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
Which of the following is the correct cathode placement rule for nerve conduction studies?
Answer: Cathode proximal to the anode to avoid hyperpolarization under the anode blocking the impulse
The cathode (negative electrode) must be placed closer to the recording site so the action potential is initiated beneath the cathode and is not blocked by hyperpolarization under the proximal anode.
In blink reflex testing, the R1 response is generated by which pathway?
Answer: Trigeminal afferent → oligosynaptic pontine circuit → ipsilateral facial nerve efferent
R1 is an ipsilateral, early (9–13 ms) response mediated by a short oligosynaptic reflex arc through the pons between the trigeminal and facial nuclei.
Prolonged insertional activity in needle EMG is most commonly associated with:
Answer: Denervated or irritable muscle
Prolonged insertional activity reflects an irritable muscle membrane, most commonly seen in denervation, inflammatory myopathies, or ion channel disorders.
Which nerve conduction parameter is MOST sensitive for detecting early axonal loss neuropathy?
Answer: CMAP or SNAP amplitude
CMAP and SNAP amplitudes reflect the number of conducting axons and decline early in axonal loss, while conduction velocity and latency remain relatively normal until significant axon loss occurs.
Myotonic discharges on needle EMG differ from complex repetitive discharges (CRDs) in that myotonic discharges:
Answer: Wax and wane in amplitude and frequency, producing a 'dive-bomber' sound
Myotonic discharges characteristically wax and wane in both amplitude and frequency, creating the classic 'dive-bomber' or revving motorcycle sound on the audio monitor.
When the low-frequency (high-pass) filter is set too high (e.g., 500 Hz instead of 2 Hz) during sensory NCS, the SNAP will appear:
Answer: Smaller in amplitude and shorter in duration with possible loss of slow components
A high low-frequency filter removes slow, low-frequency components of the SNAP, reducing amplitude and duration and potentially making a borderline response undetectable.
In late response studies, the A-wave (axon reflex) differs from the F-wave because the A-wave:
Answer: Has a constant latency and morphology with submaximal stimulation and represents ephaptic or branching axon activation
A-waves have a fixed latency and waveform that appear at submaximal stimulation, reflecting activation of a branch or ephaptic connection rather than the random retrograde motor neuron firing seen in F-waves.