Use of noninvasive induction techniques in the diagnosis of PNES.

The diagnosis of psychogenic nonepileptic seizures (PNES) remains challenging. In the correct clinical setting with prolonged electroencephalography (EEG) monitoring, the specificity of provocative techniques to distinguish induced epileptic event from a nonepileptic event approaches 90%. We report our epilepsy monitoring unit (EMU) experience with the use of noninvasive verbal suggestion (VS) during hyperventilation (HV), photic stimulation (PS) as induction technique in making the diagnosis of PNES. In total, 189/423 patients were diagnosed with PNES during the EMU evaluation. Of the 189, 20 had mixed disorder and 169 patients had only PNES, 80 patients (47.3%) had a PNES with induction, and the remaining 89 of 169 patients (52.7%) had a spontaneous PNES episode that did not require induction. Verbal suggestion during HV and PS confirmed the diagnosis of PNES in 47% of the patients who otherwise did not have spontaneous events. Within the group who was diagnosed with PNES following induction, antiepileptic drugs (AEDs) were stopped in 53% of the patients. We believe that this is a large proportion of patients that would possibly remain undiagnosed if no induction were performed.