These changes were observed in people who were not neuropsychologically impaired. Most of the subjects (75%) had an undetectable viral load, and the differences did not correlate with any known markers of HIV disease, according to researchers led by Beau Ances, MD, PhD, clinical instructor and NeuroAIDS fellow, HIV Neurobehavioral Research Center, University of California, San Diego, United States.

Their goal was to detect HIV-related changes in the brain before those changes became apparent on standard neuropsychological tests, Dr. Ances said in a poster presentation on February 28^th.

The researchers enrolled 11 men and 1 woman who were HIV positive and neurocognitively normal, and 10 men and 2 women who were age-matched and seronegative.

Each participant underwent blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI). Changes in cerebral blood flow and oxygen consumption were monitored simultaneously with the fMRI studies during the brain function test.

For the test, each subject watched numbers flickering on a screen at 2 Hz and pressed a button on a response box corresponding to the number on the screen at any given moment. As they were doing this, subjects also were undergoing BOLD-fMRI and measurement of their changes in cerebral metabolism.

The lenticular nucleus was of particular interest because HIV is known to affect this area, leading to characteristic changes in neuropsychological performance.

The imaging studies showed no correlation between quantitative fMRI changes and viral load or CD4 levels in the HIV-positive individuals. However, cerebral blood flow in the lenticular nucleus increased by 50% in the people with HIV, compared with a 30% increase in the control subjects. The rate of cerebral metabolic oxygen consumption increased by about 27% in the HIV group and by 15% in controls (P < .05 for both).

These findings suggest that even unimpaired HIV-positive individuals whose viral loads are kept under control with antiretroviral agents may experience increased cerebral metabolic demand when performing a mentally challenging task, said Dr. Ances.

He suggested that HIV-infected patients be evaluated with fMRI, and that early neuroprotective therapies be considered before patients begin showing signs of neurological impairment.


[Presentation title: Cerebral Blood Flow and Metabolism are Elevated in the Lenticular Nuclei of Unimpaired HIV+ Subjects. Poster 377]

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