Abnormal spontaneous activity in single sensory nerve fibers in humans.

Spontaneous discharges generated in human motor nerve fibers have long been recognized, and their effects have been comfortably recorded from the muscle target with needle electrodes. Delay in documenting comparable phenomena from sensory fibers is explained by the need to record the abnormal activity directly from nerve fibers using intraneural microelectrodes. The hypothesis that a variety of positive sensory phenomena associated with nerve disease is the result of ectopic impulse generation from within the sensory unit can now be tested with microneurographic techniques. Research inaugurating microneurography in the study of positive sensory phenomena has yielded evidence of ectopic impulse generation from sensory units in subjects actually experiencing paresthesia or pain. The phenomenology of ectopic discharges in sensory fibers has been recorded with intraneural microelectrodes in: (1) transient postischemic paresthesia induced experimentally in otherwise normal nerves; (2) spontaneous paresthesia symptomatic to (probable) structural nerve pathology; and (3) in the sign of Tinel in traumatic neuromas.