Attenuated heart-brain integration predicts functional non-epileptic seizures

Background Patients with functional seizures (FS) can experience dissociation (depersonalisation) before their seizures. Depersonalisation encompasses a feeling of disembodiment, putatively caused by reduced afferent visceral mapping, that is, changes in interoceptive processing. The heartbeat-evoked potential (HEP) is an electroencephalographic (EEG) index of synchronised neural responses to individual heart- beats, and a marker of interoceptive representation. HEP amplitude is reported to be reduced in dep- ersonalisation-derealisation disorder. Purpose To assess whether alterations in interoceptive processing indexed by the HEP occur prior to FSs, 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 compared between interictal and preictal states. Results The FS group demonstrated a significant reduction in HEP amplitude between interictal and preictal states at F8 (rB=0.612, p=0.006) and C4 (rB=0.600, p=0.007). No differences in HEP amplitude were found between interictal and preictal states in the ES group. Findings were not related to heart rate, mean ECG or QRS amplitudes, which did not differ between states or groups. Conclusion Our data support the notion that aberrant interoception underpins disembodiment prior to dissociative FS. Changes in HEP amplitude may reflect a neurophysiological biomarker of FS.