Sensory and Motor Nerve Conduction Velocities Following Therapeutic Ultrasound

JOHN F. KRAMER

Australian Journal of Physiotherapy 1987 · 10.1016/s0004-9514(14)61232-0

human healthyhealthyemg mep

Abstract

Nineteen healthy volunteers each received six, five-minute ultrasound treatments at sonation intensities of 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 W/cm(2), applied along the proximal forearm segment of the ulnar nerve, over an area of approximately 4.5 times the area of the ultasound application head. Sensory and motor nerve conduction velocities responded similarly, but not identically to ultrasound. All clinical intensities, with the exception of 0.5 W/cm(2) (p <0.10), were associated with significantly increased velocities. Subcutaneous tissue temperatures were directly related to sonation intensity, although significantly increased temperatures were not observed until 1.5 W/cm(2) intensity was used. The effectiveness of clinical applications of ultrasound in pain relief cannot be attributed to a decrease in nerve conduction velocity of the faster conducting A-fibers, which are evaluated using standard nerve conduction techniques.

Abstract via europepmc.

Specieshuman

Subjects19 participants

Sessions per subject6

Randomisedyes

Blindingsingle

Sham / controlinactive transducer

Auditory controlnot reported

Readout timingoffline

Anaesthesianot applicable

Readoutsemg mep — antidromic sensory and orthodromic motor nerve conduction velocity (ulnar nerve, EMG); subcutaneous tissue temperature

Direction of effectexcitatoryAll clinical sonation intensities (0.5-2.5 W/cm2) were associated with significantly increased sensory and motor nerve conduction velocities relative to the 0.0 W/cm2 (placebo) condition; attributed to a heating effect of continuous ultrasound rather than a mechanical/blocking effect.

Adverse eventsnone observedAll subjects completed the full five minute treatments, using each of the six ultrasound intensities. The subjects did, however, report an increasing sensation of heatiñg as the sonation intensity increased — particularly so at sonation intensities of 2.0 and 2.5 W/ $\mathsf { c m } ^ { 2 } .$ Based on the subjects comments, heating ranged from imperceptible to mild, at intensities of 0.0 through 1.5 $\mathbf { W } / \mathbf { c m } ^ { 2 }$ , and from mild to very warm, at 2.5 W/cm². None of the subjects reported the heating at $2 . 5 \ \mathrm { W } / \mathrm { c m } ^ { 2 }$ to be hot or painful — the criteria for discontinuing treatment.

Exposures

Exposure 1: Continuous 870 kHz ultrasound over the ulnar nerve at six intensities (0.0-2.5 W/cm2)

Target: ulnar nerve — “proximal forearm segment of the ulnar nerve”
Device: other named manufacturer · Burdick Corporation · UT/4300

Pulse timing
Waveform	continuous
Fundamental frequency (kHz)	870	✓✓✓
Pulse duration (ms)	not applicable
Pulse repetition frequency (Hz)	not applicable
Duty cycle (%)	not applicable
Sonication duration (s)	300	✓✓✓

Pressure and intensity, by domain
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
Ispta, domain unspecified (W/cm²)	0.5, 1, 1.5, 2, 2.5swept	✓✓✓

Protocol, in the paper’s words

Each of 19 volunteers received six separate five-minute continuous-ultrasound treatments (0.0, 0.5, 1.0, 1.5, 2.0, 2.5 W/cm2, order randomised, >=48 h apart) applied with a moving soundhead (~3 cm/s, ~50% circle overlap) over a 12 cm x 5 cm area of the proximal forearm along the ulnar nerve.

Flags from extraction

exposures[0].unspecified_domain.isppa_w_cm2 — paper reports device-output intensity in W/cm2 without stating whether this is a free-field/water calibration value or an at-skin value, and without naming the intensity metric (ISPPA vs ISATA/ISPTA); placed in unspecified_domain.
blinding — subjects were not told the assigned intensity until after treatment (subject-blind); no statement that the outcome assessor was blinded to intensity (only blinded to pre/post time order), so classified as single rather than double blind.
sham_type — the 0.0 W/cm2 condition (device applied, soundhead moved, gel used, output at zero) is treated as the inactive-transducer sham arm and excluded from the active exposure intensity list.