic meningitis

Irreversible causes

• Alzheimer’s disease
• Vascular (multi-infarct) dementia
• Parkinson’s disease
• Dementia with Lewy bodies
• Huntington’s disease
• Frontotemporal dementia, eg, Pick’s disease
• Progressive supranuclear palsy
• Creutzfeldt-Jakob disease