Diabetes Care | 2021
Vertebral Ischemic Necrosis in Diabetic Lumbosacral Radiculoplexus Neuropathy
Abstract
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) grade2/5paresis of the left hipflexor 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–L4myotomes. 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 Figure 1—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 psoasmusclewitha subtle increase in T1 signal compared with right. b: Axial T1weighted image post-contrast shows serpiginousenhancementwithin thevertebral body, in keeping with a vertebral infarct. There is enhancement of the left proximal lumbosacral plexus (arrow), in keeping with an acute lumbosacralplexitis.There isdiffuseenhancement 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 spiculeswith focalmarrow fat necrosis and occasional hematopoietic elements (magnification 32, 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”) byosteoblasts, representing bone remodeling in the setting of osteonecrosis (magnification 320, H&E stain).