The reasons for misinterpretation are unclear and complex.

13 Conservative reading of EEGs is important in avoiding misdiagnosis, which wastes society’s and the patient’s healthcare resources and delays proper treatment. 12 Unfortunately, the longer the delay in arriving at the diagnosis of PNES, the worse the prognosis. Acceptance of the diagnosis of PNES is difficult when patients have been told that their previous EEG was ‘abnormal.’ This may contribute to the usual delay in diagnosis of PNES of seven years. No amount of normal EEGs can undo an abnormal EEG unless this is done, and it is often difficult in clinical practice. It requires obtaining the original EEG and reinterpreting it. Once a patient is ‘labeled’ with a diagnosis, it is difficult to undo it.

First, it may delay arriving at the correct diagnosis.

The consequences of misreading EEGs are many. Other patterns in the studies included wicket spikes, hyperventilation-induced slowing, and hypnagogic hypersynchrony. 9 When the studies were obtained and reviewed carefully, most of the misread patterns were simple fluctuations of sharply contoured background rhythms or fragmented alpha activity. 9–11 One-third of the patients later found to have PNES have had previous EEGs that were interpreted as epileptiform that contributed to the misdiagnosis. Multiple papers have revealed that many patients with non-epileptic disorders such as syncope and PNES have the incorrect diagnosis of epilepsy perpetuated by the misreading of benign EEG patterns. Accuracy in reading EEGs is critical in both identifying patients who have an increased risk of having epilepsy and avoiding the misdiagnosis of epilepsy in patients without epilepsy. 8 These are widely recognized today as non-epileptogenic. 6,7 Studies from the early years of EEG showed higher percentages, usually around 2–4%, because they included 6 and 14Hz positive spikes or six-persecond waves as epileptiform. 4,5 In adults, the percentage is much lower, probably less than 2%. In children, up to 6.8% will have true epileptiform discharges without clinical epilepsy when photic stimulation is used. 2,3 The electroencephalogram (EEG) can be both helpful and misleading in diagnosis. 1 Likewise, in pediatric epilepsy centers, 15–39% have non-epileptic paroxysmal events. Studies in tertiary epilepsy centers have shown that 30% of adult patients referred for intractable ‘epilepsy’ have non-epileptic events, chiefly psychogenic non-epileptic spells (PNES). The accurate diagnosis of epilepsy is difficult.

Eeg normal vs epilepsy