An ultrastructural study of chronic sodium cyanate-indiuced neuropathy.

Fifteen rats were given a sodium cyanate-rich diet for 18 months and at the end of that period, all of them had developed motor weakness and were perfused for ultrastructural study. A peripheral neuropathy involving mostly the roots and sciatic nerves was found and the main ultrastructural lesion was vacuolization of myelin. There was marked distinction of the myelin sheaths and phagocytosis of myelin. Axoplasmic changes were minimal and consisted of accumulation of glycogen within vacuoles. Invaginations of adaxonal Schwann cell membranes and axolemma forming loops and separate chambers were also present. There was active participation of macrophages in the splitting of myelin as well as in phagocytosis of myelin remnants. There was evidence of remyelination with the toxic damage. We concluded that cyanate induced neuropathy is due mostly to a myelinotoxic effect of the drug, although parallel but less intense axonal damage cannot be excluded.