Optic nerve axonal pathology is related to abnormal visual evoked responses in AIDS
Electrophysiological studies in subjects with HIV/AIDS demonstrate subtle changes in the visual pathway even in the absence of visual symptoms. But the pathological correlate of the electrophysiological abnormalities is largely unknown. This study attempts to correlate pathological changes in the retina and intraorbital portion of optic nerve in four drug naïve patients of AIDS caused by HIV-1 clade C, who had abnormalities in the visual evoked potentials recorded antemortem. Three had no visual complaints and one patient had sudden loss of vision in the right eye. In all four patients, the visual evoked potentials disclosed variable prolongation of P100 latencies. Histologically axonal cytoskeletal breakdown and depletion in the optic nerves was the cardinal finding with variable myelin loss, even in the absence of overt visual dysfunction, or infective retinitis. The axonal loss was maximal in the symptomatic case. Retinal ganglion cell depletion was seen in only two patients. Sectoral infiltration of the optic nerve by cryptococci and Cryptococcal choroiditis was the only opportunistic infection to involve the eye. Axonal pathology in the optic nerve appears to be related to the abnormalities recorded in visual evoked potentials even in the absence of overt clinical symptoms. Opportunistic infections could be contributing to the axonal pathology in the optic nerve in patients with AIDS.
KeywordsVisual evoked potentials Optic nerve Axonal loss Demyelination Opportunistic infections Cryptococcal optic neuritis
The authors acknowledge financial help from the Human Brain Tissue Repository (Human Brain/Tissue Fluid Bank), Department of Neuropathology, National Institute of Mental Health & Neurosciences, Bangalore. This publication was partly supported by a subcontract from The Johns Hopkins University, through grant no: R21
MH071213 from the National Institute of Health (NIH), National Institute of Mental
Health (NIMH) and Fogarty International Centre (FIC). The authors also wish to thank Manjunath K for assistance with photography and Nagesh HN for technical assistance.
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