Habituation of single CO2 laser–evoked responses during interictal phase of migraine

Abstract

A reduced habituation of averaged laser–evoked potential (LEP) amplitudes was previously found in migraine patients. The aim of the present study was to assess the habituation of single LEP responses and pain sensation during the interictal phase in migraine patients. Fourteen migraine patients were compared with ten control subjects. The pain stimulus was laser pulses, generated by CO 2 laser, delivered to right supraorbital zone. Patients were evaluated during attack–free conditions. The LEP habituation was studied by measuring the changes of LEP amplitudes across and within three consecutive repetitions of 21 non–averaged trials. In migraine patients the N2–P2 wave amplitudes did not show a tendency toward habituation across and, above all, within the three repetitions. Anomalous behaviour of nociceptive cortex during the interictal phase of migraine may predispose patients to headache occurrence and persistence.

Altered processing of sensory stimuli in patients with migraine

“…128 This difference with the data on LEPs can be explained by the different methodologies used, which involved stimulation of different nociceptive afferents. 129 Similarly to the cortical evoked potentials elicited by non noxious stimuli, LEPs 75,130 and CHEPs 131 show habituation deficits in patients with migraine between attacks. However, in contrast with non noxious cortical evoked potentials, the lack of habituation of LEPs persists during the attack, and is associated with an increased N2-P2 amplitude.…”

“…nBR habituation normal izes during migraine attacks, 74 and individuals at risk of developing migraine lack nBR habituation deficits, 86 whereas habituation of nociceptive laser evoked poten tials (LEPs, discussed further below) remains deficient. 75 Patients with migraine also show temporal summation of the nBR. 122 Brief radiant heat pulses generated by CO 2 laser stim ulation or contact thermode delivered stimuli excite Aδ and C fibre thermonociceptors in superficial skin layers.…”

Deficient Pain Modulatory Systems in Patients with Mild Traumatic Brain and Chronic Post-Traumatic Headache: Implications for its Mechanism

“…43 The two former are particularly relevant, because the clinical features of CPTHA resemble those of primary headaches. Lack of habituation of somatosensory evoked potentials [44][45][46][47] and the blink reflex 48 was also found among individuals with primary headache. The correlation found herein between the magnitude of CPTHA and the magnitude of pain adaptation and CPM does not provide causality.…”

What has functional neuroimaging done for primary headache … and for the clinical neurologist?

“…79 Patients with migraine have increased LEPS amplitudes in comparison to healthy controls and habituation to painful stimuli and other sensory stimuli is reduced in these patients. [80][81][82] Amplitudes of contingent negative variation related to attention and arousal are increased in migraine patients, which indicates hypervigilance in these patients and which can be explained by delayed habituation. 83,84 Impaired pain perception with decreased pain thresholds due to a dysfunction of pain control systems might also have a role in cluster headache.…”