Reduced habituation to experimental pain in migraine patients: a CO2 laser evoked potential study

Abstract

The habituation to sensory stimuli of different modalities is reduced in migraine patients. However, the habituation to pain has never been evaluated. Our aim was to assess the nociceptive pathway function and the habituation to experimental pain in patients with migraine. Scalp potentials were evoked by CO(2) laser stimulation (laser evoked potentials, LEPs) of the hand and facial skin in 24 patients with migraine without aura (MO), 19 patients with chronic tension-type headache (CTTH), and 28 control subjects (CS). The habituation was studied by measuring the changes of LEP amplitudes across three consecutive repetitions of 30 trials each (the repetitions lasted 5 min and were separated by 5-min intervals). The slope of the regression line between LEP amplitude and number of repetitions was taken as an index of habituation. The LEPs consisted of middle-latency, low-amplitude responses (N1, contralateral temporal region, and P1, frontal region) followed by a late, high-amplitude, negative-positive complex (N2/P2, vertex). The latency and amplitude of these responses were similar in both patients and controls. While CS and CTTH patients showed a significant habituation of the N2/P2 response, in MO patients this LEP component did not develop any habituation at all after face stimulation and showed a significantly lower habituation than in CS after hand stimulation. The habituation index of the vertex N2/P2 complex exceeded the normal limits in 13 out of the 24 MO patients and in none of the 19 CTTH patients (P<0.0001; Fisher's exact test). Moreover, while the N1-P1 amplitude showed a significant habituation in CS after hand stimulation, it did not change across repetitions in MO patients. In conclusion, no functional impairment of the nociceptive pathways, including the trigeminal pathways, was found in either MO or CTTH patients. But patients with migraine had a reduced habituation, which probably reflects an abnormal excitability of the cortical areas involved in pain processing.

Visual evoked potentials in migraine: Is the “neurophysiological hallmark” concept still valid?

“…This interpretation is in line with numerous evoked potential studies that have applied similar protocols (e.g. Afra et al, 1998;Ambrosini et al, 2003;Brodsky et al, 2013;Chen et al, 2009;Coppola et al, 2013b;Ozkul and Uckardes, 2002;Sand et al, 2008;Schoenen et al, 1995;Siniatchkin et al, 2006;Valeriani et al, 2003). The present study did not aim to investigate if the amplitude decline during VEP stimulation is caused by habituation in the central nervous system.…”

Effects of remote cutaneous pain on trigeminal laser-evoked potentials in migraine patients

“…In migraine patients, the LEP features and the laser pain intensity in basal conditions were similar to those in nonmigraine subjects, according to previous studies [2,9,10]. During capsaicin application, the LEPs and laser pain were not modified at both the sites of examination, with respect to the pre-and post-capsaicin condition, despite a clear painful sensation being perceived on the left hand.…”

“…In recent years we have performed some studies of LEPs in migraine. The most evident abnormalities consisted of a reduced habituation to repetitive stimuli [9], and a reduced inhibiting effect induced by distraction [2]; in addition, trigeminal LEPs did not appear inhibited during homotopical experimental pain [10]. In normal subjects, the LEPs obtained by limb and cervical dermatomal stimulation appeared suppressed by heterotopical noxious stimulation, for the effect of DNIC [11][12][13].…”

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.…”