Relationship between stimulus amplitude, stimulus frequency and neural damage during electrical stimulation of...

The relation is investigated between stimulus frequency, stimulus pulse amplitude and the neural damage induced by continuous stimulation of the cat's sciatic nerve. The chronically implanted electrodes were pulsed continuously and the effects of the electrical stimulation were quantified as the amount of early axonal degeneration (EAD) present in the nerves seven days after the continuous stimulation. The primary effect of stimulating at 100 Hz rather than 50 Hz was to cause an increase in the slope of the plot of the amount of EAD versus stimulus amplitude, but the threshold stimulus for the induction of EAD also was slightly lower. There was a small amount of EAD in three of the nerves stimulated at 20 Hz, but there was no detectable correlation between the amount of EAD and the stimulus amplitude. This suggests that continuous electrical stimulation of peripheral nerves at a low frequency induce little or no neural damage, even if the stimulus amplitude is very high. A preliminary presentation of the results has been made elsewhere (Agnew et al., 1993).