2026 Workshop Handout Bundle-W21RF - NCS Pitfalls

W21RF - NCS Pitfalls - Bassam

Pdf Summary

The workshop reviews common nerve conduction study (NCS) pitfalls that can mimic nerve disease and lead to incorrect diagnoses. These errors may arise from equipment settings, electrode placement or instability, stimulation technique, measurement methods, anatomical variants, and patient physiology.<br /><br />Amplifier sensitivity, sweep speed, and filters must be appropriate and consistent. Incorrect settings can distort waveform amplitude, duration, and latency. Recording electrodes must be correctly positioned and secured: misplaced electrodes can reduce response amplitude or alter waveform shape, while movement can create artifacts, especially during repetitive stimulation. Stimulus artifact can obscure responses and may be reduced through careful skin preparation, ground-electrode placement, and appropriate electrode positioning.<br /><br />Stimulation should be strong enough to activate all relevant nerve fibers, but excessive intensity can spread to nearby nerves and produce misleading responses. Reversing the cathode and anode can delay measured latency and falsely suggest distal nerve disease. Accurate distance and latency measurements are essential; short distances magnify measurement error. Sensory response amplitudes may also decline substantially with stimulation farther from the recording site, making comparisons across sites unreliable.<br /><br />Anatomical variants, including Martin–Gruber anastomosis and accessory deep peroneal innervation, can imitate conduction block or other abnormalities. Interpretation must account for age, temperature, and potentially other individual factors. Cool limbs can prolong latencies, slow conduction, and alter response amplitudes; temperature should be measured at the limb and controlled, particularly during repetitive stimulation. H-reflexes may require facilitation before being considered absent.<br /><br />The central recommendation is to recognize and correct technical and physiological sources of error, reproduce the methods used to establish reference values, and interpret findings in clinical context. Doing so improves the accuracy of electrodiagnostic studies and reduces false-positive and false-negative conclusions.

Keywords

nerve conduction study

ncs

ncv

electrodiagnostic errors

waveform artifacts

electrode placement

stimulation technique

amplifier settings

anatomical variants

conduction block

limb temperature

false diagnosis