Equipment Operation & Data Interpretation Flashcards
7 cards from real ABEM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Equipment Operation & Data Interpretation flashcards as text
A patient's median motor NCS shows normal distal latency and CMAP amplitude but the conduction velocity is 35 m/s (normal >49 m/s). This pattern most suggests:
Answer: Diffuse demyelinating polyneuropathy
Diffusely slowed conduction velocity below 75% of the lower limit of normal, with preserved amplitude, suggests a demyelinating polyneuropathy affecting the entire nerve.
Complex repetitive discharges (CRDs) in needle EMG are characterized by:
Answer: Regular, uniform discharges that start and stop abruptly with a 'machine-like' sound
CRDs are high-frequency (5–100 Hz), uniform, repetitive discharges of constant morphology that start and stop abruptly, producing a machine-like sound.
During single-fiber EMG (SFEMG), 'jitter' is defined as:
Answer: The variability in interpotential interval between two muscle fiber action potentials from the same motor unit
Jitter is the variability (MCD – mean consecutive difference) in the time interval between action potentials of two muscle fibers belonging to the same motor unit.
In somatosensory evoked potentials (SSEPs), the N20 component recorded over the scalp following median nerve stimulation represents:
Answer: Thalamo-cortical radiation or primary somatosensory cortex activation
The N20 is the first cortical response generated in or near the primary somatosensory cortex (area 3b) following median nerve stimulation.
When performing near-nerve sensory recording (intraneural technique) compared to surface electrode recording, the primary advantage is:
Answer: Higher amplitude SNAPs enabling detection of small or absent responses
Near-nerve needle recording dramatically increases SNAP amplitude, allowing detection of responses too small to be recorded with surface electrodes.
A myopathic motor unit action potential (MUAP) pattern is characterized by:
Answer: Reduced duration, reduced amplitude, early recruitment with full interference pattern at low force
Myopathic MUAPs are small (low amplitude, short duration) because fewer muscle fibers per motor unit are functional, and early recruitment occurs as more units are needed to generate force.
The sweep speed setting of 10 ms/division on the EMG display is most appropriate for recording:
Answer: Individual MUAP morphology during needle EMG
A sweep speed of 10 ms/division provides adequate time resolution to analyze individual MUAP duration and morphology during needle EMG.