Neurologic and psychiatric manifestations of HIV disease. Neuropsychiatric problems have assumed an increasingly prominent role in HIV-infected individuals. Disease occurs at all levels of the central and peripheral nervous systems by a variety of mechanisms. The AIDS dementia complex is the prototypical example of "direct" effects of HIV on the neuraxis, while infections such as toxoplasmosis and cryptococcal meningitis are complications of HIV-induced immunosuppression. Neurologic manifestations vary in frequency depending upon the overall stage of HIV disease; diagnostic difficulties may be encountered because of HIV's effect on cerebrospinal fluid parameters. The uncertainties of management of neurosyphilis in this setting provide and example of these problems. As is the case with other organ systems, the main goal of neurodiagnostic efforts is to find the increasing number of treatable components of neuropsychiatric dysfunction. 