title: Is lack of habituation of evoked potential a biological marker of migraine?
abstract: OBJECTIVE
  The aim of this study was to evaluate sensitization and habituation of median somatosensory-evoked potential (MSEP) and correlate with migraine characteristics and allodynia.
  
  
  METHODS
  A total of 100 migraineurs were included; their demographic features, migraine characteristics, and the presence of allodynia were noted. The patients were grouped into episodic migraine (EM), chronic migraine (CM), and medication overuse headache (MOH). Three consecutive MSEPs averaging 100 epochs each were recorded. The N19 amplitude of block 1 was considered for sensitization, and amplitudes of block 2 and 3 compared with block 1 were considered for habituation and augmentation. MSEP was also evaluated in 29 controls.
  
  
  RESULTS
  Seventy-one percent of migraineurs had a lack of habituation as opposed to 27.6% of controls (P<0.001). The lack of habituation was observed in all subtypes of migraine, and patients with EM (76.1%) had greater lack of habituation compared with patients with MOH (61.3%; P=0.03). Augmentation was present in 61% migraineurs and was more frequent in CM (73.9%) compared with EM (63%) and MOH (48%). Sensitization was not significantly different in migraineurs compared with controls (8.23±4.07 vs.7.99±2.84 μV; P=0.72), but patients with allodynia had greater sensitization compared with those without allodynia (8.57±4.32 vs. 6.89±2.55 μV; P=0.03). The sensitization was also related to age and duration of migraine.
  
  
  CONCLUSIONS
  The migraineurs have impaired cortical inhibition to somatosensory stimuli, and sensitization may be a feature of chronicity.
authors.affiliation: Department of Neurology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India.
authors.forename: Jayantee
authors.initials: J
authors.lastname: Kalita
authors.forename: Sanjeev K
authors.initials: SK
authors.lastname: Bhoi
authors.forename: Usha K
authors.initials: UK
authors.lastname: Misra
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D006801:Humans; D006930:Hyperalgesia / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008881:Migraine Disorders / Q000175:diagnosis* / Q000503:physiopathology*; D010147:Pain Measurement; D010812:Physical Stimulation; D055815:Young Adult