title: Pearls and pitfalls: electrophysiology for primary headaches.
abstract: BACKGROUND
  Primary headaches are functional neurological diseases characterized by a dynamic cyclic pattern over time (ictal/pre-/interictal). Electrophysiological recordings can non-invasively assess the activity of an underlying nervous structure or measure its response to various stimuli, and are therefore particularly appropriate for the study of primary headaches. Their interest, however, is chiefly pathophysiological, as interindividual, and to some extent intraindividual, variations preclude their use as diagnostic tools.
  
  
  OBJECTIVE
  This article will review the most important findings of electrophysiological studies in primary headache pathophysiology, especially migraine on which numerous studies have been published.
  
  
  RESULTS
  In migraine, the most reproducible hallmark is the interictal lack of neuronal habituation to the repetition of various types of sensory stimulations. The mechanism subtending this phenomenon remains uncertain, but it could be the consequence of a thalamocortical dysrythmia that results in a reduced cortical preactivation level. In tension-type headache as well as in cluster headache, there seems to be an impairment of central pain-controlling mechanisms but the studies are scarce and their outcomes are contradictory. The discrepancies between studies might be as a result of methodological differences as well as patients' dissimilarities, which are also discussed.
  
  
  CONCLUSIONS
  Electrophysiology is complementary to functional neuroimaging and will undoubtedly remain an important tool in headache research. One of its upcoming applications is to help select neurostimulation techniques and protocols that correct best the functional abnormalities detectable in certain headache disorders.
authors.affiliation: Headache Research Unit, University Department of Neurology, CHR Citadelle, Liege 4000, Belgium. dmagis@chu.ulg.ac.be
authors.forename: Delphine
authors.initials: D
authors.lastname: Magis
authors.forename: Alessandro
authors.initials: A
authors.lastname: Vigano
authors.forename: Simona
authors.initials: S
authors.lastname: Sava
authors.forename: Tullia Sasso
authors.initials: TS
authors.lastname: d'Elia
authors.forename: Jean
authors.initials: J
authors.lastname: Schoenen
authors.forename: Gianluca
authors.initials: G
authors.lastname: Coppola
mesh_terms: D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping / Q000379:methods*; D003951:Diagnostic Errors / Q000517:prevention & control*; D004569:Electroencephalography / Q000379:methods*; D051270:Headache Disorders, Primary / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D008959:Models, Neurological
keywords: Headache; blink reflex; electrophysiology; evoked potentials; migraine; neurostimulation; nociception