Temporal properties of transcutaneous direct current motor conduction block.

Abstract

Objective. Direct current (DC) electrical block of peripheral nerve conduction shows promise for clinical applications to treat spasticity, pain, and cardiac arrhythmias. Most previous work has used invasive nerve cuffs. Here we investigate the potential of non-invasive transcutaneous DC motor block (tDCB).Approach. In anesthetized rats, force output from the tibialis and peroneus muscles was measured in response to stimulation proximally on the sciatic nerve. DC blocking waveforms were delivered via a surface electrode placed distally on the skin over the common peroneal nerve. The efficacy of the block was observed as the reduction/abolition of muscle force. Experiments using this model were performed with two different electrode types. A range of DC amplitudes and durations were used to elucidate the temporal properties of block.Main results. Higher levels of DC resulted in a larger block percentage. The amount of time needed to induce block depended on the level of DC, with smaller amplitudes resulting in longer induction times. When block was applied for a longer period of time (120s), the block was sustained following DC delivery. This 'recovery period' was longer for higher amplitudes of block. In addition to the block thresholds and temporal effects, two additional evaluations were made: In some animals the efficacy of tDCB to block tetanic muscle contractions was successfully verified. Finally, the effect of tDCB on the stability of nerve conduction was verified using a second distal electrode for comparison.Significance. In this study, tDCB has been shown to reversibly block action potentials in peripheral motor nerves. A subthreshold amplitude applied for a longer duration could produce complete or partial block following a brief induction time. Also, a higher amplitude was associated with a longer recovery time. These temporal properties are important considerations for potential clinical applications.