Ultrasound’s Effect on the Conduction Latency of the Superficial Radial Nerve in Man
John S Halle, Charles R Scoville, David G Greathouse
Physical Therapy 1981 · 10.1093/ptj/61.3.345
Abstract
Research has clearly demonstrated that ultrasound has an effect on nervous tissue and its ability to propagate an action potential, but controversy exists concerning what physiological changes occur and whether these changes are due to the thermal or mechanical properties of ultrasound. The purpose of this study was to clarify the effect caused by mechanical and heating factors on sensory nerve conduction by comparing the effects of equivalent temperature changes by a strictly thermal source and by ultrasound. Ten healthy adults were exposed to ultrasound and infrared on separate treatment sessions to create a 1.2 degrees C increase in subcutaneous tissue temperature. Nerve conduction latencies were recorded for each 0.3 degrees C increase during both the ultrasound and infrared treatments. Results were analyzed using a two-way analysis of variance and a matched-group Student's t test. The combined mechanical and heating effects of ultrasound caused a decrease in latency of the lateral cutaneous branch of the radial nerve, similar to that of the heating effects of infrared. The results indicated that ultrasound's mechanical effects did not play a significant role in affecting the nerve conduction latency.
Abstract via europepmc.
Exposures
Exposure 1: Continuous 1 MHz ultrasound to forearm over superficial radial nerve
Target: peripheral nerve — “superficial terminal branch of the radial nerve”
Device: Mettler · Mettler Electronic Corp, Anaheim, CA · Ultrasound Model ME 702
| Waveform | continuous | |
|---|---|---|
| Fundamental frequency (kHz) | 1,000 | ✓✓✓ |
| Pulse duration (ms) | not applicable | |
| Pulse repetition frequency (Hz) | not applicable | |
| Duty cycle (%) | not applicable | |
| Sonication duration (s) | 300, 1,200swept | ✓✓✓⚑ |
| Free-field pressure (kPa) | not reported | |
|---|---|---|
| Free-field Isppa (W/cm²) | not reported | |
| Free-field Ispta (W/cm²) | not reported | |
| In-situ estimate | not reported | |
| In-situ pressure (kPa) | not reported | |
| In-situ Isppa (W/cm²) | not reported | |
| In-situ Ispta (W/cm²) | not reported | |
| Isppa, domain unspecified (W/cm²) | 1 | ✓✓✓ |
| Ispta, domain unspecified (W/cm²) | 1 | ✓✓✓⚑ |
Ultrasound applied in circular motion with a 2-cm sound head until subcutaneous temperature rose 1.2 C, interrupted after each 0.3 C rise to record latency. Treatment lasted 5 to 20 minutes (mean 13.2 minutes). Infrared comparison given in a separate session.
Flags from extraction
exposures[0].unspecified_domain.ispta_w_cm2— 1.0 W/cm2 is a clinical dial intensity; the paper does not say whether it is spatial-peak or spatial-average or temporal-average; placed under ispta as continuous wave.exposures[0].timing.sonication_duration_s— Duration varied with rate of temperature rise; recorded as stated range.exposures[0].target.terms— Peripheral nerve stimulated percutaneously in forearm, not brain.direction_of_effect— Latency fell with heating in both ultrasound and infrared conditions; authors attribute this to heat, not a specific ultrasound effect.sham_type— Infrared heating was used as a comparison modality; there was no sham ultrasound.