Microvasculitis in non-diabetic lumbosacral radiculoplexus neuropathy (LSRPN): Similarity to the diabetic variety (DLSRPN)

Diabetic lumbosacral radiculoplexus neuropathy (DLSRPN) has been shown to b e due to ischemic injury from microvasculitis. The present study tests whet her ischemic injury and microvasculitis are the pathologic cause of non-dia betic lumbosacral radiculoplexus neuropathy (LSRPN), and whether the pathol ogic alterations are different between LSRPN and DLSRPN. We studied distal cutaneous nerve biopsies of 47 patients with LSRPN and compared findings wi th those of 14 age-matched healthy controls and 33 DLSRPN patients. In both disease conditions, we found evidence of ischemic injury (multifocal fiber degeneration and loss, perineurial degeneration and scarring, characterist ic fiber alterations, neovascularization, and injury neuroma) that we attri bute to microvasculitis (mural and perivascular mononuclear inflammation of microvessels, inflammatory separation, fragmentation and destruction of mu ral smooth muscle, and previous microscopic bleeding [hemosiderin]). Teased nerve fibers in LSRPN showed significantly increased frequencies of axonal degeneration, segmental demyelination, and empty nerve strands. The segmen tal demyelination appeared to be clustered on fibers with axonal dystrophy. The nerves with abnormal frequencies of demyelination were significantly a ssociated with nerves showing multifocal fiber loss. We reached the followi ng conclusions: 1) LSRPN is a serious condition with much morbidity that mi rrors DLSRPN. 2) Ischemic injury from microvasculitis appears to be the cau se of LSRPN. 3) Axonal degeneration and segmental demyelination appear to b e linked and due to ischemia. 4) The pathologic alterations in LSRPN and DL SRPN are indistinguishable, raising the question whether these 2 conditions have a common underlying mechanism, and whether diabetes mellitus contribu tes to the pathology or is a risk factor in DLSRPN. 5) Both LSRPN and DLSRP N are potentially treatable conditions.