Evaluation of peripheral and central olfactory pathways in HIV-infected patients by MRI

To investigate peripheral and central olfactory pathways using cranial magnetic resonance imaging (MRI) in human immunodeficiency virus (HIV)-infected patients.

The cranial MRI images of 37 HIV-infected adult patients and 37 adults without HIV infection having normal cranial MRI results were included in the study. In both groups, olfactory bulb (OB) volume and olfactory sulcus (OS) depth; and insular gyrus and corpus amygdala areas were measured using cranial MRI. In the HIV group, disease duration, HIV RNA, and CD4 lymphocyte count and levels as a percentage were also recorded.

The HIV group had significantly lower bilateral OB volumes, insular gyrus and corpus amygdala areas compared to the control group. The HIV group showed positive correlations between OB volumes, OS depths, insular gyrus, and corpus amygdala areas bilaterally. Increases in OB volumes and OS depths were associated with an increase in the insular gyrus area. The corpus amygdala and insular gyrus areas increased similarly. There was no significant correlation between age, gender, disease duration, CD4 lymphocyte count and per cent, HIV RNA values, and the measurement values of the central and peripheral olfactory regions.

A decrease in olfactory regions of OB, insular gyrus, and corpus amygdala in HIV-infected patients shows that HIV infection may cause olfactory impairment. There is no correlation between disease duration and olfactory impairment. It may be related to neuroinflammation, HIV-related brain atrophy, acquired immunodeficiency syndrome (AIDS) dementia complex, or neurocognitive impairment, which are the other explanations for the olfactory impairment in HIV. The possible toxicity from antiretroviral therapy (ART) may be another cause that should be investigated further.