Final answer:
The patient is in stage 3 of HIV infection, also known as acquired immunodeficiency syndrome (AIDS), and is experiencing neurologic complications. These symptoms are consistent with HIV-associated neurocognitive disorders (HAND) or opportunistic infections like toxoplasmosis.
Step-by-step explanation:
This patient is in stage 3 of HIV infection, known as acquired immunodeficiency syndrome (AIDS). The criteria for diagnosis of AIDS is a CD4 T-cell count below 200 cells/μL or the development of certain opportunistic illnesses. The patient's subacute mental status changes, motor deficits, ataxia, and multiple non-enhancing brain lesions on CT are consistent with HIV-related neurologic complications such as HIV-associated neurocognitive disorders (HAND) or opportunistic infections like toxoplasmosis.