Eye Blinks

Eye blinks are among the most common artifacts observed in EEG (electroencephalography) recordings. These artifacts are characterized by high amplitude negative waveforms, typically found in the bifrontal regions of the scalp, particularly in the Fp1 and Fp2 electrodes. The primary cause of these blinks is Bell's Phenomenon, which is a natural physiological response that occurs when a person blinks their eyes.

During a blink, the eyes' cornea (which carries a positive charge) and retina (which is negatively charged) move relative to each other. As the eye rolls upward slightly during the blink, the cornea moves closer to the frontal electrodes (Fp1 and Fp2), creating a change in the electric field that results in a positive signal. This is why eye blinks produce a noticeable wave in the EEG, especially in the frontal regions.

It is important to note that eye blinks are generally confined to the frontal leads of the EEG and should not extend into the posterior regions. The pattern associated with eye blinking is similar to that seen during eye closure. Upon opening the eyes, a reversed waveform appears, with a large bifrontal negative charge. This is a normal response and does not indicate a pathology in the brain.

While eye blinks are a normal part of an awake EEG, it is crucial to differentiate them from other potential artifacts or abnormal EEG patterns. For instance, frontal spike and waves, or anterior predominant generalized spike and waves, may appear similar but have different clinical significance. Eye blinks, on the other hand, are typically not associated with underlying neurological conditions and are usually benign.

Key Takeaways:

  • Eye blinks produce high amplitude negative waveforms in the frontal leads (Fp1 and Fp2).
  • The phenomenon is a result of Bell's Phenomenon, involving the cornea's positive charge and the retina's negative charge.
  • Eye blinks should not extend into posterior regions of the EEG.
  • Similar waveforms appear during eye closure, with an opposite waveform when the eyes open.
  • Be cautious not to confuse eye blinks with frontal spike and wave patterns, which could suggest a neurological issue.

Understanding these patterns is essential for accurate EEG interpretation, especially when analyzing normal, awake EEG recordings.