ALTERED CORTICAL BLOOD-FLOW IN HIV-SEROPOSITIVE INDIVIDUALS WITH AND WITHOUT DEMENTIA - A SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY STUDY

Objective: To quantitatively demonstrate the pattern of cerebral perfu sion abnormalities in HIV-1-infected individuals described as 'patchin ess' or inhomogeneity in previous qualitative emission tomographic ima ging studies. Design: We aimed to create a quantitative measure of inh omogeneity in HIV-infected individuals. High-frequency variance in cor tical profiles is an indication of inhomogeneity in the distribution o f radiotracer in the cerebral cortex. Therefore, the study analysis wa s designed to enable the estimation of variance frequencies in cortica l profiles. Methods: Regional cerebral blood flow was examined in nine mildly demented and 10 cognitively normal HIV-1-seropositive individu als and eight seronegative normal controls using single photon emissio n computed tomography with the radiotracer [I-123]-N-isopropyl-p-lodoa mphetamine. Quantitative analysis was performed using circumferential profiles of cerebral cortical perfusion. Fourier transform power spect ra of the profiles were examined as an index of patchiness in tracer d istribution. Results: Normal controls were characterized by strong mid dle frequency and weak high-frequency power. Both HIV-1-infected group s showed a significant power shift from middle to high frequencies. Co nclusions: Increased high-frequency variations in both HIV-1-infected groups indicates diffuse cortical perfusion changes compared with norm al controls. This study suggests that there are cerebral bloodflow abn ormalities in HIV-1-infected individuals both with and without clinica lly severe dementia.