Can neuralgias arise from minor demyelination? Spontaneous firing, mechanosensitivity, and afterdischarge from conducting axons

Mammalian peripheral axons respond to local disruption of their myelin sheath with membrane changes which support continuous conduction of the impulse through the affected region. We report here that sites of demyelination may become foci of spontaneous impulse initiation. Such sites may also generate ectopic discharges upon slow mechanical distortion. Finally, conduction of an impulse train through a demyelinated region may set off an ectopic afterdischarge that may last many seconds. Rhythmic ectopic firing in dysmyelinated but conducting axons is very similar to that observed in regenerating axons and nerve-end neuromas. Although the latter have long been recognized as sources of pathophysiologic sensations, this is the first indication that neuralgias could arise following minor dysmyelination in peripheral nerves without substantial conduction deficits.