Vitamin deficiencies

Thiamine (B₁): Wernicke's encephalopathy^a

B₁₂ (subacute combined degeneration)^a

Nicotinic acid (pellagra)^a

Endocrine and other organ failure

Hypothyroidism^a

Adrenal insufficiency and Cushing's syndrome^a

Hypo- and hyperparathyroidism^a

Renal failure^a

Liver failure^a

Pulmonary failure^a

Chronic infections

HIV

Neurosyphilis^a

Papovavirus (JC virus) (progressive multifocal leukoencephalopathy)

Tuberculosis, fungal, and protozoal^a

Whipple's disease^a

Head trauma and diffuse brain damage

Chronic traumatic encephalopathy

Chronic subdural hematoma^a

Postanoxia

Postencephalitis

Normal-pressure hydrocephalus^a

Intracranial hypotension

Neoplastic

Primary brain tumor^a

Metastatic brain tumor^a

Paraneoplastic/autoimmune limbic encephalitis^a

Toxic disorders

Drug, medication, and narcotic poisoning^a

Heavy metal intoxication^a

Organic toxins

Psychiatric

Depression (pseudodementia)^a

Schizophrenia^a

Conversion disorder^a

Degenerative disorders

Huntington's disease

Multisystem atrophy

Hereditary ataxias (some forms)

Frontotemporal lobar degeneration spectrum

Multiple sclerosis

Adult Down's syndrome with Alzheimer's disease

ALS-parkinsonism-dementia complex of Guam

Prion (Creutzfeldt-Jakob and Gerstmann-Sträussler-Scheinker diseases)

Miscellaneous

Sarcoidosis^a

Vasculitis^a

CADASIL, etc.

Acute intermittent porphyria^a

Recurrent nonconvulsive seizures^a

Additional conditions in children or adolescents

Pantothenate kinase-associated neurodegeneration

Subacute sclerosing panencephalitis

Metabolic disorders (e.g., Wilson's and Leigh's diseases, leukodystrophies, lipid storage diseases, mitochondrial mutations)