Microvasculitis and ischemia in diabetic lumbosacral radiculoplexus neuropathy

Objective: To determine whether microscopic vasculitis explains the clinical and pathologic features of diabetic lumbosacral radiculoplexus neuropathy (DLSRPN). Background: DLSRPN is usually attributed to metabolic derangement or ischemic injury, but microscopic vasculitis as the sole cause needs consideration. Methods: We prospectively studied the clinical, laboratory, and EMG features as well as the pathology of distal cutaneous nerve biopsy specimens of patients with DLSRPN. Results: Study of DLSRPN nerve biopsy specimens (n = 33) compared with those from healthy controls (n = 14) and those with diabetic polyneuropathy (n = 21) provided strong evidence for ischemic injury (axonal degeneration, multifocal fiber loss, focal perineurial necrosis and thickening, injury neuroma, neovascularization, and swollen fibers with accumulated organelles), which we attribute to microscopic vasculitis (epineurial vascular and perivascular inflammation, vessel wall necrosis, and evidence of previous bleeding). Segmental demyelination was significantly associated with multifocal fiber loss. Conclusions: 1) This severe, debilitating neuropathy begins with symptoms unilaterally and focally in the leg, 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 radiculoplexus neuropathy). 2) Motor, sensory, and autonomic fibers are all involved. 3) Ischemic injury explains the clinical features and pathologic abnormalities of nerve. 4) The proximate cause of the ischemic injury appears to be microscopic vasculitis. 5) The segmental demyelination is probably secondary to ischemic axonal dystrophy, thus providing a unifying hypothesis for both axonal degeneration and segmental demyelination.