Focused Ultrasound Effects on Nerve Action Potential in vitro

Abstract

Minimally invasive applications of thermal and mechanical energy to selective areas of the human anatomy have led to significant advances in treatment of and recovery from typical surgical interventions. Image-guided focused ultrasound allows energy to be deposited deep into the tissue, completely noninvasively. There has long been interest in using this focal energy delivery to block nerve conduction for pain control and local anesthesia. In this study, we have performed an in vitro study to further extend our knowledge of this potential clinical application. The sciatic nerves from the bullfrog (Rana catesbeiana) were subjected to focused ultrasound (at frequencies of 0.661MHz and 1.986MHz) and to heated Ringer’s solution. The nerve action potential was shown to decrease in the experiments and correlated with temperature elevation measured in the nerve. The action potential recovered either completely, partially, or not at all, depending on the parameters of the ultrasound exposure. The reduction of the baseline nerve temperature by circulating cooling fluid through the sonication chamber did not prevent the collapse of the nerve action potential; but higher power was required to induce the same endpoint as without cooling. These results indicate that a thermal mechanism of focused ultrasound can be used to block nerve conduction, either temporarily or permanently.

High-intensity focused ultrasound: past, present, and future in neurosurgery

“…15,25,26,70,86 Other studies have demonstrated activation of neural tissue, both peripherally and in the CNS. 32,50,81 These effects have been postulated to occur as a result of mechanical stimuli (reversible) and thermal ablation (potentially irreversible).…”

A 32-Channel Low-Intensity Focused Ultrasound Stimulator Using Phased Array Miniature Transducers for Enhanced Targeting Accuracy in Neuromuscular Rehabilitation System

“…In conventional FUS stimulation systems, a single FUS transducer with a fixed focus is used. (15)(16)(17)(18)(19) In this configuration, the transducer must be geometrically shifted for the planar control of the focal point. In addition, it is difficult to finely adjust a depth of focus (DOF) because it is only discretely controllable by replacing the transducer.…”

MRI-guided focused ultrasound surgery in musculoskeletal diseases: the hot topics

“…Pulsed FUS can stimulate the receptor and conductive nerve structures of humans and animals as well as the neurons of the central nervous system of invertebrates. 135 Colucci et al 136 more recently studied the application of FUS on sciatic nerves in bullfrogs. The nerve action potential was shown to decrease in the experiments and correlated with temperature elevation measured in the nerve.…”

“…These results indicate that a thermal mechanism of FUS can be used to block nerve conduction, either temporarily or permanently. 136 Foley et al 137 investigated the effects of various exposures (intensity, duration) of HIFU on sciatic nerve conduction in rats, with the aim to identify HIFU exposures that produce biological effects ranging from partial to complete conduction block, indicating potential use of HIFU as an alternative to current clinical methods of inducing nerve conduction block. 137 HIFU was demonstrated to attenuate neural responses of sciatic nerves isolated from normal or neuropathic rats, with diabetic nerves being less suppressed by HIFU and more vulnerable to permanent damage.…”