Positioning of EEG electrodes

according to the international 10-20 electrode placement System

The following longitudinal lines will be divided into10-20-20-20-20-10% segments:

10/20 System
  • From the Nasion to the Inion (longitudinal line).
  • The lateral line from the left ear opening (A1) to the right ear opening (A2) is the centre line from Nasion to Inion.
  • Three segments (10-20-20%) from frontalis and the remaining three segments (10-20-20%) from occipetalis.
  • The EEG electrodes configuration is according to the 10-20% divisions (see illustration).
  • The electrodes are placed on the centre longitudinal line (Nasio-Inion) according to the 10-20% division as well as symmetrically with equal spacing on its both sides.
  • For adults, the spacing between electrodes is approximately between 5 –7 cm.
  • The index of each electrode position correspond to the correct anatomical index.
  • Following this electrode placement scheme will assure repeatability of the measurement.
  • This electrode placement scheme can be simplified by reducing the number of electrodes when the head size is exceptionally small.
  • The two electrode placement Pg1 and Pg2 will be used in special cases (nose –Esophagus) EEG recordings. A special application electrode (nasopharyngeal electrode) will be used in such special cases.

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