Measurement of external pressures generated by nerve cuff electrodes.

When external pressures are applied to a peripheral nerve, tissue damage can occur via compression and blood flow occlusion, resulting in degeneration and demyelination of axons. Although many types of nerve electrodes have been designed to avoid or minimize this pressure during stimulation of the nerve or recording of its activity, the measurement of the pressure exerted by these cuffs has not been reported. Currently, only theoretical models are used to predict nerve cuff electrode pressures. We have developed a nerve cuff electrode pressure sensor to measure external pressures exerted by peripheral nerve cuff electrodes. The sensor has a high sensitivity, linear response with little hysteresis and reproducible output. Pressure measurements have been obtained for split-ring and spiral cuff electrodes. The measurements obtained are in agreement with theoretical predictions. Moreover, they indicate that the pressures exerted by cuffs currently used for stimulation generate only a small amount of pressure, which is below the pressure required to occlude blood flow in nerves. The results also suggest that this new sensor can provide reliable measurement of external pressures exerted by nerve electrodes and would be an important tool for comparing various nerve cuff electrode designs.