Non-epileptic seizures: delayed diagnosis in patients presenting with electroencephalographic (EEG) or clinical signs of epileptic seizures

The clinical differentiation between epileptic seizures (ES) and non-epileptic seizures (NES) is often difficult and mostly based on the presence or absence of widely recognized features of ES such as tongue biting, falling, incontinence or concomitant epileptic abnormalities in the electroencephalogram (EEG). We retrospectively analysed the records of all patients referred to our Epilepsy Centre for refractory epilepsy and finally diagnosed with NES between 1980 and 1999 ( n= 103), half of them also exhibiting ES. The mean time-lapse between first attack and NES diagnosis was 8.7 +/- 1.3 years and 16.5 +/- 1.4 years for the NES and NES + ES groups respectively. At least one of the usual signs associated with generalized tonic-clonic seizures (tongue biting, falling or incontinence) was reported by 66% and 60% of patients with NES or NES + ES respectively. Interictal EEG abnormalities were recorded in 16% of NES patients vs. 80% of NES + ES patients. In the NES group, delay before establishing the correct diagnosis was significantly longer when the patients exhibited > or =1 symptom(s) of generalized seizures, or when patients exhibited interictal EEG abnormalities. Upon admission, 72% of NES patients and all NES + ES patients were being treated with antiepileptic drugs (AEDs).We conclude that EEG or clinical abnormalities suggestive of epileptic seizures are common in undiagnosed NES patients. Such diagnostic pitfalls, besides considerably delaying NES diagnosis, also considerably delay appropriate treatment implementation.