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Is the cerebral cortex hyperexcitable or hyperresponsive in migraine?

Authors

  • G Coppola,

    1. G.B. Bietti Eye Foundation-IRCCS, Department of Neurophysiology of Vision and Neurophthalmology,
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  • F Pierelli,

    1. University of Rome ‘La Sapienza’ Polo Pontino—I.C.O.T., Rome and
    2. IRCCCS-Neuromed, Pozzilli (IS), Italy,
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  • J Schoenen

    Corresponding author
    1. Headache Research Unit, University Department of Neurology and
    2. Research Centre for Cell and Molecular Neurobiology, Liège University, Liège, Belgium
      Professor Jean Schoenen, University Department of Neurology, CHR Citadelle, Bld. du 12ème de Ligne 1, B-4000 Liège, Belgium. Tel. + 32 4 225 6391, fax + 32 4 225 6451, e-mail jean.schoenen@chrcitadelle.be
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Professor Jean Schoenen, University Department of Neurology, CHR Citadelle, Bld. du 12ème de Ligne 1, B-4000 Liège, Belgium. Tel. + 32 4 225 6391, fax + 32 4 225 6451, e-mail jean.schoenen@chrcitadelle.be

Abstract

Although migraineurs appear in general to be hypersensitive to external stimuli, they maybe also have increased daytime sleepiness and complain of fatigue. Neurophisiological studies between attacks have shown that for a number of different sensory modalities the migrainous brain is characterised by a lack of habituation of evoked responses. Whether this is due to increased cortical hyperexcitability, possibly due to decreased inhibition, or to an abnormal responsivity of the cortex due a decreased preactivation level remains disputed. Studies using transcranial magnetic stimulation in particular have yielded contradictory results. We will review here the available data on cortical excitability obtained with different methodological approaches in patients over the migraine cycle. We will show that these data congruently indicate that the sensory cortices of migraineurs react excessively to repetitive, but not to single, stimuli and that the controversy above hyper- versus hypo-excitability is merely a semantic misunderstanding. Describing the migrainous brain as ‘hyperresponsive’ would fit most of the available data. Deciphering the precise cellular and molecular underpinnings of this hyperresponsivity remains a challenge for future research. We propose, as a working hypothesis, that a thalamo-cortical dysrhythmia might be the culprit.

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