The dementia of Creutzfeldt-Jakob disease (CJD) arises from exposure to infective prions. There are four main types of CJD, also classed as prion diseases or transmissible spongiform encephalopathies (TSEs). Prions have been described as “abnormal, pathogenic agents that are transmissible and are able to induce abnormal folding of specific normal cellular proteins called prion proteins that are found most abundantly in the brain.”^15,16

HIV-associated cognitive impairment or dementia is now very rare (affecting 2% of people with HIV) due to earlier access to antiviral treatments. It is more likely in people who start treatment with a very low CD4 count placing theme at greater risk from HIV-induced brain damage or to other opportunistic brain infections.¹⁷

Some types of dementia may be reversible in a proportion of patients if the primary cause is removed or treated. Examples include vitamin B1 (thiamine) or B12 deficiency, iron deficiency, thyroid dysfunction, depression (presenting as a ‘pseudo-dementia’), increased pressure on the brain (normal pressure hydrocephalus) or medicine adverse effects, such as with steroids or drugs with anticholinergic actions.^18,19