Diabetic lumbosacral radiculoplexus neuropathy in an older patient

A 79-year-old man with type-2 diabetes, treated with metformin, presented with significant weight loss and marked pain and weakness in the left thigh persisting for 3 months, thus, requiring him to use a cane. The pain arose from his lower back and radiated into the anterior thigh. The left lower limb showed patellar areflexia and weakness in the psoas, quadriceps, and buttocks muscles. Significant left quadricipital amyotrophy was identified (Fig. 1A). Sensitivity was preserved. Neurological examination of the other limbs was normal. Cranial nerves were intact. HbA1c was 10.1%; other laboratory findings were unremarkable. Antibodies to extractible nuclear antigens, rheumatoid factor, and Lyme serology were negative. Magnetic resonance imaging of the lumbosacral plexus was normal, showing no compressive mass, and that of the thoracolumbar spine was reassuring. Computed tomography of the thigh confirmed reduced muscle trophicity (Fig. 1B). Electromyography showed peripheral denervation from L1–L4, with reduced recruitment in the left thigh myotomas without abnormal rest activity. Cerebrospinal fluid showed an increased protein rate of 0.86 g/L (nL < 0.45), without nucleated cells. The poorly-controlled diabetes, electromyographic results, absence of nerve root compressive signs, and lumbar puncture results led to a diagnostic assumption of diabetic lumbosacral radiculoplexus neuropathy (DLSRPN). Oral methylprednisolone 64 mg/day, with reduced-dose regimen, was started, and insulin therapy replaced the metformin. Improvement was noted within days, with marked reduction in disability. Follow-up confirmed this finding and the amyotrophy