A micro-electrode study of peripheral neuropathy in man. Part 1. Responses to single graded stimuli.

Multi-unit micro-electrode recording were obtained from sensory fascicles of the sural and median nerves of 12 control subjects and of 28 patients with peripheral neuropathy. Spontaneous activity and mass responses to mechanical and electrical stimuli were examined. Mechanoreceptor function appeared normal but there was a reduced number of responsive receptors in peripheral neuropathy. The electrical activation threshold of nerve fibres of all conduction velocities was increased in neuropathy and a greater number of fibres needed to be activated for preception to occur. Clinical sensory impairment was associated with a reduction in size of the initial compound action potential of the maximal evoked neurogram and with dispersion of fibre responses. Pathological slowing of fibre conduction velocity was demonstrated in demyelinating neuropathy but in most cases of axomal degeneration the changes in velocity could have been due either to a reduced number of fast conducting fibres, or to conduction block. No changes were observed in C-fibre activity in these patients.