The value of ultrasound-guidance of nerves and muscles for patient tolerance and parameters electrodiagnostic studies.

Objective: To assess impact of ultrasound guidance (USG) on patient's perception of nerve conduction studies (NCS). Methods: In this single-center, randomized, sham-controlled, parallel, single-blind trial, we evaluated ultrasound (US) in identifying NCS stimulation site. Consecutive adults (18-80 old) without neuropathy referred for NCS were electronically randomized 1:1 to USG or Sham US. The primary outcome was sensory supramaximal intensity (SSMI) for each site/nerve; motor supramaximal intensity (MSMI), amplitudes, number of non-routine muscle punctured, Visual Analogue Scale (VAS), satisfaction were secondary outcomes. Results: 290 participants were randomized, with 145 in the USG and 144 Sham US groups, respectively. No difference in SSMI, CMAP or SNAP, VAS, satisfaction was recorded. With USG, the median at the elbow and fibular MMSI were lower (p = 0.04; p = 0.02). With normal NCS or overweight and obese subgroups patients had lower median SSMI (p = 0.05/ p = 0.02), higher median and sural SNAP with normal NCS (p = 0.04; p = 0.007) and the sural SNAP for the expert US subgroup (p = 0.02). Conclusions: USG is useful for nerves, that are anatomically variable or in obesity. The sural SNAP gain with US in the normal NCS subgroup could facilitate routine NCS. Significance: In standard NCS the USG does not modify the patient's tolerance.