Myelinated nerve conduction studies

However, these results contradict long-accepted in vitro studies on mammalian peripheral nerve fiber axon diameter. These studies suggest that larger myelinated A fibers which conduct with higher velocity may be more susceptible to peripheral nerve blockade with local anesthetics than smaller unmyehnated C fibers which conduct more slowly [12,13]. Jaffe and Rowe in 1996 [14] actually found no difference in sensitivity to lidocaine based on axon diameter. Many mechanisms in addition to axon diameter have been proposed for lidocaine s differential neural blockade, such as differences in Na channel block (state-de-pendent vs. frequency-dependent) between different nerve fiber types. Further research is needed to elucidate the underlying mechanism as well as the discrepancy between the differential blockade witnessed in epidural and peripheral nerve blocks. 

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