The definition of dementia is a broad one, and it is not surprising, therefore, that the syndrome can be associated with a large variety of diseases. All of these may be associated with widespread cognitive impairment, but the clinical patterns vary and can lead to characteristic features. A broad distinction has been drawn between subcortical and cortical dementias (Albert et al. 1974; Cummings 1986).

The term ‘subcortical dementia’ was originally applied to the cognitive deficits seen in progressive supranuclear palsy and Huntington's disease, and is characterized by a marked slowness in cognition with additional impairments of motivation and attention. Indeed, if the patient is allowed time, then performance on routine neuropsychological testing may improve, but performance in everyday life remains severely compromised.

The diseases that are most commonly found with this type of dementia are those affecting the basal ganglia and frontal connections. Dysphasia, dyspraxia, and agnosia are not prominent in these patients, by contrast to those with cortical dementia, in whom the memory impairment is generally not improved by cues, and the speed of cognition is relatively normal. The prototypic cortical dementia is Alzheimer's disease and the characteristic clinical pattern reflects damage to the cortical association areas.

Primary cerebral degenerations

  • Alzheimer's disease
  • Down syndrome and Alzheimer histopathology
  • Pick's disease
  • Progressive supranuclear palsy
  • Corticobasal degeneration
  • Frontal lobe degeneration
  • Dementia with motor neuron disease inclusions
  • Parkinsonism-dementia complex of Guam
  • Parkinson's disease and dementia
  • Dementia with Lewy bodies
  • Thalamic degeneration
  • Calcification of the basal ganglia with neurofibrillary tangles
  • Huntington's disease
  • Spinocerebellar degenerations
  • Progressive myoclonic epilepsy

Cerebral infections and inflammatory disorders

  • Neurosyphilis
  • Viral encephalitis especially herpes simplex
  • HIV infection
  • Progressive multifocal leucoencephalopathy
  • Subacute sclerosing panencephalitis
  • Subacute rubella encephalitis
  • Viral, bacterial, and fungal meningitides
  • Whipple's disease
  • Behçet's syndrome
  • Disseminated encephalomyelitis
  • Multiple sclerosis
  • Sarcoidosis

Prion dementias

  • Sporadic and familial Creutzfeldt-Jakob disease
  • Gerstmann-Straussler-Schenke syndrome
  • Kuru
  • Iatrogenic Creutzfeldt-Jakob disease
  • Variant Creutzfeldt-Jakob disease
  • Familial fatal insomnia

Cerebrovascular disease

  • Multiple cortical infarcts
  • Binswanger's disease
  • Congophilic angiopathy including hereditary Dutch amyloid angiopathy
  • Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL)
  • Cranial arteritis
  • Cerebral arteritides inc PAN, SLE, thromboangiitis obliterans, and granulomatous angiitis
  • Thrombotic thrombocytopenic purpura
  • Subacute diencephalic angioencephalopathy
  • Subdural haematoma
  • Giant aneurysms
  • Arteriovenous malformations
  • Hyperviscosity syndromes

Inherited metabolic and storage disorders

  • Porphyria
  • Wilson's disease
  • Mitochondrial cytopathies
  • Kuf's disease
  • Metachromatic and adrenoleucodystrophy
  • Membranous lipodystrophy
  • Cerebrotendinous xanthomatosis

Metabolic and toxic causes (the majority more commonly present as confusional states)

  • Hypothyroidism
  • Hyper- and hypocalcaemia
  • Hypoglycaemia
  • Hypo- and hypernatraemia
  • Uraemia
  • Dialysis dementia
  • Chronic hepatic encephalopathy
  • Hashimoto's encephalopathy
  • Wernicke-Korsakoff syndrome
  • Alcoholic dementia
  • Marchiafava-Bignami disease
  • Hypoxia
  • Drugs, poisons, heavy metals
  • Vitamin B12 deficiency
  • Pellagra
  • Malabsorption syndrome and coeliac encephalopathy


  • Meningiomas
  • Gliomas especially callosal
  • Parapituitary tumours
  • Pineal and midbrain tumours
  • Cerebral lymphoma
  • Cerebral metastases
  • Carcinomatous meningitis
  • Paraneoplastic syndromes including limbic encephalitis


  • Aqueduct stenosis
  • Normal pressure hydrocephalus
  • Open and closed head injuries
  • Dementia pugilistica
  • Post-cerebral irradiation