EDT EDT Quality Assurance & Documentation 2

Question 1

When a patient's CMAP or SNAP amplitude is unexpectedly low, the first technical factor to assess is:

Accepted Answer

Whether the recording electrodes have adequate skin contact and low impedance

Answer

High electrode impedance due to poor skin contact is one of the most common technical causes of reduced CMAP or SNAP amplitude and should be checked before concluding pathology.

Question 2

Stimulus artifact in NCS is best minimized by:

Accepted Answer

Ensuring the ground electrode is placed between the stimulator and recording electrodes

Answer

Placing the ground electrode between the stimulator and recording electrodes provides a current path to ground that reduces stimulus artifact contaminating the recording.

Question 3

60 Hz power line interference on the EMG tracing is best eliminated by:

Accepted Answer

Optimizing skin preparation, reducing electrode impedance, and ensuring proper grounding

Answer

60 Hz interference is primarily caused by high electrode impedance; good skin preparation (abrasion and cleaning) and proper ground electrode placement reduce this artifact.

Question 4

The recommended stimulation rate for standard nerve conduction studies is:

Accepted Answer

1–3 Hz

Answer

Stimulation at 1–3 Hz allows sufficient recovery time between stimuli to prevent rate-dependent changes in CMAP or SNAP amplitude.

Question 5

Why is supramaximal stimulation required for accurate nerve conduction studies?

Accepted Answer

To ensure all axons in the nerve are activated, producing a maximal and reproducible evoked potential

Answer

Supramaximal stimulation (typically 20–30% above the level that produces maximal response) ensures all axons are activated, making amplitude and velocity measurements reliable.

(EDT) Electrodiagnostic Technician Certification Practice Test

(EDT) Electrodiagnostic Technician Certification Practice Test

EDT EDT Quality Assurance & Documentation 2