EEG Electrode Placement and Montages 2

Question 1

In the International 10-20 system, what do the numbers 10 and 20 represent?

Accepted Answer

The percentage of distance between skull landmarks for electrode placement

Answer

The 10-20 system places electrodes at 10% and 20% intervals of the measured distances between standardized skull landmarks (nasion, inion, preauricular points).

Question 2

Which montage type displays the voltage difference between each electrode and a common reference point?

Accepted Answer

Referential montage

Answer

A referential montage shows the potential at each electrode compared to a single common reference (such as linked ears, Cz, or an average reference), allowing direct comparison of amplitudes across channels.

Question 3

In a bipolar longitudinal (anterior-posterior) montage, a phase reversal at C3 indicates:

Accepted Answer

Maximum negativity or positivity at C3

Answer

A phase reversal occurs where adjacent channels sharing an electrode deflect in opposite directions, indicating the electrode at the reversal point has the maximum voltage for that event.

Question 4

The electrode labeled 'Fz' in the 10-20 system is located at:

Accepted Answer

The midline frontal position

Answer

The 'z' designation indicates a midline position. Fz (frontal zero) is the midline frontal electrode positioned at 30% of the nasion-to-inion distance from the nasion.

Question 5

What is the maximum recommended electrode impedance for routine EEG recording according to ACNS guidelines?

Accepted Answer

5 kOhm

Answer

The American Clinical Neurophysiology Society recommends electrode impedances be below 5 kOhm and balanced across all electrodes to optimize signal quality and common-mode rejection.

EEG - Electroencephalography Practice Test

EEG - Electroencephalography Practice Test

EEG Electrode Placement and Montages 2