title: Hyperventilation induces sympathetic overactivation in mesial temporal epilepsy.
abstract: OBJECTIVE
  Hyperventilation (HV) during electroencephalography (EEG) is a standard clinical procedure to trigger seizures in patients affected by mesial temporal lobe epilepsy (MTLE). Despite the pathophysiology of this susceptibility to HV is not definitively understood, it may be hypothesized to be related to ictal and interictal sympathetic nervous system abnormalities, the presence of which is well known in MTLE patients. In order to test this hypothesis we investigated the HV effect on heart rate variability (HRV) in a group of MTLE patients, compared to a matched group of healthy controls.
  
  
  METHODS
  Forty patients affected by MTLE and 40 age- and sex-matched controls were enrolled in the study. In those subjects, a standard electroencephalographic recording has been acquired and the high and the low frequency components (HF, LF) of heart rate variability (HRV) and their ratio (LF/HF) have been analyzed at rest and during the HV. Indeed, LF/HF is a reliable index of sympathetic tone modulation.
  
  
  RESULTS
  HRV did not differ between MTLE and healthy subjects at rest, whereas HV induced a significant LF/HF increase only in MTLE. Within the MTLE group, males showed higher LF/HF increase during HV respect to females, while no differences related to the side of the epileptic focus were found.
  
  
  CONCLUSIONS
  MTLE patients showed an increased sympathetic response to HV compared to healthy subjects. HRV analysis points towards an autonomic overactivation as a pathophysiological pathway subtending seizure triggered by hyperventilation in MTLE. Autonomic susceptibility in MTLE may help to explain the increased prevalence of arrhythmic events in these patients, potentially predisposing to Sudden Unexpected Death in Epilepsy (SUDEP).
authors.affiliation: Clinical Neurology, Campus Biomedico, University of Rome, Rome, Italy. Electronic address: gianni.assenza@gmail.com.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Assenza
authors.affiliation: Department of Neurology and Psychiatry, Sapienza University, Policlinico Umberto 1 Hospital, Rome, Italy.
authors.forename: Oriano
authors.initials: O
authors.lastname: Mecarelli
authors.affiliation: Clinical Neurology, Campus Biomedico, University of Rome, Rome, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Tombini
authors.affiliation: Department of Neurology and Psychiatry, Sapienza University, Policlinico Umberto 1 Hospital, Rome, Italy.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Pulitano
authors.affiliation: Clinical Neurology, Campus Biomedico, University of Rome, Rome, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Pellegrino
authors.affiliation: Clinical Neurology, Campus Biomedico, University of Rome, Rome, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Benvenga
authors.affiliation: Clinical Neurology, Campus Biomedico, University of Rome, Rome, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Assenza
authors.affiliation: Clinical Neurology, Campus Biomedico, University of Rome, Rome, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Campana
authors.affiliation: Clinical Neurology, Campus Biomedico, University of Rome, Rome, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Di Pino
authors.affiliation: Clinical Neurology, Campus Biomedico, University of Rome, Rome, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Di Lazzaro
mesh_terms: D001921:Brain / Q000503:physiopathology; D004562:Electrocardiography; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies
keywords: Heart rate variability; Hyperventilation; Mesial temporal lobe epilepsy; Sympathetic nervous system