Abstracts

Rationale: Nonepileptic seizures (NES) are a common problem encountered by epileptologists. Variability in semiology has been considered a feature of NES. We sought to study the stereotypy of NES and propose a semiological classification based on video EEG monitoring. Methods: Video EEG monitoring (VEM) records of patients who underwent evaluation from January 2002 to June 2007 at two tertiary care epilepsy centers were reviewed to identify those who had NES with or without a background of epilepsy. The diagnosis of NES had been made on the basis of the consensus opinion of two epilepsy specialists based on history, imaging, and VEM. The semiology of each event was visually analyzed in detail and entered into a statistical database. Type of movement, distribution, synchrony, symmetry, onset, offset, course, duration, vocalization, hyperventilation, eye movements and responsiveness of NES were evaluated to delineate a semiological classification. Nonepileptic seizures were classified into distinct groups according to the predominant motor manifestation. The stereotypic nature of different NES types and the degree of stereotypy within individual patients were studied. Results: A total of 330 NES from 61 patients were studied. There were 45 females and 16 males. Coexisting epilepsy was found in 13.1%. The mean number of seizures recorded per patient was 5 and the mean duration of VEM was 3 days. Based on semiology, six different NES types were delineated as follows; (1) Rhythmic motor NES characterized by rhythmic tremor or rigor like movements (46.7%). (2) Nonepileptic auras characterized by subjective sensations without any external manifestations, marked in the VEM records as ‘seizure button presses’ (23.6%). (3) Dialeptic NES characterized by unresponsiveness without motor manifestations (11.2%). (4) Complex motor NES characterized by complex movements such as flexion, extension, abduction, adduction, rotation, with or without clonic and myoclonic components of varying combinations and distribution (10%). (5) Hypermotor NES characterized by violent movements (3.3%). (6) Mixed NES where combinations of above seizure types were seen (5.2%). These NES types demonstrated stereotypic patterns in terms of the type of movements, distribution of movements, synchrony and symmetry of movements, eye closure at the onset, head movements, trunk movements, pelvic movements, responsiveness, hyperventilation, vocalization, onset, offset and course of the seizure. We have defined the characteristics of each NES type based on those features. The EEG was normal during dialeptic NES and nonepileptic auras. During other NES types, the EEG demonstrated characteristic patterns due to movement and electrode artifacts. In a given patient, all the seizures belonged to a single NES type in 82% of cases. Conclusions: The semiology of NES can be classified into six recognizable categories. Contrary to common belief, NES demonstrates stereotypy within and across patients.