Electroencephalography (EEG) in the Operating Room Flashcards

What is the standard electrode placement system used for intraoperative EEG monitoring?

Answer: 10-20 International System

The 10-20 International System is the universally accepted standard for scalp electrode placement in both routine and intraoperative EEG.

Which EEG frequency band is typically dominant during relaxed wakefulness with eyes closed?

Answer: Alpha (8–13 Hz)

Alpha rhythm (8–13 Hz) is the dominant posterior rhythm during relaxed wakefulness with eyes closed, and is attenuated by eye opening or mental effort.

What type of EEG montage references each electrode to the mathematical average of all scalp electrodes?

Answer: Common average reference montage

The common average reference montage subtracts the mean signal of all scalp electrodes from each individual channel, minimizing bias from any single reference site.

Which filter setting is MOST appropriate for eliminating 60 Hz power line interference in intraoperative EEG?

Answer: Notch filter at 60 Hz

A 60 Hz notch filter selectively removes power line artifact while preserving all clinically relevant EEG frequency bands.

What electrode impedance level is considered acceptable for reliable intraoperative EEG recording?

Answer: Less than 5 kΩ

Electrode impedances below 5 kΩ ensure good electrical contact, minimizing artifact and maintaining signal integrity in the OR environment.

What does increasing the 'sensitivity' setting on an EEG machine accomplish?

Answer: It enlarges the displayed waveforms by decreasing the µV/mm value

Decreasing the µV/mm value (increasing sensitivity) makes waveforms appear taller on the display, useful for visualizing low-amplitude EEG activity.

In intraoperative EEG, a bipolar montage differs from a referential montage in that it:

Answer: Compares adjacent electrodes to one another in a chain

A bipolar montage records the voltage difference between pairs of adjacent electrodes, forming a chain that helps localize focal abnormalities.