Slowly conducting, low-threshold components of sensory nerve potentials in peripheral neuropathy: A microneurographic study

By recording the averaged potential from a microelectrode inserted into the nerve, small late components of the sensory nerve action potential can be analyzed. We studied the thresholds of the late components in median nerves of 15 normal subjects and 37 patients with peripheral neuropathies. Under normal conditions, the late components reflected the activities of small myelinated fibers which had high thresholds. In the patients with peripheral neuropathies, a part of the late components often had abnormally low thresholds, occasionally the lowest. The presence of low-threshold, late components was related to the pathologies of the different types of neuropathy and correlated with the numbers of regenerating clusters in sural nerve biopsies. These slowly conducting, low-threshold components may originate from regenerating or remyelinating fibers, and therefore should have prognostic value.