EEG Artifact Identification 5 — Questions and Answers
Question 1: A lateral eye movement artifact in a bipolar longitudinal montage will appear with opposite polarity at:
- Fp1 and Fp2
- F7 and F8 (Correct answer)
- T7 and T8
- O1 and O2
Correct answer: F7 and F8
Lateral eye movements produce opposite-polarity deflections at F7 and F8 because the corneal-retinal potential approaches one side and recedes from the other.
Question 2: Which of the following features best distinguishes tremor artifact from a true EEG rhythm?
- Tremor artifact is always frontally predominant
- Tremor artifact has a fixed frequency matching the patient's tremor rate (Correct answer)
- Tremor artifact only appears in referential montages
- Tremor artifact shows phase reversal in bipolar montages
Correct answer: Tremor artifact has a fixed frequency matching the patient's tremor rate
Tremor artifact mirrors the physiological tremor frequency (4–6 Hz for Parkinson's, 8–12 Hz for essential tremor) and correlates with observed limb movement.
Question 3: A technologist uses a short-time constant (high-pass filter increase) to reduce which type of artifact?
- Muscle artifact
- Slow sweat artifact (Correct answer)
- 60 Hz line noise
- Electrode pop
Correct answer: Slow sweat artifact
Increasing the high-pass (low frequency) filter shortens the time constant and attenuates slow, DC-shift sweat artifact.
Question 4: During sleep recording, repetitive, high-amplitude spike-like potentials appearing synchronously with each heartbeat across all leads are best identified as:
- Vertex sharp waves
- Cardiac (EKG) artifact (Correct answer)
- K-complexes
- Frontal arousal rhythms
Correct answer: Cardiac (EKG) artifact
EKG artifact produces spike-like potentials synchronous with the R-wave, often mistaken for epileptiform discharges if the ECG channel is not reviewed.
Question 5: Which montage change is most useful for confirming that a suspected artifact is truly artifactual rather than cerebral?
- Switching from average to Laplacian reference
- Switching between bipolar and referential montages (Correct answer)
- Increasing the sensitivity
- Decreasing the time base
Correct answer: Switching between bipolar and referential montages
True cerebral activity maintains consistent field distributions across montages, while artifacts often appear or disappear inconsistently when the montage is changed.
Question 6: A high-amplitude, sharply contoured discharge that appears only in a single channel and does not violate the "neighbor rule" of field spread is most likely:
- A focal interictal epileptiform discharge
- An electrode artifact (Correct answer)
- A breach rhythm
- A vertex sharp wave
Correct answer: An electrode artifact
True cerebral discharges have plausible electrical fields involving neighboring electrodes, so an isolated single-channel transient without field spread is likely artifactual.
Question 7: Photomyogenic (photomyoclonic) response, which can mimic a photoparoxysmal response, differs in that it:
- Outlasts the stimulus train
- Is frontally predominant muscle artifact time-locked to each flash (Correct answer)
- Consists of generalized spike-wave discharges
- Begins with a posterior predominance
Correct answer: Is frontally predominant muscle artifact time-locked to each flash
Photomyogenic response is a muscle artifact (frontalis/orbicularis) synchronized to each photic flash, whereas photoparoxysmal response is a true cerebral epileptiform discharge that may outlast the stimulus.
EEG Artifact Identification 5
A lateral eye movement artifact in a bipolar longitudinal montage will appear with opposite polarity at: