Peripheral neuropathy following intraneural injection of mercury compounds

Between 0.25-25 micrograms of an aqueous solution of either mercuric chloride or methyl mercuric acetate was injected directly into the sciatic nerve of 28 adult Wistar rats. The resultant pathological changes in the nerve were examined by teasing individual fibres and by light and electron microscopy. In most respects mercuric chloride was more toxic than methyl mercuric acetate. The large doses of mercuric chloride produced a hind limb paresis within 24 h but no clinical signs followed injection of organic mercury. The predominant effect of mercuric chloride was on Schwann cells which showed cytoplasmic swelling and necrosis, associated with extensive segmental demyelination. In contrast methyl mercuric acetate caused axonal degeneration in many of the large myelinated fibres but only minor alterations were observed in Schwann cells.