Vascular changes in the cerebral cortex in HIV-1 infection: I. A morphometric investigation by light and electron microscopy.

The microvasculature of the cerebral cortex in AIDS brains was investigated by means of stereology at the light and electron microscopic levels. Stereologic parameters for microvessels were determined in formalin-fixed autopsy tissue of 24 AIDS patients and of 35 age- and sex-matched controls. At the light microscopic level these encompassed the measurement of the diameter, volume fraction, surface area density, and length density; at the electron microscopic level profile area, perimeter, diameter of capillaries, endothelial cells, pericytes, and basal lamina as well as the mean thickness of the basal lamina were measured. In AIDS brains a significant increase in the diameter of cortical vessels was noted. The surface area density (Sv) and volume fraction (Vv) of microvessels were likewise significantly increased in AIDS brains. No changes were noted for the length density (Lv) which also indicates that no changes in the number of vessels occur in HIV-1 infection. Ultrastructural thinning of the basal lamina was a consistent finding. Vacuoles occurred in the basal lamina of capillaries and increased in number and size in AIDS brains. Using morphometric methods, significant changes of cortical vessels are detectable at the light and electron microscopic level. These changes most probably represent the morphological substrate of an altered blood-brain-barrier in AIDS brains and may account for the reported hypoperfusion demonstrated in SPECT analyses.