(p. 427) HIV-Associated Neurocognitive Disorders 

HIV causes a chronic form of encephalitis (HIVE) that is clinically characterized by either dementia or mild neurocognitive impairment. Since the introduction of antiretroviral therapy in 1996, the incidence of HIV dementia has decreased by 50%, but the prevalence of mild neurocognitive disorder has increased up to 39%. HIVE is the result of direct microglial infection, interruption of trophic factors, or caused by inflammatory cytokines. HIV enters the brain primarily by the “Trojan horse mechanism”; it is carried by monocytes and lymphocytes that cross the blood–brain barrier. HIV has a predilection for the basal ganglia, deep white matter, and hippocampus, resulting in a subcortical dementia. HIV dementia is a diagnosis of exclusion and other co-infections, cerebrovascular disease, malnutrition, and drug abuse should be ruled out before making the diagnosis. In patients receiving antiretroviral therapy with immunological response, a novel condition termed CD8⁺ T cell encephalitis was recently described.