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Neuropsychiatry
Original research
Changes in the heartbeat-evoked potential are associated with functional seizures
  1. Samia Elkommos1,2,
  2. David Martin-Lopez3,
  3. Akihiro Koreki4,5,
  4. Claire Jolliffe3,
  5. Rohan Kandasamy6,7,
  6. Marco Mula2,8,
  7. Hugo D Critchley9,10,
  8. Mark J Edwards11,12,
  9. Sarah Garfinkel13,
  10. Mark P Richardson1,14,
  11. Mahinda Yogarajah7,15
  1. 1 School of Neuroscience, King's College London Institute of Psychiatry Psychology and Neuroscience, London, UK
  2. 2 Epilepsy Group, St George's Hospital Atkinson Morley Regional Neuroscience Centre, London, UK
  3. 3 Clinical Neurophysiology, St George's Hospital Atkinson Morley Regional Neuroscience Centre, London, UK
  4. 4 Psychiatry, National Hospital Organisation Shimofusa Psychiatric Medical Center, Chiba, Japan
  5. 5 Neuroscience Research Centre, St George's University of London, London, UK
  6. 6 Clinical Neurophysiology, National Hospital for Neurology and Neurosurgery, London, UK
  7. 7 Department of Clinical and Experimental Epilepsy, University College London, London, UK
  8. 8 Institute of Medical and Biomedical Education, St George's University of London, London, UK
  9. 9 Neuroscience, Brighton and Sussex Medical School, Brighton, UK
  10. 10 Research and Development, Sussex Partnership NHS Foundation Trust, Worthing, UK
  11. 11 Centre for Clinical Neuroscience, St George's University of London, London, UK
  12. 12 Atkinson Morley Regional Neuroscience Centre, St George's Hospital, London, UK
  13. 13 Institute of Cognitive Neuroscience, University College London Institute of Cognitive Neuroscience, London, UK
  14. 14 Centre for Epilepsy, King's College Hospital NHS Foundation Trust, London, UK
  15. 15 Neurology, National Hospital for Neurology and Neurosurgery, London, UK
  1. Correspondence to Dr Mahinda Yogarajah, Clinical and Experimental Epilepsy, University College London Department of Clinical and Experimental Epilepsy, London, London, UK; m.yogarajah{at}ucl.ac.uk

Abstract

Background Patients with functional seizures (FS) can experience dissociation (depersonalisation) before their seizures. Depersonalisation reflects disembodiment, which may be related to changes in interoceptive processing. The heartbeat-evoked potential (HEP) is an electroencephalogram (EEG) marker of interoceptive processing.

Aim To assess whether alterations in interoceptive processing indexed by HEP occur prior to FS and compare this with epileptic seizures (ES).

Methods HEP amplitudes were calculated from EEG during video-EEG monitoring in 25 patients with FS and 19 patients with ES, and were compared between interictal and preictal states. HEP amplitude difference was calculated as preictal HEP amplitude minus interictal HEP amplitude. A receiver operating characteristic (ROC) curve analysis was used to evaluate the diagnostic performance of HEP amplitude difference in discriminating FS from ES.

Results The FS group demonstrated a significant reduction in HEP amplitude between interictal and preictal states at F8 (effect size rB=0.612, false discovery rate (FDR)-corrected q=0.030) and C4 (rB=0.600, FDR-corrected q=0.035). No differences in HEP amplitude were found between states in the ES group. Between diagnostic groups, HEP amplitude difference differed between the FS and ES groups at F8 (rB=0.423, FDR-corrected q=0.085) and C4 (rB=0.457, FDR-corrected q=0.085). Using HEP amplitude difference at frontal and central electrodes plus sex, we found that the ROC curve demonstrated an area under the curve of 0.893, with sensitivity=0.840 and specificity=0.842.

Conclusion Our data support the notion that aberrant interoception occurs prior to FS. Changes in HEP amplitude may reflect a neurophysiological biomarker of FS and may have diagnostic utility in differentiating FS and ES.

  • EPILEPSY
  • FUNCTIONAL NEUROLOGICAL DISORDER
  • NEUROPSYCHIATRY
  • NEUROPHYSIOLOGY
  • EEG

Data availability statement

Data are available upon reasonable request. Derived data supporting the findings of this study are available from the corresponding author on request.

https://doi.org/10.1136/jnnp-2022-330167

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    Data availability statement

    Data are available upon reasonable request. Derived data supporting the findings of this study are available from the corresponding author on request.

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    Footnotes

    • Contributors Study conception and study design: SE, DM-L, AK and MY; data collection: SE, AK,and CJ; data analysis: SE, DM-L and MY; interpretation of results: SE, DM-L, AK, RK, MM, HDC, MJE, SG, MPR and MY; preparation of the draft of the manuscript: SE, DM-L and MY. All authors contributed to the critical revision of the manuscript, reviewed the results and approved the final version of the manuscript. MY is the guarantor for this study.

    • Competing interests MM is editor-in-chief of Epilepsy & Behavior. MJE received honoraria for educational activities from Merz Pharma, UCB and the International Parkinson’s Disease and Movement Disorders Society; received royalties from the Oxford University Press; and provided expert testimony in clinical negligence and personal injury matters. MY carries out independent expert medicolegal work including in relation to functional neurological disorders.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.