Abstracts

Rationale: The over-interpretation of EEGs is common and is an important contributor to the misdiagnosis of epilepsy. We reviewed our experience in order to clarify which EEG patterns are commonly over-read as epileptiform.Methods: We identified patients who were seen at our epilepsy clinic and were ultimately diagnosed with conditions other than epilepsy. We selected those who had previously had an EEG read as showing epileptiform discharges, and whose EEG was available for our own re-review.Results: A total of 37 patients met the above criteria. Eventual diagnoses were psychogenic nonepileptic seizures in 10, syncope in 7, other miscellaneous diagnoses in 5 (TIA, dementia, presyncope, migraine, hypnic jerks), and 15 unexplained nonspecific symptoms. None of the EEGs had epileptiform discharges. The descriptions of the abnormalities included 'temporal sharp waves' in 30, 'frontal sharp waves' in 2, and 'generalized spike-wave complexes' in 2. Three had no reports available to identify the alleged abnormality. The benign patterns mistaken for temporal (30) and frontal (2) sharp waves were simple fluctuations of background activity with anterior or midtemporal phase reversals [see figure]. Some meet criteria for wicket spikes. The 2 benign patterns mistaken for generalized spike-wave complexes were non-specific intermittent rhythmic slowing (“FIRDA”) related to hyperventilation.Conclusions: By far the most common pattern over-read as epileptiform are non-specific fluctuations of background in the temporal regions (or wicket spikes) misread as temporal sharp waves.