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

Abstract

Please cite this article as: Omland, P.M., Uglem, M., Hagen, K., Linde, M., Tronvik, E., Sand, T., Visual evoked potentials in migraine: Is the "neurophysiological hallmark" concept still valid ?, Clinical Neurophysiology (2015), doi: http://dx.doi.org/10. 1016/j.clinph.2014.12.035 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. • Lack of VEP habituation is not a reliable "neurophysiological hallmark" in interictal migraine• Strict focus on methodology, including blinding during the recording and assessment of VEP, is important to avoid overestimation of effect sizes in future studies.2 Abstract Objective Lack of habituation is considered a neurophysiological hallmark of migraine. However, the results of visual evoked potential (VEP) studies have been discrepant, possibly because of different stimulation parameters and lack of blinding. Hence, there is a need for independent confirmation of lack of VEP habituation in migraine. In this blinded study we applied 16' checks to supplement our previous findings with 8', 31', 62' and 65' checks. MethodsVEPs in 41 interictal migraineurs and 30 controls were compared. VEPs were recorded in six blocks of 100 single responses. Linear N70-P100 amplitude change over blocks (habituation slope) was compared with an independent samples Student's t-test. ResultsAmplitude decline over blocks was observed in both groups. Habituation slope was not significantly different between controls (-0.43 ± 0.54 μV/block) and migraineurs (-0.29 ± 0.35 μV/block) (p = 0.33). ConclusionVEP habituation with 16' checks did not differ in migraineurs and controls. This is in agreement with previous findings with other stimulation parameters. It is therefore unlikely that use of different stimulation parameters could explain the discrepant results of previous studies. No studies that applied blinding during recording of VEP have found lack of habituation in migraineurs. SignificanceLack of VEP habituation cannot be considered a reliable neurophysiological hallmark in migraine.

Habituation or lack of habituation: What is really lacking in migraine?

“…Moreover, given this criticism, how can we still mention habituation defect as a neurophysiological hallmark of migraine? This is indeed the position expressed in the paper by Omland et al (2015) published in this issue of Clinical Neurophysiology. Here authors study habituation to VEP in normal subjects and in patients with migraine using visual stimuli of 16 0 size to complete the series of check sizes explored in previous studies (8 0 , 31 0 , 62 0 , 65 0 ).…”

“…Should we now consider instead the chance that lack of habituation would simply be the result of a methodological bias? From the evidence reported and reviewed by Omland et al (2015) and Sand (2014) it would seem so or at least that a serious criticism should be raised about. However, important caveats exist and deserve mention.…”

“…However, important caveats exist and deserve mention. First of all, as stated also by Omland et al (2015), the criticism about habituation impairment should be confined to visual sensory modality because the contrary evidence is till now limited to VEP studies. Moreover, a multiplicity of factors, other than blinding, can affect recording of evoked potentials and consequently the ability to explore habituation and its impairment in migraine.…”

“…that, instead of blinding, differences in some of the other mentioned factors between ''pro'' and ''cons'' studies, could have hampered the emergence of a true habituation defect in migraine. Omland et al (2015) in their paper accurately present and discuss these patient-and procedure-related variables. As mentioned above, no role seems to be played by procedure-related factors concerning stimulation parameters (check size and stimulation frequency) because a wide range of such parameters (including those used in studies reporting habituation impairment in migraine) have been employed by the Omland and Sand group.…”

Migraine triggers and habituation of visual evoked potentials

“…This finding is noteworthy for the long-standing debate about the variability of VEP habituation in migraine. While fluctuations over the migraine cycle likely account for intra-subject variability, there is no unanimously accepted explanation for the between-subject differences (8,9). It has been shown that stress is able to increase event-related potentials by decreasing habituation to a greater degree in migraine patients than in healthy subjects (10), and just before a migraine attack (11).…”