Artifacts in EEG: How to Recognize and Reduce Common Recording Pitfalls

In EEG, what you see is not always what you get.

One of the most important—and sometimes frustrating—skills for EEG technologists is learning to distinguish true cerebral activity from artifact.

Artifacts can mimic pathological findings, obscure critical data, and lead to misinterpretation if not properly recognized.

Understanding EEG artifacts is not just a technical skill—it is essential for ensuring accurate diagnosis, high-quality recordings, and patient safety.

What Is an EEG Artifact?

An EEG artifact is any signal recorded on the EEG that does not originate from cerebral activity. These signals can come from the patient, the environment, or the equipment itself.

Artifacts are common in nearly every EEG recording. The goal is not to eliminate them entirely—but to recognize, minimize, and document them appropriately.

Why Artifact Recognition Matters

Artifacts can closely resemble abnormal EEG patterns, including:

• Epileptiform discharges

• Rhythmic slowing

• Sharp waves or spikes

Misinterpreting artifact as pathology can lead to:

• Incorrect diagnoses

• Unnecessary treatments

• Missed true abnormalities hidden beneath noise

For EEG technologists, recognizing artifact in real time helps preserve data integrity and supports accurate physician interpretation.

Common Types of EEG Artifacts

1. Movement Artifact

Patient movement—whether intentional or not—is one of the most frequent sources of artifact.

Common causes include:

• Shifting in bed or chair

• Restlessness or discomfort

• Seizure-related motor activity

Movement artifacts often appear as large, irregular waveforms that disrupt multiple channels simultaneously.

2. Muscle (EMG) Artifact

Muscle activity produces fast, low-amplitude signals that can obscure underlying brain rhythms.

Typical sources:

• Jaw clenching

• Tension in the forehead or neck

• Talking or swallowing

EMG artifact is especially prominent in the beta frequency range, making it difficult to assess fast activity accurately.

3. Eye Movement and Blink Artifact

Eye movements generate predictable patterns due to the corneo-retinal dipole.

You may observe:

• Slow rolling eye movements (often during drowsiness)

• Sharp deflections with blinking

• Frontal predominance

These artifacts are normal—but must be recognized to avoid confusion with frontal lobe abnormalities.

4. Electrode Artifact (Pop or Drift)

Poor electrode contact can result in:

• Sudden high-amplitude spikes (“electrode pop”)

• Slow baseline drift

• Intermittent signal loss

These artifacts are often localized to a single electrode or channel and may mimic focal abnormalities.

5. Sweat Artifact

Sweat can alter electrode impedance, leading to slow, rhythmic baseline fluctuations.

Common characteristics:

• Very slow frequency activity

• Often seen in longer recordings

• More prominent in warm environments

6. Environmental and Electrical Artifact

External interference can impact EEG recordings, including:

• 60 Hz electrical noise

• Equipment interference

• Nearby electronic devices

Proper grounding and equipment setup are critical to minimizing these artifacts.

How to Reduce EEG Artifacts

While artifacts cannot be eliminated completely, they can be significantly reduced with good technique and preparation.

Before the Study

• Ensure proper skin preparation and electrode placement

• Achieve low, balanced impedances

• Educate the patient on minimizing movement

During the Study

• Monitor for artifact continuously

• Reposition electrodes or leads as needed

• Encourage relaxation and stillness when appropriate

• Document observed behaviors (movement, talking, etc.)

After the Study

• Clearly annotate artifact events

• Correlate clinical activity with EEG findings

• Communicate concerns to the interpreting physician

Artifact vs. Abnormality: A Critical Skill

One of the most valuable skills an EEG technologist develops is the ability to ask:

“Does this pattern make physiological sense?”

Key questions to consider:

• Is the activity localized or widespread?

• Does it correlate with patient movement or behavior?

• Is it consistent across channels or isolated?

• Does it follow known EEG patterns?

This critical thinking separates artifact from true neurological findings.

The Role of EEG Technologists

EEG technologists are the first line of defense against poor data quality.

By recognizing and managing artifact, you:

• Improve diagnostic accuracy

• Reduce the need for repeat studies

• Support better patient outcomes

• Strengthen collaboration with interpreting physicians

Artifact is not just noise—it is part of the story. And understanding that story is what makes a great technologist.

Final Thoughts

In EEG, clarity is everything.

Artifacts will always be present—but with careful observation, proper technique, and clinical awareness, they do not have to compromise the study.

Because the goal is not just to record brain activity—

It is to understand it.