title: Effects of vagus nerve stimulation on pupillary function.
abstract: BACKGROUND
  Chronic vagus nerve stimulation (VNS) is a recognized treatment for refractory epilepsy and depression. The vagus nerve projects to several brainstem autonomic structures. As pupillary measures are an easy and non-invasive method to evaluate autonomic functioning, we used resting diameter and light reflex measures to investigate the influence of VNS on the human central autonomic nervous system.
  
  
  METHODS
  We studied 21 patients (7 with major depression, 14 with epilepsy) treated with chronic VNS (30s ON, 5 min OFF stimulation trains). Resting pupil size and light reflex measures were compared in consecutive intervals with (ON) and without stimulation (OFF).
  
  
  RESULTS
  Compared to the OFF condition, the ON condition was associated with a significant increase in resting pupil diameter, but did not affect light reflex measures. There was no group difference between the two populations of patients (depression and epilepsy) on any of the pupil measures.
  
  
  CONCLUSIONS
  VNS at clinically significant levels increases resting pupil diameter.
authors.affiliation: Department of Psychology, UQAM, Canada; Department of Psychiatry, CHUM, Canada.
authors.forename: Véronique
authors.initials: V
authors.lastname: Desbeaumes Jodoin
authors.affiliation: Department of Psychiatry, CHUM, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Lespérance
authors.affiliation: Division of Neurology, CHUM, Canada.
authors.forename: Dang K
authors.initials: DK
authors.lastname: Nguyen
authors.affiliation: Division of Neurosurgery, CHUM, Canada.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Fournier-Gosselin
authors.affiliation: Department of Psychology, UQAM, Canada; Department of Psychiatry, CHUM, Canada. Electronic address: Francois.Richer@uqam.ca.
authors.forename: Francois
authors.initials: F
authors.lastname: Richer
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001767:Blinking / Q000502:physiology; D003865:Major Depressive Disorder / Q000628:therapy; D004827:Epilepsy / Q000628:therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011680:Pupil / Q000502:physiology*; D011930:Reaction Time; D055536:Vagus Nerve Stimulation / Q000379:methods*; D055815:Young Adult
keywords: Autonomic nervous system; Locus coeruleus; Neuromodulation; Pupillary light reflex; Pupillography