Purpose: To examine interictal EEG abnormalities in patients with psychogenic nonepileptic seizures (PNESs).
Methods: (a) Retrospective study of EEG reports of 187 consecutive patients with PNES seen at the Department of Epileptology, Bonn, Germany; (b) Blinded, multirater comparison of EEGs of all PNES patients with no other clinically recognizable cause of EEG disturbance (n = 50) and healthy controls (n = 50).
Results: Of 187 consecutive patients with PNESs, 57 patients had PNESs and epilepsy (PNES+E), and 130 patients, PNESs alone. The diagnosis of additional epilepsy was based on ictal (video-) EEG or on the critical assessment of all clinical data by an experienced epileptologist. Retrospective review of all available EEG reports showed that 92.9% of patients in the PNES+E and 53.8% in the PNES-only group had one or more abnormal EEGs (median number of EEGs per patient, three; range, one to 42). In the PNES-only group, EEG changes were nonspecific in 42.3% of patients. Only 50 of 130 patients with PNESs alone had no other clinically recognizable cause of EEG disturbance and entered the controlled study. In this study, 18% of patients and 10% of controls had abnormal EEGs. The frequency of epileptiform EEG changes was similar to that in previous population studies in both groups (2.0%).
Conclusions: PNESs often occur in patients with organic brain disease. Even in patients with PNESs alone and no clinically recognizable cause of EEG disturbance, nonspecific abnormalities are found 1.8 times as often as in healthy controls. Interictal EEG changes are common in patients with PNESs and, in isolation, should not be interpreted as evidence of epilepsy.