The aim of this study is to investigate the motor and visual cortex excitability in response to visual stimulation of migraineurs with and without aura compared to healthy individuals. For this purpose, electrical cortical activity of migraineurs will be compared to healthy volunteers.
A cross sectional study to compare the best approach to migraineurs evaluation. For this, healthy individuals, after reading and signing the free and informed consent will be submitted to a single session to obtain the normal neurophysiological endpoints and thus compare with those obtained in individuals with migraineurs volunteers. All volunteers (healthy and migraineurs) will be submitted to a neurophysiological evaluation through transcranial magnetic stimulation (TMS) and electroencephalography (EEG). A visual stimulation will be delivered during the assessment of habituation through visual evoked potential volunteers (VEP-habituation) and the following measures will be evaluated before and after visual stimulation: (i) Motor Evoked Potentials (MEP); (ii) Motor Threshold (MT); (iii) Short Interval Cortical Inhibition (SICI); (iv) Intracortical Facilitation (lCF) and (v) Phosphene Threshold (PT).
Study Type
OBSERVATIONAL
Enrollment
59
volunteers will be invited to sit in a comfortable chair, in a calm and dark room, at 90 cm of distance from computer screen. It will be asked to fix his right eye visual field on a red point at the center of the screen (the left one will be blindfolded). Visual stimuli will be a black and White grid pattern, alternating at a frequency of 3.1 Hz.
Laboratório de Neurociência Aplicada (LANA)
Recife, Pernambuco, Brazil
Changes on motor evoked potentials
to measure MEP, the intensity of the magnetic stimulator will be adjusted to 120% of rest motor threshold and 10 stimuli will be registered. For evaluation volunteers will be instructed to sit in a chair and get into a comfortable position. Initially, single-pulse TMS will be administered over the motor cortex to determine the cortical representation area of the first dorsal interosseous muscle (FDI). For all evaluations the same figure-eight coil is used, in order to avoid measurement bias. Amplitude means of evoked potentials will determine the MEP.
Time frame: one day (Before and after visual stimulation)
Changes on short interval intracortical inhibition
to evaluate this variable, subthreshold conditioning stimuli (80% of RMT) and suprathreshold test stimuli (120% of RMT) will be delivered at an inter stimulus intervals (ISI) of 2 milliseconds, to determine the short interval cortical inhibition (SICI). Ten stimuli will be applied in each condition (unconditioned pulse and pairs of stimuli with ISI of 2 milliseconds). The order of stimulus delivered will be pseudorandomized and SICI will be expressed as a percentage of a conditioned stimuli in regarding an unconditioned stimuli.
Time frame: one day (Before and after visual stimulation)
Changes on intracortical facilitation
to evaluate intracortical facilitation (ICF), subthreshold conditioning stimuli (80% of RMT) and suprathreshold test stimuli (120% of RMT) will be delivered at an inter stimulus intervals (ISI) of 10 milliseconds. Ten stimulus will be applied in each condition (unconditioned pulse and pairs of stimuli with ISI of 10 milliseconds). The order of stimuli delivered will be pseudorandomized and ICF will be expressed as a percentage of a conditioned stimuli in regarding an unconditioned stimuli.
Time frame: one day (Before and after visual stimulation)
Changes from phosphene threshold
a 10-cm circular coil was used that has giving a peak magnetic field strength of 2 tesla. Subjects were asked to wear a blindfold, sit comfortably in a chair and to close their eyes to diminish ambient light.In sagittal line, three points were scored: 2, 3 and 4 cm above the inion. The single pulse TMS was applied to one of the points scored and the subject was asked to report the presence or absence of a phosphene immediately after stimulation. The stimulation was repeated ten times at each intensity with a maximum frequency of 0.2 Hz, stimulation was initially applied to 60% of the maximum intensity of the stimulator. The intensity of stimulation was changed into blocks of 5% to minimum intensity that the subject can perceive the phosphene certainly, five times ten, then this value was set as the PT.
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Time frame: one day (Before and after visual stimulation)
Habituation of Visual Evoked Potentials evaluated by Electroencephalography
volunteers will be invited to sit in a comfortable chair, in a calm and dark room, at 90 cm of distance from computer screen. It will be asked to fix his right eye visual field on a red point at the center of the screen (the left one will be blindfolded). Visual stimuli will be a black and White grid pattern, alternating at a frequency of 3.1 Hz. Electrodes used to record data will be localized on Oz and Fz points according International 10-20 system. During the test, 600 cortical answers will be recorded. Data will be collected and recorded in a personal computer, and after, converted to the ".txt" format to futures analysis with MATLAB.
Time frame: one day (during visual stimulation)