Other types of dementia

Other types of dementia

Vascular dementia (multiple infarct dementia):
Intellectual decline due to an ischaemic injury to the brain. Second most common form of dementia. The cognitive decline is the result of additive effect of infarcts  loss of brain tissue. Abrupt onset. Higher risk in those with diabetes mellitus, hypertension, ischaemic heart disease, stroke (increases risk 9x), smoking, falls, hyperlipidemia, early urinary incontinence ( importance of primary prevention in these populations). Deterioration is selective – some functions can remain intact, depending on location of infarcts. Similar clinical features to Alzheimer's, but onset more abrupt and has a more fluctuating course. Symptoms often develop in a stepwise fashion.

Diagnostic criteria:
1) Dementia
2) Two or more of:
i) Focal neurological signs
ii) Onset was abrupt, stepwise or associated with a stroke
iii) CT or MRI shows multiple infarcts

Management – not possible to reverse damage that has already occurred, but further damage may be preventable by addressing risk factors (eg control of hypertension and diabetes; anticoagulants).

Dementia associated with Lewy Body Disease
Lewy bodies (eosinophilic intracytoplasmic neuronal inclusions) are commonly associated with Parkinson’s disease. Lewy body dementia was first described in 1961 – as a diagnosis, it is increasing in incidence, but still may be poorly understood. Clinically similar to Alzheimer’s disease - loss of memory, language and reasoning and other higher brain functions. Confusion tends to fluctuate; visual hallucinations may occur.

Two of the following are needed for diagnosis of probable Lewy Body Dementia:
• fluctuating cognition with variations in attention and alertness
• recurrent visual hallucinations (usually well formed and in great detail)
• motor features of Parkinsonism

No definitive treatment, but have high sensitivity to antipsychotics

Other uncommon causes of dementia:
• toxins (eg lead)
• Vitamin deficiencies (eg B12, B1, B6)
• endocrine (eg hypo- or hyperthyroidism, hyperparathyroidism, Cushing’s disease)
• metabolic conditions (eg hyponatraemia, renal failure)
• Huntingtons disease
• vasculopathies affecting the brain
• CNS infections (eg Creutzfeldt-Jacob, AIDS)
• CNS lesions