Peripheral Nerve Conduction Block by High-Frequency Alternating Currents: A Systematic Review.

Numerous neurological dysfunctions are accompanied by an undesirable increase of nerve activity, such as neuropathic pain or spasticity. There have been several studies over the last years on peripheral nerve block using high-frequency alternating currents, which could become a therapeutic alternative for such nerve hyperactivity. The main aim of this systematic review was to determine the optimal parameters of the electrical currents for producing peripheral nerve conduction block, the underlying neurophysiological mechanisms, and their possible adverse effects. Of the 49 included studies, 30 were animal experiments, 13 were computer simulations, and six were clinical trials. High-frequency alternating currents using frequencies of >4-5 kHz effectively block nerve conduction. However, depending on the type of axon or nerve diameter, the minimum frequency required to produce the nerve block could be >20kHz. Electrodes design, electrode-axon distance, and temperature are variables that affect the block threshold. There is no consensus about the block mechanism, although it has been showed that the frequency is a key factor to produce K+ channels activation or Na+ channels inactivation. The nerve block produced by currents quickly reverts without causing further damage to the nerve. Studies in humans are necessary to further validate what preclinical studies have already shown.