Dementia
Introduction
Dementia can be defined in several ways but all include the following elements:
The incidence is 50 per 100 000 population but is strongly age-related, being rare under the age of 60 years. The most common causes are neurodegenerative conditions, especially Alzheimer’s disease (AD), Lewy body disease (LBD) and diffuse cerebrovascular disease. An unusual cause should be suspected in patients under 55, where progression is rapid or if other features are present (Table 1). Most neurodegenerative conditions can only be diagnosed with certainty by neuropathological examination. Most of these conditions progress slowly over many years so the prevalence and social burden of the condition are very high.
Table 1 Dementias associated with prominent physical abnormalities
| Clinical feature | Condition | Associated features |
| Apraxic gait disorder or Parkinsonism | Frontal lobe tumour Hydrocephalus Cerebral arteriosclerosis Parkinson’s disease/cortical Lewy body disease Wilson’s disease | |
| Myoclonus | ||
| Chorea | ||
| Ataxia | Wernicke–Korsakoff syndrome | See above |
| Supranuclear gaze palsy | ||
| Neuropathy/spinal cord syndrome | Vitamin B12 and folic acid deficiency | Usually raised mean red blood cell volume |
| Weakness and fasciculation | Motor neurone disease (MND) dementia | Evolves to MND with dementia (p. 108) |
