title: Persistent ictal-like visual cortical excitability in chronic migraine.
abstract: Episodic migraine (EM) may evolve into the more disabling chronic migraine (CM, monthly migraine days ≥ 8 and headache days ≥ 15) with unknown mechanism. Aiming to elucidate the pathophysiology of CM and its relationship with EM, this study characterized the visual cortical responses in CM and EM. Neuromagnetic visual-evoked responses to left-hemifield checkerboard reversals were obtained in patients with EM (interictal or ictal states), CM (interictal) and age-matched controls. For each subject, the 1500 evoked responses were sequentially divided into 30 blocks and percentage changes of P100m amplitude in blocks 2, 9, 16, 23, and 30 compared to the first block were computed to assess habituation. At the end of visual stimulation (block 30), P100m amplitude was decreased (habituated) in the controls (n=32) (35.2±2.6nAm vs. 41.9±2.7, p=0.005) but increased (potentiated) in the interictal state of EM (n=29) (39.7±3.8 vs. 33.5±3.0, p=0.007). In CM (n=25), P100m was habituated (46.5±2.9 vs. 51.6±3.7, p=0.013) but higher at the initial block than in those of the interictal state of EM (p=0.001). These CM features also characterized the P100m in the ictal state of EM (n=9). There was no difference of P100m between CM and ictal state of EM. In conclusion, patients with CM demonstrate a persistent ictal-like excitability pattern of the visual cortex between migraine attacks which may implicate central inhibitory dysfunction.
authors.affiliation: Department of Neurology, Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan School of Medicine, National Yang-Ming University, Taipei, Taiwan Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan Institute of Neuroscience, National Yang-Ming University, Taipei, Taiwan Department of Ophthalmology, Taipei Veterans General Hospital, Taipei, Taiwan Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Wei-Ta
authors.initials: WT
authors.lastname: Chen
authors.forename: Shuu-Jiun
authors.initials: SJ
authors.lastname: Wang
authors.forename: Jong-Ling
authors.initials: JL
authors.lastname: Fuh
authors.forename: Ching-Po
authors.initials: CP
authors.lastname: Lin
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Ko
authors.forename: Yung-Yang
authors.initials: YY
authors.lastname: Lin
mesh_terms: D000328:Adult; D002908:Chronic Disease; D020937:Epilepsy, Partial, Sensory / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D006801:Humans; D008297:Male; D008881:Migraine Disorders / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D014793:Visual Cortex / Q000503:physiopathology*; D055815:Young Adult