EEG Routine 5 — Questions and Answers
Question 1: Which montage type records the voltage difference between each electrode and a common average of all electrodes?
- Bipolar longitudinal montage
- Referential montage
- Common average reference montage (Correct answer)
- Laplacian montage
Correct answer: Common average reference montage
The common average reference montage uses the mathematical average of all scalp electrodes as the reference for every channel.
Question 2: A patient falls asleep during a routine EEG. Which feature confirms Stage N2 sleep?
- Alpha attenuation only
- Vertex waves only
- Sleep spindles and K-complexes (Correct answer)
- Delta waves exceeding 50% of the epoch
Correct answer: Sleep spindles and K-complexes
Stage N2 sleep is defined by the presence of sleep spindles (12–14 Hz) and/or K-complexes on the EEG.
Question 3: What is the standard low-frequency filter (LFF) setting used in routine clinical EEG?
- 0.1 Hz
- 1 Hz (Correct answer)
- 5 Hz
- 10 Hz
Correct answer: 1 Hz
A low-frequency filter of 1 Hz (high-pass filter) is the standard setting for routine EEG to reduce slow baseline drift.
Question 4: During a routine EEG, the technologist notes high-amplitude, repetitive muscle artifact obscuring temporal channels. What is the best initial intervention?
- Increase the high-frequency filter to 100 Hz
- Ask the patient to relax the jaw and facial muscles (Correct answer)
- Switch to a bipolar transverse montage
- Increase the sensitivity setting
Correct answer: Ask the patient to relax the jaw and facial muscles
Temporal muscle artifact is best reduced by instructing the patient to relax the jaw and facial muscles to reduce EMG contamination.
Question 5: Which of the following is NOT a standard activation procedure in a routine adult EEG?
- Hyperventilation
- Photic stimulation
- Sleep deprivation prior to recording
- Cold caloric stimulation (Correct answer)
Correct answer: Cold caloric stimulation
Cold caloric stimulation is a vestibular bedside test, not a standard EEG activation procedure; HV, photic stimulation, and sleep deprivation are standard.
Question 6: The alpha rhythm in a normal awake adult typically has a frequency range of:
- 4–7 Hz
- 8–13 Hz (Correct answer)
- 14–30 Hz
- 0.5–3 Hz
Correct answer: 8–13 Hz
The normal adult alpha rhythm ranges from 8 to 13 Hz and is best seen over posterior regions with eyes closed.
Question 7: In a routine EEG report, the term 'breach rhythm' refers to:
- An abnormal spike-and-wave discharge
- Enhanced amplitude and sharpening of rhythms due to a skull defect (Correct answer)
- Generalized slowing from metabolic encephalopathy
- A normal variant seen in children
Correct answer: Enhanced amplitude and sharpening of rhythms due to a skull defect
A breach rhythm is an increase in amplitude and sharpening of EEG activity caused by a focal skull defect reducing attenuation.
EEG Routine 5
Which montage type records the voltage difference between each electrode and a common average of all electrodes?