The evolving, and eventually severe, impairment of immune defenses caused by HIV-1 renders the nervous system highly vulnerable to a broad spectrum of disorders. The following overview emphasizes general principles of pathogenesis and approach to diagnosis.

Pathophysiology
A number of pathophysiologic processes may lead to neurologic dysfunction in the late phase of HIV-1 infection (Table 411-1) . These include conditions that distinguish the AIDS patient from other groups, such as opportunistic infections, opportunistic neoplasms, and several conditions that appear to relate to more direct effects of HIV-1 itself.

AIDS patients are also susceptible to the neurologic conditions that affect other acute and chronically ill populations, including metabolic brain disease resulting from systemic organ dysfunction, stroke related to nonbacterial thrombotic endocarditis or coagulopathies, toxic effects of medications, and primary psychiatric disturbances. Here we focus on those disorders that particularly distinguish AIDS patients.