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Psychogenic non-epileptic seizures (PNES) are the most common manifestation of functional (psychogenic) neurological symptoms. Clinically, they consist of intermittent episodes that resemble epileptic seizures and can involve changes in behaviour, movement, sensation, autonomic function or consciousness. To date, there are no positive EEG features that have been identified that are diagnostic of PNES and therefore, the diagnosis is primarily based on clinical assessment and the absence of epileptic activity during the seizure.
Our goal was to identify a positive marker of PNES, by assessing EEG spectral power changes prior to non-epileptic attacks.
We hypothesised that decreases in β power (desynchronisation in the 13–30 Hz band) might occur prior to a non-epileptic seizure. β-Desynchronisation is known to occur prior to cued movement (event-related desynchronisation, ERD) or self-paced movement and was recently shown to occur prior to functional myoclonic jerks.1
We recruited three patients previously diagnosed with PNES from the Movement Disorder outpatient clinics at the National Hospital for Neurology and Neurosurgery. Three EEG recordings of patients with convulsive epileptic attacks were used as control. The study was approved by the local Ethics Committee and informed consent was obtained.
Patients were seated in a comfortable chair while a 32-channel EEG was recorded and a video was made. We asked each participant to sit in a relaxed position with their eyes open and to let attacks happen in their usual way …