sistent with the diagnosis of major NCD) ha ve decreased sharply. Contributory factors
may include inadequate control of HIV in the central nervous system (CNS), the evolution
of drug-resistant viral strains, the effects of  chronic long-term systemic and brain inflam-
mation, and the effects of comorb id factors such as aging, drug  abuse, past history of CNS
trauma, and co-infections, such as with the hepatitis C virus. Chronic exposure to antiret-
roviral drugs also raises the po ssibility of neurotoxicity, alth ough this has not been defin-
itively established.