Dementia: main causes Mnemonic

VITAMIN D VEST:

Vitamin deficiency (B12, folate, thiamine)
Intracranial tumour
Trauma (head injury)
Anoxia
Metabolic (diabetes)
Infection (postencephalitis, HIV)
Normal pressure hydrocephalus

Degenerative (Alzheimer's, Huntington's, CJD, etc) 

Vascular (multi infarct dementia)
Endocrine (hypothyroid)
Space occupying lesion (chronic subdural haematoma) 
Toxic (alcohol)