EDT EDX Testing Techniques 3

Question 1

Which finding on needle EMG is characteristic of acute denervation occurring within 1–3 weeks of injury?

Accepted Answer

Fibrillation potentials and positive sharp waves

Answer

Fibrillation potentials and positive sharp waves appear 1–3 weeks after axonal injury as denervated muscle fibers develop spontaneous instability of their resting membrane potential.

Question 2

The F-wave latency is used clinically to evaluate which segment of the peripheral nervous system?

Accepted Answer

Proximal nerve and nerve root segments

Answer

F-waves travel antidromically to the anterior horn cell and back, making their latency sensitive to conduction abnormalities in proximal nerve segments and nerve roots.

Question 3

What technical error is most likely if a CMAP has an initial positive deflection before the main negative peak?

Accepted Answer

The G1 electrode is placed over the tendon rather than the muscle belly

Answer

An initial positive deflection (volume-conducted artifact) occurs when G1 is not placed over the end-plate zone or is off the muscle belly, causing the wavefront to travel toward rather than away from the electrode.

Question 4

During ulnar motor nerve conduction, which muscle is used as the standard recording site?

Accepted Answer

Abductor digiti minimi

Answer

The abductor digiti minimi (ADM) is the standard recording muscle for ulnar motor nerve conduction studies due to its reliable anatomy and consistent innervation.

Question 5

A patient's median sensory SNAP is absent at the wrist but present with near-nerve recording. This most likely indicates:

Accepted Answer

Low-amplitude signal below surface electrode threshold, not true absence

Answer

Near-nerve needle recording is far more sensitive than surface electrodes; a signal present only with near-nerve recording indicates a very low-amplitude potential, not true absence of sensory axons.

(EDT) Electrodiagnostic Technician Certification Practice Test

(EDT) Electrodiagnostic Technician Certification Practice Test

EDT EDX Testing Techniques 3