One step forward, several more to go: classification of ...

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matches particular subjective PNES experiences. Some information suggests that the likelihood of antecedent sexual abuse can be predicted by the way patients experience their seizures and by their clinical presentation.6 More dramatic seizure presentations have also been linked to higher rates of psychopathology and poorer outcome.7 9 12 It is possible that the use of more objectively derived PNES subtypes could allow inferences about the background of the patients or other factors that might be useful therapeutically.

One step forward, several more to go: classification of psychogenic non-epileptic seizures based on automatic clustering Markus Reuber,1 Rod Duncan2

Competing interests None. Provenance and peer review Commissioned; not externally peer reviewed.

In ordinary neurological practice, the diagnosis of psychogenic non-epileptic seizures (PNES) is often made by exclusion, or on the grounds that seizures lack features of epilepsy. With the exception of linguistic and interactional markers in the conversation with the patient about their symptoms,1 few ‘positive’ signs of PNES have been described. Therefore, this effort to improve our knowledge of the clinical semiology of PNES is welcome. Hubsch et al2 used multiple correspondence analysis and cluster analysis of video-EEG recordings of PNES to identify five clinical subtypes of attack. The authors conclude that their classification of PNES may provide useful criteria for clinical diagnosis, presumably by giving clinicians a series of ‘models’ they can hold in their heads for evaluation of clinical descriptions of attacks. This study makes a significant contribution to the evidence that the label PNES does not describe a single or uniform disorder.3 Previous studies have shown that there are major differences between subgroups of patients with PNES in terms of demographic features (such as the lack of a preponderance of women in older people or in patients with learning disabilities (LD)),4 5 aetiology (eg, lower rates of a history of sexual abuse in older patients or those with LD, and higher rates of physical health worries in older people),4 5 clinical features (eg, more seizures from sleep and more seizures leading to hospital admissions in patients who have experienced sexual abuse)6 and outcome (better in patients with less 1

University of Sheffield, Royal Hallamshire Hospital, Sheffield, UK; 2West of Scotland Regional Epilepsy Service, Southern General Hospital, Glasgow, UK Correspondence to Dr Markus Reuber, University of Sheffield, Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF, UK; [email protected] 946

emotional dysregulation, fewer somatic symptoms and higher educational achievements).7 Hubsch et al2 suggest that there is also objective evidence of heterogeneity in terms of visible PNES manifestations. There are now many studies of the video-EEG observed manifestations of PNES in the literature, some that have evaluated individual features for their discriminatory value with respect to epilepsy8 and some that have described PNES subtypes.9 One potential drawback of studies based on the analysis of visible seizure manifestations is that they do not take account of subjective seizure experiences. Given that the current diagnostic manuals interpret PNES as a ‘mental disorder,’ it is surprising how little research has explored the subjective aspects of PNES semiology. Another drawback of studies based on video-EEG analysis is that they typically capture a small number of seizures over a relatively short period. It may therefore be that these studies underestimate the variability of PNES semiology over time.10 It is also likely that PNES manifestations are often not described in the clinic in the same way as they appear on video.11 Thus, the process of extrapolating back from video studies to habitual seizure manifestations as described in the clinic is not entirely straightforward. Looking towards the future, it would be of interest to explore whether PNES subtypes can tell us anything else about the patient, especially in terms of optimal treatment or likely prognosis. It would also be interesting to see to what extent the seizure clustering detected by the method used by Hubsch et al2 (see page 955) can be predicted by information obtained from patients and seizure witnesses, and whether the proposed subclassification based on visible seizure manifestations

Received 4 April 2011 Accepted 25 April 2011 Published Online First 25 May 2011 J Neurol Neurosurg Psychiatry 2011;82:946. doi:10.1136/jnnp.2011.246751

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Reuber M, Monzoni C, Sharrack B, et al. Using conversation analysis to distinguish between epilepsy and non-epileptic seizures: a prospective blinded multirater study. Epilepsy Behav 2009;16:139e44. Hubsch C, Baumann C, Hingray C, et al. Clinical classification of psychogenic non-epileptic seizures based on video-EEG analysis and automatic clustering. J Neurol Neurosurg Psychiatry 2011;82:955e60. Reuber M. The etiology of psychogenic non-epileptic seizures: toward a biopsychosocial model. Neurol Clin 2009;27:909e24. Duncan R, Oto M. Psychogenic non-epileptic seizures in patients with learning difficulties: comparison with patients with no learning difficulties. Epilepsy Behav 2008;12:183e6. Duncan R, Oto M, Martin E, et al. Late onset psychogenic nonepileptic attacks. Neurology 2006;66:1644e7. Selkirk M, Duncan R, Oto M, et al. Clinical differences between patients with nonepileptic seizures who report antecedent sexual abuse and those who do not. Epilepsia 2008;49:1446e50. Reuber M, Pukrop R, Bauer J, et al. Outcome in psychogenic nonepileptic seizures: 1 to 10 year follow-up in 164 patients. Ann Neurol 2003;53:305e11. Avbersek A, Sisodiya S. Does the primary literature provide support for clinical signs used to distinguish psychogenic nonepileptic seizures from epileptic seizures? J Neurol Neurosurg Psychiatry 2010;81:719e25. Groppel G, Kapitany T, Baumgartner C. Cluster analysis of clinical seizure semiology of psychogenic nonepileptic seizures. Epilepsia 2000;41:610e14. Seneviratne U, Reutens D, D’Souza W. Stereotypy of psychogenic nonepileptic seizures: insights from video-EEG monitoring. Epilepsia 2010;51:1159e68. Syed TU, Lafrance WC Jr, Kahriman ES, et al. Can semiology predict psychogenic nonepileptic seizures? A prospective study. Ann Neurol. Published Online First: 6 December 2010. doi:10.1002/ana.22345. Reuber M, House AO, Pukrop R, et al. Somatization, dissociation and psychopathology in patients with psychogenic nonepileptic seizures. Epilepsy Res 2003;57:159e67.

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One step forward, several more to go: classification of psychogenic non-epileptic seizures based on automatic clustering Markus Reuber and Rod Duncan J Neurol Neurosurg Psychiatry 2011 82: 946 originally published online May 25, 2011

doi: 10.1136/jnnp.2011.246751

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