Abstracts

Rationale: EEG overinterpretation is a common cause of epilepsy misdiagnosis in patients with psychogenic non-epileptic seizures (PNES). Up to 30% of patients with PNES have been previously misdiagnosed with epilepsy given prior EEG interpretations. Errors in the diagnosis of PNES lead to overuse of health care resources, delay in diagnosis, poor outcomes, and patient stigmatization. Methods: We reviewed 20 consecutive patients with PNES admitted to the Epilepsy Monitoring Unit in 2012. All these patients had previous EEGs performed and interpreted by neurologists without formal training in clinical neurophysiology. Previous EEGs were requested and obtained in digital format for review. A board certified neurologist with added qualification in clinical neurophysiology reviewed all EEGs and created a new report. Results: Review of initial EEG reports showed that 11 patients had all EEGs read as normal and 9 patients had at least one EEG read as abnormal with epileptogenic discharges. After review by a clinical neurophysiologist all EEGs (20) were found to be normal. Fifty-five percent of EEGs were misinterpreted. Normal activity reported as abnormal included temporal theta during drowsiness, high voltage vertex waves, wicket spikes, normal phase reversals, and artifacts. Conclusions: The study demonstrates that EEG misinterpretation is very common in patients with PNES leading to erroneous diagnosis of epilepsy in patients with PNES, unnecessary treatment with antiepileptic drugs and delay in making the correct diagnosis and offering the appropriate treatment. These findings suggest that referral of suspected PNES patients for evaluation by a neurologist with qualification in clinical neurophysiology can reduce EEG misinterpretation, and can also contribute to early diagnosis of PNES and improved patient outcomes.