ABEM Equipment Operation & Data Interpretation 2

Question 1

What is the primary purpose of a notch filter set at 60 Hz in EMG/NCS equipment?

Accepted Answer

Eliminate electrical interference from AC power lines

Answer

A 60 Hz notch filter selectively attenuates electrical noise introduced by AC power line interference without significantly affecting the biological signal.

Question 2

When performing nerve conduction studies, a 'stimulus artifact' that obscures the early response is best reduced by:

Accepted Answer

Reducing the distance between stimulating cathode and anode

Answer

Increasing the distance between cathode and anode reduces the voltage gradient at the recording electrodes, minimizing stimulus artifact.

Question 3

In needle EMG, the term 'insertional activity' refers to:

Accepted Answer

Electrical activity generated by mechanical displacement of muscle fibers during needle movement

Answer

Insertional activity is the brief burst of electrical potentials produced when the needle mechanically depolarizes muscle fibers during insertion or movement.

Question 4

The impedance of recording electrodes should ideally be kept below what value to ensure signal quality in electrodiagnostic studies?

Accepted Answer

5,000 ohms (5 kΩ)

Answer

Electrode impedance should be kept below 5 kΩ (with matched impedances between electrodes) to maximize signal-to-noise ratio and minimize artifact.

Question 5

A nerve conduction study shows a prolonged distal latency with normal conduction velocity in the proximal segment. This pattern is most consistent with:

Accepted Answer

Focal demyelination at or near the distal recording site

Answer

Focal demyelination at the distal segment slows conduction specifically there, prolonging distal latency while leaving proximal velocity intact.

(ABEM) American Board of Electrodiagnostic Medicine Practice Test

(ABEM) American Board of Electrodiagnostic Medicine Practice Test

ABEM Equipment Operation & Data Interpretation 2