Microvasculitis and ischemia in diabetic lumbosacral radiculoplexus neuropathy

Objective: To determine whether microscopic vasculitis explains the clinica l and pathologic features of diabetic lumbosacral radiculoplexus neuropathy (DLSRPN). Background: DLSRPN is usually attributed to metabolic derangemen t or ischemic injury, but microscopic vasculitis as the sole cause needs co nsideration. Methods: We prospectively studied the clinical, laboratory, an d EMG features as well as the pathology of distal cutaneous nerve biopsy sp ecimens of patients with DLSRPN. Results: Study of DLSRPN nerve biopsy spec imens (n = 33) compared with those from healthy controls (n = 14) and those with diabetic polyneuropathy (n = 21) provided strong evidence for ischemi c injury (axonal degeneration, multifocal fiber loss, focal perineurial nec rosis and thickening, injury neuroma, neovascularization, and swollen fiber s with accumulated organelles), which we attribute to microscopic vasculiti s (epineurial vascular and perivascular inflammation, vessel wall necrosis, and evidence of previous bleeding). Segmental demyelination was significan tly associated with multifocal fiber loss. Conclusions: 1) This severe, deb ilitating neuropathy begins with symptoms unilaterally and focally in the l eg, thigh, or buttock and spreads to involve the other regions of the same and then opposite side and is due to multifocal involvement of lumbosacral roots, plexus, and peripheral nerve (i.e., diabetic lumbosacral radiculople xus neuropathy). 2) Motor, sensory, and autonomic fibers are all involved. 3) Ischemic injury explains the clinical features and pathologic abnormalit ies of nerve. 4) The proximate cause of the ischemic injury appears to be m icroscopic vasculitis. 5) The segmental demyelination is probably secondary to ischemic axonal dystrophy, thus providing a unifying hypothesis for bot h axonal degeneration and segmental demyelination.