Introduction

The 10-20 System is an internationally recognized method for placing electrodes on the scalp during electroencephalography (EEG) recordings. It is designed to ensure consistency and reproducibility of electrode positioning across patients, enabling accurate comparisons and analysis of brain activity.

Basic Concepts

  • Electrodes: Sensors placed on the scalp to detect electrical activity generated by neurons in the brain.
  • Standardization: The 10-20 System divides the head into regions based on fixed distances between anatomical landmarks.
  • Units of Measurement: The "10" and "20" refer to the percentage distances between electrodes, measured relative to the total length of the head.

Step-by-Step Explanation of the 10-20 System

Step 1: Identifying Landmarks

The first step is to locate key anatomical landmarks:

  • Nasion: The indentation between the forehead and the nose bridge.
  • Inion: The prominent bump at the back of the skull.
  • Preauricular Points: The indentations just above the ear canals.

Step 2: Measuring Head Circumference

Using a flexible measuring tape, measure the head's circumference by connecting the nasion, inion, and preauricular points in a circular manner. This measurement helps establish electrode spacing.

Step 3: Determining Electrode Placement

Divide the head into regions based on the following percentage distances:

  • 10% from the nasion to the first electrode.
  • 20% intervals between subsequent electrodes.
  • 10% from the last electrode to the inion.

This applies to both longitudinal (front-to-back) and transverse (side-to-side) measurements.

Step 4: Assigning Electrode Labels

Each electrode is labeled based on its location:

  • Fp (Frontal Pole): Near the forehead.
  • F (Frontal), C (Central), P (Parietal), T (Temporal), O (Occipital): Regions across the head.
  • Even numbers (e.g., F4, C4): Right hemisphere.
  • Odd numbers (e.g., F3, C3): Left hemisphere.
  • Z (Zero): Midline electrodes (e.g., Cz, Pz).

Advanced Insights

  • Clinical Applications: The 10-20 System is used in diagnosing epilepsy, sleep disorders, and brain injuries.
  • Extended Systems: Advanced configurations, such as the 10-10 or 10-5 systems, increase spatial resolution for research and specialized applications.
  • Challenges: Accurate placement requires skill and training to avoid errors that could compromise data quality.

Conclusion

The 10-20 System is a foundational framework for EEG electrode placement. Its systematic approach ensures consistency and accuracy, enabling healthcare professionals and researchers to analyze brain activity effectively.