Altered mental status and allied cognitive disorders in HIV-infected patients have devastating consequences for patients and caregivers. Neuropsychological deficits also have a negative impact on the quality of life.  These may arise as a direct effect of HIV infection: for example, as part of a spectrum of HIV-associated neurocognitive disorders (HAND) or as a psychiatric comorbidity (e.g., depression or alcohol/substance abuse). While HIV-related opportunistic infections and neoplasms may also present with progressive cognitive decline and personality changes, more often they manifest as an acute or subacute neurologic emergency. Patients are also at risk of ischemic stroke, and this should be considered in the setting of acute neurologic deterioration.
Early detection and treatment of HAND improves prognosis; poor performance in neuropsychological tests is associated with increased mortality.  Diagnosis and prompt treatment of CNS opportunistic infections or tumors are of obvious importance in reducing morbidity and mortality, although patients with CNS opportunistic infections may have a high prevalence of residual cognitive impairment. 
Combination antiretroviral therapy (ART) has reduced the prevalence of the most severe form of HIV cognitive impairment, prolonged survival,   and improved the quality of life of HIV patients presenting with cognitive problems;  and it may improve psychiatric comorbidity such as depression.  ART has also reduced the age-associated risk for HIV-associated dementia (HAD)   and decreased the incidence of CNS opportunistic infections. However, the use of ART itself may occasionally result in altered mental status, either directly as a medication adverse event, or as a consequence of therapy-related immune reconstitution inflammatory syndrome (IRIS).
Psychiatric comorbidity is highly prevalent in HIV-infected individuals. Depression is associated with low compliance with antiretroviral treatments  and, potentially, with a more rapid disease progression.  Patients who are depressed, have anxiety, or have a substance abuse disorder at the time of initiating ART have a poorer virologic response to treatment.  Effective antidepressant therapy improves quality of life and treatment adherence,  and decreases cognitive complaints. 
A number of resources are available that provide information on the assessment of neurologic manifestations in HIV infection, as well as general and specific guidance on the diagnosis and treatment of opportunistic infections. 
http://www.hivguidelines.org/clinical-guidelines/hiv-and-mental-health/cognitive-disorders-and-hiv-aids/ [HIV Clinical Resource: Cognitive disorders and HIV/AIDS]
http://www.hivguidelines.org/clinical-guidelines/hiv-and-mental-health/depression-and-mania-in-patients-with-hivaids/ [HIV Clinical Resource: Depression and mania in patients with HIV/AIDS]
http://www.nccc.ucsf.edu/hiv_clinical_resources/guidelines/ [National HIV/AIDS Clinicians' Consultation Center: Guidelines]
http://www.eacsociety.org/Portals/0/Guidelines_Online_131014.pdf [European AIDS Clinical Society: guidelines (2013)]
http://cid.oxfordjournals.org/content/56/7/1004 [Mind Exchange Working Group: assessment, diagnosis and treatment of human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND)]