Artifact Identification Flashcards

A lateral eye movement artifact in a bipolar longitudinal montage will appear with opposite polarity at:

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.

Which of the following features best distinguishes tremor artifact from a true EEG rhythm?

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.

A technologist uses a short-time constant (high-pass filter increase) to reduce which type of artifact?

Answer: Slow sweat artifact

Increasing the high-pass (low frequency) filter shortens the time constant and attenuates slow, DC-shift sweat artifact.

During sleep recording, repetitive, high-amplitude spike-like potentials appearing synchronously with each heartbeat across all leads are best identified as:

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.

Which montage change is most useful for confirming that a suspected artifact is truly artifactual rather than cerebral?

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.

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:

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.

Photomyogenic (photomyoclonic) response, which can mimic a photoparoxysmal response, differs in that it:

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.