Abstracts

Rationale: The misdiagnosis of epilepsy is common, and over-read EEGs are a frequent contributor to the wrong diagnosis of epilepsy. By far the most commonly over-read pattern consists of interictal, sharply contoured temporal fluctuations of background or wickets [Benbadis et al]. We present a series of ictal patterns that were misinterpreted as epileptiform and resulted in a misdiagnosis of epilepsy. Methods: We reviewed EEGs that had been misread as epileptiform in patients who were confirmed to have non-epileptic attacks by EEG-video over a 6-month period. We selected those that were patterns other than sharply contoured temporal transients. Results: We identified 6 patients. These were patients referred to our institution for a second opinion. The first patient, BA, the ictal movement artifact was mistaken for a photoconvulsive response. Patient SS had a repetitive artifact at T6 mistaken for an electrographic seizure. The next patient, GH, the high frequency filter was set at 15 (instead of 70) and chewing artifact was misinterpreted as bifrontal sharp waves. The fourth patient, MF, a photo cell or breach rhythm was mistaken for an electrographic seizure. The ictal EMG was mixed with alpha, mistaken for an electrographic seizure, on patient NC. RC, sixth and last patient, the alpha harmonic was mistaken for an electrographic seizure. Conclusions: Various EEG patterns can be tricky and misinterpreted as epileptiform discharges, and most are artifacts. Because of the increased use of prolonged EEG monitoring (ambulatory or EEG-video), several “ictal” artifacts are being misinterpreted seizures.