Human Immunodeficiency Virus (HIV) is a Retrovirus that contains single stranded RNA (ssRNA). It was first isolated in 1983, and current WHO estimates state that over 36 million people are living with HIV worldwide. There are 2 main types of HIV: HIV-1 is more aggressive, and is responsible for the overwhelming majority of HIV cases worldwide; HIV-2 is mainly limited to a few West African countries, and has infected approximately 1-2 million people worldwide. There are significant genetic differences between the HIV-1 and HIV-2, to the point where some HIV medications do not work on HIV-2 infected patients; furthermore, HIV-2 typically has a slower progression and lower viral load.
The natural course of HIV typically starts with an acute HIV infection through infected body fluids, such as blood, semen, seminal fluid, vaginal/rectal secretions come, etc. contact an individual’s broken skin, vagina, rectum, foreskin, opening of the penis, etc. Typically in the primary acute infection, flu-like symptoms generally appear a few weeks after exposure and can last anywhere from 1 week to months.
The second stage of HIV infection is a latent stage, which is the category most HIV infected individuals would fall under. This is characterized by a chronic asymptomatic infection where the viral titre is more controlled by the host immune system, however, generalized lymphadenopathy and thrombocytopenia may be present. The Final stage, is a chronic symptomatic stage that is commonly known AIDS (acquired immunodeficiency syndrome). This stage is characterized by a low CD4+ T-cell count, leading to high levels of viral titre, and severe immunosuppression leading to opportunistic infection.
HIV associated neurocognitive disorders is a term used to describe the clinical syndromes related to HIV infection in nervous system cells that lead to different severities of cognitive impairment and functioning. HIV-associated dementia (HAD) is characterized by a combination of cognitive, behavioural and motor dysfunction; typical findings include inattention, apathy, psychomotor slowing, motor slowing and ataxia, among others.
On brain MRI, abnormalities related to HIV/AIDS may be directly from the HIV virus, opportunistic infections, neoplasms in an immunocompromised host, or treatment related complications.
On T2-MRI, symmetric hyperintensity of the periventricular and deep white matter can be seen with sparing of subcortical white matter and posterior fossa structures; it can be confluent or patchy, with no mass effect or enhancement. MR spectroscopy may show increased choline and decreased N-acetyl aspartate peaks, along with changes in glutamine and glutamate levels. HIV-associated cerebral vasculopathy may be seen with an appearance similar to cerebral vasculitis, but without histopathological changes. Leukocytoclastic vasculitis of the vasa vasorum may be identified, and large, medium or small vessels can be affected.
Other abnormalities that may be seen are opportunistic infections due to immunosuppression, such as cerebral toxoplasmosis, Cryptococcal infection, mycobacterial infection, HSV infection, among others. Furthermore, primary CNS lymphomas may be present and it should be differentiated from a cerebral toxoplasmosis. Other findings r
References:
Clifford, D.B., Ances, B.M., 2013. HIV-associated neurocognitive disorder. Lancet Infect.
Dis. 13 (11), 976–986.
https://www.uptodate.com/contents/approach-to-hiv-infected-patients-with-central-nervous-system-lesions#H1
https://www.uptodate.com/contents/epidemiology-transmission-natural-history-and-pathogenesis-of-hiv-2-infection?topicRef=3724&source=see_link
https://www.canada.ca/en/public-health/services/diseases/hiv-aids.html
https://radiopaedia.org/articles/hiv-associated-dementia