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Abstract Details

EEG Analysis of Eye Movement Artifact in Parietal and Occipital Lobe Seizures: A Search for Epileptic Nystagmus
Epilepsy/Clinical Neurophysiology (EEG)
P10 - Poster Session 10 (8:00 AM-9:00 AM)

EN is a rarely reported seizure semiology, most commonly associated with seizures originating in the posterior cortical regions. EN is often easily missed in long-term video-EEG (vEEG) recordings because of multiple reasons such as poor camera resolution or camera not focused on the eyes.

To report a method of eye movement artifact analysis on EEG without EOG electrodes, and to identify a characteristic eye movement artifact in parietal and occipital lobe seizures, consistent with Epileptic nystagmus (EN).

We performed a retrospective vEEG analysis of three patients with occipital and parietal lobe seizures. The eyes were not clearly visible in any of the patients. We analyzed 30 seconds of pre-ictal EEG for any unusual eye movements, followed by the ictal EEG. We identified epochs of unilaterally directed repetitive saccadic eye movement artifacts (≥5 saccades) during the ictus. We analyzed these eye movements in a longitudinal bipolar montage with increased time constant (TC) of ≥2 seconds.

In all three patients, there was no specific pattern of repetitive saccadic eye movement artifact in the pre-ictal period. During the ictus, all of the patients showed repetitive contralaterally directed saccadic eye movements. When analyzed with TC≥2 seconds, the saccades were alternating with linear slow phases directed ipsilateral to the seizure focus. In one patient, there was a clear prolonged slow drift ipsilateral to the seizure focus before the onset of nystagmus, consistent with type II EN.

EN is likely under-reported because of either lack of video evidence or lack of special EOG electrodes. Our study demonstrates a specific pattern of eye movement artifact seen on EEG in parietal and occipital seizures, consistent with EN. We also report a method to identify the slow and fast phases of EN on EEG, which can also delineate the underlying mechanism of EN (type I v type II).

Aybuke Acar, MD (University Hospitals Cleveland Medical Center)
Dr. Acar has nothing to disclose.
Anthony Peter Zampino, MD (University Hospitals) Dr. Zampino has nothing to disclose.
Marshall Kirsch, DO Dr. Kirsch has nothing to disclose.
Neel Fotedar, MD (University Hospitals Cleveland Medical Center) Dr. Fotedar has nothing to disclose.