Temporospatial effects on orthodromic sensory potential propagation during ischemia

Sensory potentials recorded at two to four sites along the median nerve during ischemia in normal subjects were analyzed with respect to the effects of conduction distance and duration of ischemia. Latency increased rectilinearly with the squared duration of ischemia in minutes, and the rate of the latency increase along the nerve was a power of the preischemic latency, a measure of conduction distance. This finding indicates a temporospatial slowing of sensory conduction velocity of ischemic nerves. Calculated latencies fitted with measured values within +/- 0.2 msec in 95% of 385 recordings. The compound potential amplitude decreased exponentially with the concomitant increase in temporal dispersion, which was the major cause for the decrease in amplitude during the first 20 minutes of ischemia. The nerve conduction pattern during ischemia may serve as a model for biochemical axon membrane dysfunction, a possible factor in the pathogenesis of toxic-metabolic neuropathies.