Normal variants and artifacts: Importance in EEG interpretation.

Area of Science:

• Neurology
• Neurophysiology
• Diagnostic Imaging

Background:

• Overinterpretation of electroencephalogram (EEG) findings contributes to epilepsy misdiagnosis.
• Accurate EEG interpretation requires distinguishing abnormal epileptiform discharges from normal variants and artifacts.
• The International League Against Epilepsy (ILAE) curriculum emphasizes understanding normal EEG patterns.

Purpose of the Study:

• To educate clinicians on recognizing artifacts and normal EEG patterns that can be misinterpreted as abnormal.
• To improve the diagnostic value and specificity of EEG in epilepsy evaluation.
• To reduce the overinterpretation and misdiagnosis of epilepsy.

Main Methods:

• Review of literature on EEG artifacts, normal rhythms, and normal variants.
• Categorization of artifacts into physiologic (EMG, eye movements, EKG) and extraphysiologic (environmental, device-related).
• Description of normal awake and sleep EEG patterns, including variants with uncertain clinical significance.

Main Results:

• Artifacts are potentials generated outside the brain, categorized as physiologic or extraphysiologic.
• Normal awake patterns include alpha rhythm, mu rhythm, and lambda waves; sleep patterns include POSTS, vertex waves, and spindles.
• Normal variants like wicket spikes and rhythmic midtemporal theta can be mistaken for epileptiform activity.

Conclusions:

• Correct identification of artifacts and normal EEG patterns is essential to avoid overinterpretation.
• Distinguishing normal EEG findings from abnormal ones enhances diagnostic accuracy and specificity.
• This educational review aids in achieving ILAE curriculum learning objectives for epilepsy diagnosis.