PATHOGENS

• HIV can cause distal sensory neuropathy (HIV-DSP).
• HIV productively infects perivascular macrophages in both central and peripheral nervous system (PNS): degree of macrophage activation correlates w/ Sx.
• HIV DNA demonstrated in perineuronal macrophages in dorsal root ganglia of pts with HIV-associated sensory neuropathy.
• Direct mechanism of neuronal injury may be related to the HIV protein, gp120, which can act as modifier of response to inflammatory cytokines.
• HIV, HCV: cause vasculitic neuropathy, but rare.
• VZV: Post-herpetic neuralgia experienced by some pts.
• Immune-mediated neuropathies (less common): Guillane-Barre Syndrome (GBS) and chronic inflammatory demyelinating neuropathy (CIDP).
• Antiretroviral distal sensory neuropathy (ARV-DSP): Can be caused by NRTIs (d4T and ddI). Some studies have also shown neurotoxicity with some PIs (IDV, SQV, and RTV). Exact mechanism of injury unknown, but thought to be due to mitochondrial toxicity from dysfunction of mitochondrial oxidative metabolism.
• Higher rates of entrapment neuropathies: ulnar neuropathy at elbows, median neuropathy of hands (carpal tunnel syndrome), peroneal neuropathy in legs.
• Non-HIV-related causes: impaired glucose tolerance, diabetes, vitamin deficiency (B12), alcoholism, thyroid dysfunction, syphilis, other medications (e.g. INH).