Lack of habituation of nociceptive evoked responses and pain sensitivity during migraine attack.
OBJECTIVE
The aim of the present study was to investigate the habituation of subjective pain sensation to CO(2) laser stimulus, in relation to the amplitude modifications of the cortical evoked responses (LEPs), during both the migraine attack and the not symptomatic phase.


METHODS
Fourteen migraine patients were selected and compared with 10 healthy controls. Eight patients were evaluated during both the pain-free and the attack phases. Three following series of 20 averaged LEPs were recorded, stimulating the hands and the supraorbital zones: during the attack, two consecutive series of 20 averaged LEPs were carried out. The subjective sensation was requested for each laser stimulus, using a 0-10 points Verbal Rating Scale (VRS).


RESULTS
In normal subjects the N2-P2 waves amplitude showed habituation across the three repetitions, which correlated with the habituation of the subjective rating of the stimulus. During the not symptomatic phase, patients showed a lack of habituation of the N2-P2 amplitude when the hand and the face was stimulated, with a pattern of increase of the pain rating across the three repetitions; in addition there was a lack of correlation between the LEPs amplitude and the subjective sensation. During the attack, the LEPs amplitude and the pain rating were increased when the face was stimulated, but they did not habituate across the two repetitions, likely the pain-free condition. The percent LEPs amplitude variation across the three repetitions correlated with the main indices of migraine severity, mainly when the supraorbital zone was stimulated.


CONCLUSIONS
The abnormal cortical excitability in migraine could condition an anomalous behavior of nociceptive cortex during the interictal phase of migraine: it persists during the acute phase, and correlates with the frequency and duration of migraine.


CONCLUSIONS
The reduced habituation of the nociceptive cortex may concur with the onset and evolution of headache.
Neurologic and Psychiatric Sciences Department, Bari University, Clinica Neurologica, Policlinico, Piazza Giulio Cesare 11, 70124 Bari. m.detommaso@neurol.uniba
Marina
M
de Tommaso
Luciana
L
Lo Sito
Olimpia
O
Di Fruscolo
Michele
M
Sardaro
Maria
M
Pia Prudenzano
Paolo
P
Lamberti
Paolo
P
Livrea
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D002540:Cerebral Cortex / Q000503:physiopathology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D006225:Hand / Q000294:innervation / Q000528:radiation effects; D006801:Humans; D007834:Lasers; D016014:Linear Models; D008881:Migraine Disorders / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods