MORPHOMETRIC ANALYSIS OF THE PERIPHERAL NEUROPATHY OF AIDS

A morphometric study of the peripheral nervous system at autopsy was u ndertaken in 11 AIDS patients and 10 controls, The left L4, L5, and Sf dorsal root ganglia (DRG) and samples of the sciatic nerve at the but tock, tibial nerve at the knee, and sural nerve at the ankle were coll ected. Indices of neuronal/axonal degeneration and of segmental demyel ination/ remyelination were measured at each level. The small number o f cases and evidence of neuropathy in a number of the control cases re sulted in statistical significance for only a limited number of compar isons. Nodules of Nageotte in the DRG were increased fivefold in AIDS cases compared with controls, and axonal degeneration in single-teased nerve fibers was increased 9-fold in the sciatic nerve, 28-fold in th e tibial nerve, and 12-fold in the sural nerve. The ratios of AIDS to controls for the density of remaining DRG neurons and large myelinated axons were reduced to 0.71 in the DRG, 0.84 in the sciatic nerve, 0.8 4 in the tibial nerve, and 0.66 in the sural nerve. Axonal regeneratio n in single-teased nerve fibers was increased threefold at the sciatic nerve level in AIDS, but was markedly reduced at distal levels. Acute segmental demyelination in single-teased nerve fibers was present to a greater extent than in controls at all levels of the peripheral nerv es in the AIDS cases. Remyelinating fibers were increased compared wit h controls only in the proximal sciatic nerve, No case showed the chan ges of cytomegalovirus infection. In a parallel immunohistochemical st udy of these AIDS peripheral nerves, T-cell and macrophage infiltratio n, with cytokine expression, was demonstrated. The pathological proces s in the neuropathy of terminal AIDS appears to be a multifocal immuno logically mediated inflammatory disease, with increased density of mac rophages and T cells at all levels of the peripheral nervous system, p roducing segmental demyelination and axonal degeneration. Reparative p rocesses (axonal regeneration and remyelination) occurred only at the most proximal levels of the nerves. (C) 1998 John Wiley & Sons, Inc.