tDCS for the Treatment of Migraine

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.

this is a questionnaire, composed of six questions, developed to measure the impact of headache on daily living activities of individuals with chronic episodic and migraine. It is a valid and reliable instrument for this population and its results are related to clinic parameters of migraine, e.g. severity and quality of life. Total score ranges from 36 to 78 and it is categorized into four levels: slight or no impact (38 to 49 points); some impact (50 to 55 points); substantial impact (56-59 points); very severe impact (60 or more points). The minimum important difference for this scale was estimated at -2.5 to -5.5 points (within groups) and -1.5 points (between groups).

this is a questionnaire, composed of five items, created to evaluate disability caused by headache in a period of 3 months. This instrument is reliable and validated in several countries, and its Portuguese version may be used to identify severe cases of migraine. MIDAS total score will be obtained by adding days lost in each of the areas being categorized into four levels: slight or none disability (0 to 5 days); mild disability (6 to 10 days); moderate disability (11 to 20 days); intense capacity (≥21 days).

this scale will be used to measure the patients' pain intensity. VAS is an important instrument to verify, reliably, the patient's evolution during treatment. This scale will be used at beginning and end of each period (observation and treatment), before and after each tDCS session. For the VAS use, pain intensity will be asked to the patient. 0 cm means total pain absence and 10 cm is the level of maximum pain bearable by the patient.

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 transcranial magnetic stimulation (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.

to evaluate these variables, 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). The Intracortical facilitation (ICF) will be evaluated by the MEP average at an ISI of 10 milliseconds. Ten stimulus will be applied in each condition (unconditioned pulse, and pairs of stimuli with ISI of 2 and 10 milliseconds). The order of stimulus delivered will be pseudorandomized and SICI and ICF will be expressed as a percentage of a conditioned stimuli in regarding an unconditioned stimuli.

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.