title: Circadian Change in Blink Reflex Recovery in Restless Legs Syndrome.
abstract: BACKGROUND
  Restless legs syndrome (RLS) is associated with dysfunction of the dopaminergic systems in the pathways that specifically link the sensory input and motor output. Keeping in mind that clinical symptomatology in RLS and cerebrospinal fluid dopamine concentrations in healthy individuals show changes throughout the day, we hypothesized that excitability of the related pathways increases during the night in RLS, and in the present study, we aimed to analyze our hypothesis by the assessment of blink reflex (BR) recovery.
  
  
  METHODS
  Eleven patients with primary RLS and eight age- and gender-matched healthy subjects were included in the study. All participants underwent detailed interviews and neurological examinations. BR responses were recorded after single and paired supraorbital stimulation during the early afternoon and late at night. For double stimulation, interstimulus intervals (ISI) of 100, 300, and 500 ms were used. Daytime and nighttime investigations were separately compared between the patient and control groups (between-group analyses). In-group analyses were conducted between daytime and nighttime investigations of the patient and control groups.
  
  
  RESULTS
  BR responses to single stimuli were normal in all participants at all sessions. R2 recovery was the highest in the patient group during nighttime investigations. In-group analysis showed a reduction of R2 recovery during the night in healthy subjects. R2 recoveries at ISIs of 300 and 500 ms at nighttime were higher in RLS patients but did not reach statistical significance.
  
  
  CONCLUSIONS
  The BR circuit is less excitable during the night in healthy individuals, whereas the reduction of excitability is lost in RLS. Despite the limited number of included subjects, we suggest that the normal circadian modulation of the BR circuit is lost in RLS.
authors.affiliation: Department of Neurology, İstanbul University Cerrahpaşa School of Medicine, İstanbul Turkey.
authors.forename: Nurten
authors.initials: N
authors.lastname: Uzun
authors.affiliation: Department of Neurology, İstanbul University Cerrahpaşa School of Medicine, İstanbul Turkey.
authors.forename: Ayşegül
authors.initials: A
authors.lastname: Gündüz
authors.affiliation: Department of Neurology, İstanbul University Cerrahpaşa School of Medicine, İstanbul Turkey.
authors.forename: Derya
authors.initials: D
authors.lastname: Karadeniz
authors.affiliation: Department of Neurology, İstanbul University Cerrahpaşa School of Medicine, İstanbul Turkey.
authors.forename: Meral E
authors.initials: ME
authors.lastname: Kiziltan
keywords: Blink reflex; blink reflex recovery; brainstem excitability; circadian rhythm; restless legs syndrome