Study of the evolution of nerve damage in leprosy. Part I--Lesions of the index branch of the radial cutaneous nerve in early leprosy.

A total of six index finger branch of the radial cutaneous (IRC) nerves from three BL, two BB and one BT cases of leprosy, with less than 6 months history of disease were subjected for nerve conduction velocity (NCV) studies followed by biopsy. The biopsy was divided into three parts and subjected for light microscopy quantitative histology, electron-microscopy and fibre tease studies. The nerves revealed a slight reduction in NCV and a varying degree of segmental demyelination ranging from 10% to 35%. The earliest changes observed were the thickening and proliferation of Schwann cell processes of the unmyelinated fibres and degeneration of their axons regardless of the type of leprosy.