This a cross-sectional study to determine the prevalence of HIV-related Neurological Disorders in the countries of the Asia-Pacific Region. Researchers will visit each country site for a period of 2-3 weeks and work with local investigators. Outpatients will be evaluated once-only for the presence of HIV-related symptomatic peripheral neuropathy and HIV-related Neurocognitive Impairment. Inpatients at the sites will be evaluated once-only for the presence of HIV dementia, cerebral toxoplasmosis, cerebral tuberculosis, cryptococcal meningitis, lymphoma, PML and CMV encephalitis.

The Primary outcomes are:

1. To determine the prevalence of HIV-related neurocognitive impairment and ADC at the APNAC-10 sites
2. To determine the prevalence of symptomatic peripheral sensory neuropathy at the APNAC-10 sites
3. To determine the prevalence of central nervous system opportunistic infections and tumours at the APNAC-10 sites

The secondary outcomes are:

To determine the degree of cognitive impairment in patients presenting with HIV-related cognitive impairment at the APNAC-10 sites

• To determine the CD4 cell counts, HIV viral loads HIV viral loads and prior AIDS defining illnesses (ADIs) of patients presenting with HIV-related neurocognitive impairment and ADC at the APNAC-10 sites
• To compare the prevalence of HIV-related neurocognitive impairment and ADC at the APNAC-10 sites to the published pre-HAART prevalence of these conditions in developed countries
• To compare the prevalence of HIV-related neurocognitive impairment and ADC between the APNAC-10 sites
• To describe the severity of symptoms of patients presenting with symptomatic peripheral sensory neuropathy at the APNAC-10 sites
• To determine the CD4 cell counts, HIV viral loads HIV viral loads and prior ADIs of patients presenting with symptomatic peripheral sensory neuropathy at the APNAC-10 sites
• To determine what proportion of symptomatic peripheral sensory neuropathy may be ascribed to HIV alone, to the use of nucleoside analogues
• To compare the prevalence of symptomatic peripheral sensory neuropathy at the APNAC-10 sites to the published pre-HAART prevalence of these conditions in developed countries
• To compare the prevalence of symptomatic peripheral sensory neuropathy between the APNAC-10 sites
• To determine the prevalence of asymptomatic peripheral neuropathy
• To describe the presenting symptoms and signs of patients presenting with CNS OIs and tumours at the APNAC-10 sites
• To describe the neuroradiological findings of patients presenting with CNS OIs and tumours at the APNAC-10 sites
• To determine the serological, culture and other diagnostic test results of patients presenting with CNS OIs and tumours at the APNAC-10 sites
• To determine the CD4 cell counts, HIV viral loads and prior ADIs of patients presenting with CNS OIs and tumours at the APNAC-10 sites
• To compare the prevalence of CNS OIs and tumours at the APNAC-10 sites to the published pre-HAART prevalence of these conditions in developed countries
• To compare the prevalence of CNS OIs and tumours between the APNAC-10 sites