Montage Modification - Neurodiagnostics EEG · © Trusted Neurodiagnostics Academy Circumferential Bipolar © Trusted Neurodiagnostics Academy Laplacian Montage Each electrode is

© Trusted Neurodiagnostics Academy

Montage Modification


Montages

• Montages are systematic and logical combinations of pairs of electrodes which allows for recording of the EEG over the entire scalp.

• Compare homologous parts of the brain to each other


Montages

• ACNS Guidelines

• Minimum of 16 electrodes

• 10-10 or 10-20 electrode utilization

• Can include EKG and EMG


Referential Montages• Multiple electrodes are referenced to a common reference electrode

• Reference electrode is electrically inactive

• Ear reference

• A1/A2 reference

• Cz reference

• Average reference

• Give true amplitude, frequency, and phase of the waveform displayed


Referential Montages• Average Reference Montage

• Combine all electrode’s electrical activity and utilize for the reference.

• Accentuates focal activity

• Used for topographical brain mapping and qEEG

• Disadvantage: one electrode with significant artifact can distort all channels in the average montage.


Referential Montages

• Contamination

• Ear reference

• Cz reference

• Localization of focus is the channel with the highest amplitude not phase reversal.


Referential Montages


Ear Reference


CZ Reference


Bipolar Montages• Congruent pairs of electrodes are referenced to each other

• Longitudinal bipolar

• Transverse bipolar

• Circumferential bipolar

• Useful to locate maximum potentials

• A phase reversal between two channels indicates that the focus is at the common electrode.


Bipolar Montages

Sometimes called “Double Banana”


Bipolar Montages

Double Distance Montage


Longitudinal Bipolar


Transverse Bipolar


Circumferential Bipolar


Laplacian Montage

• Each electrode is referenced to its own unique reference made up of all the adjacent electrodes

- Removes contamination from signals that are distant but would otherwise appear due to volume conduction.

• Focal events are seen in larger amplitude

• Utilized for source localization

• Not used for examining generalized discharges


Laplacian Montage


Montage Modifications

• Digital Systems can reformat the montages after recording

• Modifying Montages

• Limitation on electrodes

• Neonatal specific montages

• Isolate a discharge focus


Montage Modifications• Grid and strip electrodes

• Do not montage together distant electrodes

• Depth electrodes

• Voltage inaccuracies will occur if you montage the first and last inputs on the same depth electrode

Documents

Montage Modification - Neurodiagnostics EEG · © Trusted Neurodiagnostics Academy Circumferential Bipolar © Trusted Neurodiagnostics Academy Laplacian Montage Each electrode is