title: Lateralized nociceptive blink reflex habituation deficit in episodic cluster headache: Correlations with clinical features.
abstract: BACKGROUND
  We previously observed impaired habituation mechanisms of the conventional blink reflex (BR) in patients with episodic cluster headache (ECH) during the bout, studying only the affected side. Here, we have studied the nociceptive-specific BR (nBR) both on the affected and non-affected sides, and in relation to clinical features.
  
  
  METHODS
  We recorded nBR in 18 ECH patients during the bout, and in 18 healthy volunteers (HVs). We compared pain threshold, area, and habituation of the nBR, recorded both for the affected and non-affected sides.
  
  
  RESULTS
  In patients, the pain threshold on the affected side was lower than that of the non-affected side (p = 0.009), and lower than in HVs (p = 0.038). Reflex area was decreased on both sides (p < 0.05) compared with HVs, whereas habituation was significantly impaired only on the affected side (p = 0.025 vs. HVs; p = 0.003 vs. non-affected). The habituation slope was positively correlated with the number of days since the onset of the bout and the daily attack frequency.
  
  
  CONCLUSIONS
  Our data reflect lateralized pathological variations in craniofacial nociception in ECH patients over the course of the cluster period. We hypothesized that this is due to malfunctioning of mechanisms that regulate hypothalamic activity and descending aminergic controls.
authors.affiliation: Department of Neurophysiology of Vision and Neurophthalmology, G.B. Bietti Foundation-IRCCS, Italy gianluca.coppola@gmail.com.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Coppola
authors.affiliation: Don Carlo Gnocchi Onlus Foundation, Italy.
authors.forename: Cherubino
authors.initials: C
authors.lastname: Di Lorenzo
authors.affiliation: Department of Medico-Surgical Sciences and Biotechnologies, "Sapienza" University of Rome Polo Pontino, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Bracaglia
authors.affiliation: Department of Medico-Surgical Sciences and Biotechnologies, "Sapienza" University of Rome Polo Pontino, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Di Lenola
authors.affiliation: Department of Neurophysiology of Vision and Neurophthalmology, G.B. Bietti Foundation-IRCCS, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Parisi
authors.affiliation: IRCCS-Neuromed, Pozzilli (IS), Italy.
authors.forename: Armando
authors.initials: A
authors.lastname: Perrotta
authors.affiliation: Department of Medico-Surgical Sciences and Biotechnologies, "Sapienza" University of Rome Polo Pontino, Italy.
authors.forename: Mariano
authors.initials: M
authors.lastname: Serrao
authors.affiliation: IRCCS-Neuromed, Pozzilli (IS), Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Pierelli
mesh_terms: D000328:Adult; D001767:Blinking / Q000502:physiology*; D003027:Cluster Headache / Q000175:diagnosis* / Q000503:physiopathology; D004558:Electric Stimulation / Q000009:adverse effects; D005260:Female; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement / Q000379:methods*; D017288:Pain Threshold / Q000502:physiology*
keywords: Cluster headache; blink reflex; habituation; lateralization; pain