Impaired sensory conduction in a mixed nerve induced by high frequency stimulation of the muscle fibres. An experimental study in cats.

To see if symptoms such as sensory disturbance or numbness worsen during exercise as is thought to occur in entrapment neuropathy, we studied the interaction between sensory and muscle nerve fibres in a mixed nerve in cats. Stimulation electrodes were placed on both the deep (muscle) and superficial (sensory) branch of the radial nerve at the elbow. High frequency stimulation at 100 Hz was applied to one branch for five minutes and the nerve action potential of the other branch was recorded at the axilla where the radial nerve is mixed. The stimulation decreased the amplitude of the nerve action potential and prolonged its latency. Recovery from these changes was gradual, and changes were the same whichever branch was stimulated. When a cat's leg was made ischaemic, the changes were more pronounced. The changes in the nerve action potential may have arisen from ischaemia in the nerve, possibly caused by high frequency stimulation.