Microvasculitis in diabetic lumbosacral radiculoplexus neuropathy

Abstract

We present a case of a 60-year-old man with mild type 2 diabetes mellitus and step-wise progression of bilateral lower limb weakness, numbness, and pain over a 1-year period. At the time of evaluation, he used a walker. He had elevated cerebrospinal fluid protein, abnormal cooling and heat-pain thresholds on quantitative sensory testing, and nerve conduction studies/electromyography consistent with bilateral lumbosacral radiculoplexus neuropathies. Because it was not clear whether the disease was still active, a right superficial peroneal nerve biopsy was performed and showed evidence of active axonal degeneration, ischemic injury, and microvasculitis. On the basis of these results, the patient was diagnosed with diabetic lumbosacral radiculoplexus neuropathy and was treated with weekly intravenous methylprednisolone with marked improvement of neurologic symptoms and signs. This case illustrates the typical clinical, electrophysiologic, and pathologic features of diabetic lumbosacral radiculoplexus neuropathy and the utility of nerve biopsy to judge ongoing disease activity.

Figure 1

Superficial peroneal nerve biopsy: Teased fiber preparation (osmium tetrachloride) shows that most fibers are undergoing active axonal degeneration (A). Semithin epoxy sections (methylene blue) show severe loss of myelinated fibers in a multifocal distribution (some fascicles have few remaining fibers whereas others have none) (B). Serial longitudinal paraffin sections show large epineurial perivascular (sheet-like) inflammatory collections on H&E staining (C) that react to a CD45 (leukocyte common antigen) immunostain. These findings demonstrate an active inflammatory neuropathy.

Figure 2

Superficial peroneal nerve biopsy (serial epineurial paraffin sections): The sections show an epineurial vessel that has inflammatory cells involving the vessel wall (on H&E) (A), that immunostain with CD45 (B) and show disruption of muscle wall elements on smooth muscle actin preparation (C). These findings are diagnostic of microvasculitis.