Vertebral Ischemic Necrosis in Diabetic Lumbosacral Radiculoplexus Neuropathy
- 1Division of Neurology, Department of Medicine, The Ottawa Hospital, Ottawa, Ontario, Canada
- 2Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
- 3Division of Neuroradiology, Department of Radiology, The Ottawa Hospital, Ottawa, Ontario, Canada
- 4Department of Pathology and Laboratory Medicine, The Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada
- Corresponding author: Ari Breiner, abreiner{at}toh.ca
Diabetic lumbosacral radiculoplexus neuropathy (DLRPN), or diabetic amyotrophy, is an infrequent neurovascular complication of diabetes thought to result from immune-mediated infarction of peripheral nerve branches (1). DLRPN has not previously been reported in association with infarction of the vertebral bone, which itself is a rare occurrence, typically in the setting of aortic surgery and spinal cord infarction (2). We report a case of simultaneous DLRPN and vertebral bony infarction in a patient with type 2 diabetes, highlighting the unifying vascular etiology responsible for both these uncommon pathologies.
A 47-year-old man of Nepalese origin presented to hospital with a 2-week history of relatively acute-onset left lumbar pain, numbness and paresthesia in the left obturator and saphenous nerve distributions, and marked proximal left leg weakness. His past health was notable for a 4-year history of type 2 diabetes, well controlled with sitagliptin, canagliflozin, and metformin. On examination, there was Medical Research Council (MRC) grade 2/5 paresis of the left hip flexor and hip adductor muscles, with grade 1/5 power of knee extension. The left patellar reflex was absent. Electrodiagnostic studies showed a reduced left femoral motor potential and denervation at the level of L1–L4 myotomes. The clinical and electrodiagnostic findings were in keeping with DLRPN.
MRI studies of the lumbosacral spine (Fig. 1a and b) demonstrated serpiginous, heterogenous T1 and T2 signal with contrast enhancement in the posterior and left aspects of the L4 vertebral body. This was felt to be most in keeping with infarction. There was soft tissue edema and enhancement surrounding the left L4 nerve root exiting the neural foramen, as well as the left lumbosacral plexus. Mild edema and mild abnormal enhancement were noted in the left psoas, left iliacus, and left L4/L5 paraspinal muscles. Although the suspected diagnosis was multiple infarcts (affecting vertebral bone and peripheral nerves) and acute denervation muscle atrophy, biopsy was pursued to exclude a malignant or infectious cause (including spinal tuberculosis, given recent travel to Nepal). Biopsy of the L4 vertebral body (Fig. 1c and d) demonstrated viable and nonviable bony spicules consistent with bone infarction, without any evidence of neoplasia or inflammation. Tissue and cerebrospinal fluid mycobacterial cultures were negative. With conservative management, there was marked improvement of pain within 2 weeks. At 1-year follow-up there was only minimal residual weakness in proximal left leg muscles.
a: Axial T1-weighted image shows a serpiginous line with low T1 signal within the vertebral body. There is a decrease in size of the left psoas muscle with a subtle increase in T1 signal compared with right. b: Axial T1-weighted image post-contrast shows serpiginous enhancement within the vertebral body, in keeping with a vertebral infarct. There is enhancement of the left proximal lumbosacral plexus (arrow), in keeping with an acute lumbosacral plexitis. There is diffuse enhancement of the left psoas and iliac muscles, which is suggestive of acute denervation atrophy. c: At low power, the core biopsy shows viable and nonviable bony spicules with focal marrow fat necrosis and occasional hematopoietic elements (magnification ×2, hematoxylin and eosin [H&E] stain). d: At higher power, there are nonviable fragments of lamellar bone with empty lacunae (lacking osteocytes). Along one edge (superior aspect), there is immature woven bone being laid down on top of the nonviable bone (an “osteoid seam”) by osteoblasts, representing bone remodeling in the setting of osteonecrosis (magnification ×20, H&E stain).
DLRPN is an uncommon, proximal, asymmetrical form of diabetic neuropathy with significant morbidity. The clinical presentation is typically one of excruciating unilateral pain in the hip girdle, proximal thigh, or lumbar region. This is followed within days or weeks by significant, predominantly proximal, lower-extremity weakness. In some cases, spread to the contralateral lower extremity occurs within weeks to months. There may be prominent associated weight loss and dysautonomia. In many cases, there is incomplete recovery resulting in lasting neurologic disability.
Initial descriptions of DLPRN emphasized the possibility of vasculopathy relating to diabetic metabolic factors (3). More recent literature, however, favors immune-mediated nerve ischemia resulting from microvasculitis of vasa nervosa at the level of very proximal nerve trunks. The presence of ischemic peripheral nerve damage has been documented in autopsy studies showing infarcts of the lumbosacral plexus and proximal nerve trunks (4). Moreover, biopsy studies of distal sensory nerves have shown regions of patchy inflammation surrounding small-caliber blood vessels, causing nerve ischemia and subsequent axonal loss and focal demyelination (1,5). Similarly, numerous cases of painful focal muscle infarction (diabetic myonecrosis) have been reported in the medical literature, and although the mechanism is not entirely clear, immune-mediated ischemia is felt to play an important role.
This unique case, supported by both radiological and pathological data, highlights the occurrence of ischemic vertebral osteonecrosis concurrent with DLRPN, broadening the spectrum of complications of diabetes. It also lends further support to the role of ischemia in DLRPN. Finally, this case also draws attention to the possibility of diabetic osteonecrosis in the differential diagnosis of suspected malignant or infectious disease of the spine.
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Duality of Interest. No potential conflicts of interest relevant to this article were reported.
Author Contributions. A.B. conceived the study and wrote the initial manuscript draft. T.B.N., B.P., and P.R.B. made significant contributions to drafting subsequent iterations of the manuscript and made critical revisions for important intellectual content. A.B. is the guarantor of this work and, as such, had full access to all the data in this study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
- Received November 14, 2020.
- Accepted December 11, 2020.
- © 2021 by the American Diabetes Association
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