Diagnostic imaging contribution in the early stages of HIV infection of the brain.

The neuropathology of full-blown, symptomatic AIDS, established in many large autopsy series, has been described in great detail and is now universally accepted. In contrast, the natural history of the changes occurring in the central nervous system during the earlier states of HIV-1 infection remains poorly understood. With specific regard to MR imaging, structural abnormalities have been reported early in the course of the illness, with variable incidence, making it difficult to appreciate the significance of these findings, in particular for neurologically asymptomatic individuals. This article analyzes successively neuropathologic studies at the early stages of brain involvement by HIV and shows how imaging techniques contribute to the understanding of what is going on during the so-called "asymptomatic" period, lasting from seroconversion to symptomatic AIDS. The complementary use of clinical imaging and new technical modalities, such as proton spectroscopy MR imaging or functional MR imaging, will provide more specific and sensitive analyses. Animal studies also will contribute in the future by providing a better knowledge of the natural history of the illness and providing a means for testing the efficacy of new medication.