What percentage of the vertical measurement of the head (nasion to inion) is Pz from the inion?

In the context of EEG electrode placement, Pz refers to a specific location on the scalp that is identified in relation to the overall head measurement. The nasion is the bridge of the nose, and the inion is the bony bump located at the back of the skull. The measurement from the nasion to the inion represents the vertical dimension of the head.

Pz is positioned in the midline of the scalp, and its location can be determined by measuring a percentage of the distance from the inion up towards the nasion. In this case, Pz is typically located around 30% of the way up from the inion in the direction of the nasion.

Understanding this positioning is critical for tasks like electrode placement, as it ensures that recordings are standardized and comparable across different individuals and studies. This knowledge is essential for sleep technicians who are setting up EEGs or other monitoring equipment, as it directly affects the accuracy and reliability of the data being collected.