Epilepsia, 45(11):1344–1350, 2004 Blackwell Publishing, Inc. C  2004 International League Against Epilepsy “Convulsive” Nonepileptic Seizures Have a Characteristic Pattern of Rhythmic Artifact Distinguishing Them from Convulsive Epileptic Seizures ∗ †‡Anita Vinton, ∗ John Carino, §Simon Vogrin, ‖Lachlan MacGregor, ∗ †Christine Kilpatrick, ∗ Zelko Matkovic, and ∗ †Terence J. O’Brien The Departments of ∗ Neurology and †Medicine, The Royal Melbourne Hospital, The University of Melbourne, Parkville; ‡Monash Institute of Neurological Diseases, Monash Medical Centre, Clayton; §Compumedics Limited Australia, Abbortsford, and // Clinical Epidemiology & Health Service Evaluation Unit, Royal Melbourne Hospital Parkville, Victoria, Australia Summary: Purpose: Approximately 30% of patients admit- ted for video-EEG monitoring have psychogenic nonepileptic seizures (PNES). Differentiation of “convulsive” PNES from convulsive seizures can be difficult. The EEG often displays rhythmic movement artifact that may resemble seizure activity and confound the interpretation. We sought to determine whether time–frequency mapping of the rhythmic EEG artifact during “convulsive” PNES reveals a pattern that differs from that of epileptic seizures. Methods: EEGs from 15 consecutive patients with “convul- sive” PNESs were studied with time–frequency mapping by us- ing NEUROSCAN and compared with 15 patients with con- vulsive epileptic seizures. Fast Fourier transforms (FFTs) were performed to determine the dominant frequency for 1- to 2-s windows every 2 s through the seizures. Results: The dominant frequency remained stable within a nar- row range for the duration of the PNES, whereas in the epileptic seizures, it evolved through a wide range. The coefficient of vari- ation of the frequency during the seizures was considerably less for patients without epilepsy (median, 15.0%; range, 7.2–23.7% vs. median, 58.0%; range, 34.8–92.1%; p < 0.001). The median frequency did not differ significantly between groups (4.2 vs. 4.6 Hz; p = 0.290). Conclusions: “Convulsive” PNES display a characteristic pat- tern on time–frequency mapping of the EEG artifact, with a stable, nonevolving frequency that is different from the evolv- ing pattern seen during an epileptic seizure. Key Words: Psy- chogenic nonepileptic seizures—Time–frequency mapping— EEG. Individuals with psychogenic nonepileptic seizures (PNES) have recurrent episodes of altered movement, sensation, or experience that resemble epileptic seizures but are not associated with abnormal electrical activ- ity in the brain (1). The etiology of PNES remains un- clear; however, they are presumed to relate to underlying psychogenic disturbances, with multiple factors includ- ing personality traits playing a role in both etiology and prognosis (2). PNES represent a common diagnostic and management problem, not just for the neurologist, but also for general practitioners, emergency departments, and other treating physicians. The estimated prevalence of PNES is between 2 to 33 per 100,000 individuals, making PNES one of the more common conversion disorders in the community (3). Accepted April 25, 2004. Address correspondence and reprint requests to Dr. T. O’Brien at The Department of Medicine, RMH, The University of Melbourne, Royal Parade, Parkville, 3050, Victoria, Australia. E-mail: obrientj@ unimelb.edu.au It has been reported that between 11 and 54% of patients admitted for inpatient video-EEG monitoring (VEM) are diagnosed as having PNES (1,4–7). A significant propor- tion of patients requiring intubation for status epilepticus are ultimately diagnosed with PNESs, resulting in poten- tially serious morbidity to the patient, and considerable cost to the community (8). The differentiation between epileptic and nonepileptic seizures can be difficult. Seizure semiology is important in the diagnostic algorithm, and a plethora of features have been reported as being more likely associated with PNES. These have included a stable ictal heart rate (9), induction of the event with suggestion (10), eyes closed versus open, pelvic thrusting or “no-no” head shaking during the event (11), and even the presence of a teddy bear brought in dur- ing EEG monitoring (12). However, none of these features alone is diagnostic of PNES, as all can be seen on occa- sions during epileptic seizures. VEM is the investigation of choice in confirming the diagnosis of seizure disor- ders. However, even with EEG monitoring, the diagnosis 1344