An EEG typically uses between 16 and 25 electrodes, which are often referred to as leads.
Understanding EEG Leads (Electrodes)
An electroencephalogram (EEG) is a test that measures the electrical activity in the brain. The term "leads" in this context refers to the points of contact placed on the scalp to detect these electrical signals. These contacts are technically called electrodes.
According to general information about the procedure, "Between 16 and 25 electrodes will be attached to your scalp with a special paste. Or a cap with the electrodes will be used."
This means the number of leads used in a standard clinical EEG can vary within this specific range.
Why the Range?
The number of electrodes used can depend on several factors:
- Clinical Need: Standard clinical EEGs often use 19 to 21 electrodes based on the international 10-20 system. The reference provides a slightly broader range (16-25), which covers common variations.
- Specific Focus: If a neurologist is looking for activity in a particular area, they might use a slightly different configuration or more electrodes for higher density mapping (though high-density EEGs use many more than 25).
- Equipment & Protocol: Different clinics or hospitals might have slightly varying standard protocols and equipment capabilities.
The EEG Procedure: A Quick Look
When undergoing an EEG, you can expect:
- Being asked to relax in a comfortable position, like a reclining chair or bed.
- Application of the electrodes to your scalp using a special paste or by wearing a cap that already has the electrodes embedded.
- Recording brain activity for a period, which might involve asking you to open/close your eyes, breathe deeply, or watch a flashing light.
The electrodes detect the tiny electrical signals produced by your brain and send them to the EEG machine, which records them as wavy lines on a computer screen or paper.
Summary of Typical EEG Leads
| Component | Count | Description |
|---|---|---|
| Leads | Between 16 and 25 | Electrodes placed on the scalp |
| Purpose | Record brain activity | Detect electrical signals from the brain |
In summary, while specialized EEGs can use many more, a standard clinical EEG typically employs between 16 and 25 electrodes or leads to monitor brain function.
