Sural nerve lesions in 5 male diabetic patients with clinically manifest diabetic neuropathy were investigated by electron microscopy. Axonal degeneration of both myelinated and unmyelinated nerve fi bers was apparent in all cases. Also found were destruction of myelin sheaths, degenerative changes in Schwann cell cytoplasm, and thickening and multiplication of the basement membrane of the vasa nervorum in all subjects. In addition to depletion of axoplasmic organelles, the axonal degeneration appeared as vacuolation and reduction of the axon diameter, accumulation of glycogen-like particles and deposition of electron-homogeneous amorphous materials. On the other hand, the formation of degenerated myelin debris, various kinds of cytoplasmic inclusion bodies and aggregated glycogen particles were noted in Schwann cells. Basement membrane hyperplasia of Schwann cells with ruffled elongation was also eminent in all the diabetic patients. An increasese in collagen fibers of the interstitium and onion bulb formation were apparent as chronic non-specific alterations of the nerve tissues. There was no apparent correlation between the ultrastructural findings and clinical symptoms or laboratory findings in the patients.
Based on these observations it is concluded that the peripheral nerve lesions in the diabetics developed through metabolic impairment of axons, with accompanying disturbance of Schwann cell metabolism and diabetic microangiopathy in the nerve tissues.