title: Patterns of habituation and clinical fluctuations in migraine.
abstract: BACKGROUND
  Habituation deficit, suggesting a deregulation of cortical excitability, represents a typical hallmark of interictal stages of migraine. We previously demonstrated that several neurophysiological markers of altered cortical excitability are significantly correlated to spontaneous clinical fluctuations of migraine. We therefore aimed at verifying whether clinical fluctuations are correlated to specific patterns of somatosensory evoked potential (SEP) habituation.
  
  
  METHODS
  We analyzed habituation after median nerve stimulation of both high-frequency oscillations (HFOs) and N20 SEP in 25 migraine patients and 18 healthy volunteers. Subjects underwent six consecutive series of 500 stimuli.
  
  
  RESULTS
  Migraine patients as a whole showed a significant habituation deficit of the N20 response. Moreover, spontaneously worsening patients show a clear potentiation of this wave in the last block of stimuli, whereas in spontaneously improving patients the N20 amplitude remained stable. Presynaptic HFOs were smaller in worsening patients and larger in improving ones, but they did not undergo habituation in patients as well as in healthy subjects.
  
  
  CONCLUSIONS
  Potentiation of the N20 response in spontaneously worsening migraineurs confirms that the reduction of the thalamocortical drive plays a major role in migraine pathogenesis. Moreover, the stable pattern we observed in spontaneously improving patients suggests that compensatory mechanisms can also play an important role. The normal response to repeated stimuli of HFOs in migraineurs might indicate that, although its initial amount depends on clinical conditions, high-frequency thalamocortical drive remains stable during the stimulation and probably reflects the activity of a buffer mechanism.
authors.affiliation: Department of Neurosciences, Catholic University, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Restuccia
authors.forename: Catello
authors.initials: C
authors.lastname: Vollono
authors.forename: Daniela
authors.initials: D
authors.lastname: Virdis
authors.forename: Ivana
authors.initials: I
authors.lastname: del Piero
authors.forename: Lucia
authors.initials: L
authors.lastname: Martucci
authors.forename: Sergio
authors.initials: S
authors.lastname: Zanini
mesh_terms: D000328:Adult; D005260:Female; D006185:Habituation, Psychophysiologic; D006801:Humans; D017774:Long-Term Potentiation; D008297:Male; D008881:Migraine Disorders / Q000503:physiopathology*; D009415:Nerve Net / Q000503:physiopathology*; D013003:Somatosensory Cortex / Q000503:physiopathology*; D013788:Thalamus / Q000503:physiopathology*; D055815:Young Adult
keywords: Migraine pathogenesis; excitability; high-frequency oscillations; somatosensory evoked potentials; thalamus