Effect of Transcutaneous Electrical Nerve Stimulation (TENS) in Chronic Migraine

INTERVENTION: Device Thirty subjects are randomized into two study groups and submitted to 10 sessions of transcutaneous electrical nerve stimulation (TENS). TENS is applied to the upper trapezius region bilaterally using the Empi® device (St. Paul, MN, USA) for 30 minutes, with a pulse duration of 100 ?s and an alternating stimulation frequency between sessions using 4 Hz and 100 Hz. 1) Active TENS: Once TENS is applied, the stimulation intensity is gradually increased until strong muscle fibrillation occurs, but reported by the subject as subjectively comfortable. Every 5 minutes the intensity is increased again and a strong but comfortable sensation with muscle contraction is felt. 2) TENS Placebo: The internal circuit of the TENS emitting device has been modified by the manufacturer in order to modify the current release so that it is released only within the first 40 seconds of stimulation and then current flow is ceased. Transcutaneous Electric Nerve Stimulation CONDITION: Headache Migraine Disorders Migraine disorders, Headache ; Migraine Disorders ; Headache INCLUSION CRITERIA: Patients diagnosed with chronic aura and non‐aura migraine headache, with pain intensity equal to or greater than 4 on the numerical pain scale, both sexes and aged 18 to 59 years. PRIMARY OUTCOME: Conditioned Pain Modulation ‐ measured by PPT assessment using digital pressure algometer, positioned on the anterior face of the right forearm. Then, an ischemic compression is performed on the left arm of individual by means of a sphingmomanometer. A pressure of 270mmHg is maintained and PPT is measured again on the right forearm and then compression is removed. Five minutes after the end of procedure, the PPT is measured again. Frequency of migraine attacks ‐ measured by Migraine Disability Assessment (MIDAS) questionnaire. The subjects answer five questions, marking the number of days from the last three months in which their activities were limited due to headaches. After being answered, a sum of the values attributed by the subject to each question is made. The severity of the dysfunction is classified as: absent (0 ‐ 5 points), mild (6 ‐ 10 points), moderate (11 – 20 points) and severe (>21 points). Pain intensity ‐ measured by 11‐point numerical scale. Patients are asked to indicate a number, from 0 to 10 that represents the intensity of pain experienced, with 0 being considered as “no painâ€? and 10 as “unbearable intense painâ€?. Values of 1‐3 are considered as mild pain, from 4 to 6 (moderate pain), and from 7 to 10 (severe pain).This scale is being applied to measure pain at rest, during cervical movement and during algometric testing. Pressure pain threshold (PPT) ‐ assessed using a digital pressure algometer. With the patient lying down, the muscular bellies of the temporal, sternocleidomastoid, upper trapezius, frontal and masseter muscles are being bilaterally evaluated. In procedure, algometer must be positioned perpendicular to point to be examined, and a constant and increasing pressure is exerted until pain is accused. Three measurements are made at each pre‐established site before and after treatment and the mean between them are considered. Temporal Summation ‐ measured using a digital pressure algometer, where a pressure of 2.5 kg is applied to anterior face of the patient's right forearm. This test is performed in a continuous sequence of 30 seconds, in which four measurements are made at the 1st, 10th, 20th and 30th seconds, and pain intensity values are recorded at each of these moments, using 11‐points numerical scale. SECONDARY OUTCOME: Anxiety and depression symptoms ‐ measured by Hospital Anxiety and Depression Scale (HAD). It has 14 items, seven of which are for anxiety assessment (HAD‐A) and seven for depression (HAD‐D). Each item can score from 0 to 3 points, totaling 21 points, for each scale. The anxiety scale is assigned values of: no anxiety (0‐8 points) and anxiety (> 9 points). And for depression scale: no depression (0‐8 points) and with depression (> 9 points). HAD has shown good validity and reliability in individuals with headache. Catastrophizing pain ‐ measured by Pain Catastrophizing Scale. The questionnaire has thirteen items that deal with thoughts and feelings experienced when individual is in pain. The total score is fifty‐two points, where a score above twenty‐four indicates a high score. Cervical Disability ‐ measured by Neck Disability Index (NDI). It consists of ten items, and each alternative describes increasing degrees of interference from neck pain in performing activities. The final score is obtained by the sum of points of the items answered by subjects, which can total a maximum of 50 points. Severity of disability is classified as mild (5 ‐ 14 points), moderate (15 ‐ 24 points), severe (25 ‐ 34 points) and completely disabling (? 35 points). Cervical range of motion ‐ measured using a fleximeter whose scale is in degrees. Flexion, extension, right and left lateralization and right and left rotation movements are evaluated. For each movement, three repetitions are performed from which average is obtained. Kinesiophobia ‐ measured by Tampa Kinesiophobia Scale. It has a total of 17 items; each with scores ranging from 1 to 4. In the end, minimum score obtained can be 17 points and maximum score 68 points, and the higher score, greater the fear of moving due to pain. Quality of life ‐ measured by Medical Outcomes Study 36 Questionnaire ‐ Short Form Health Survey (SF‐36). This instrument consists of 36 items grouped into eight domains: functional capacity, physical aspects, pain, vitality, emotional and social aspects, mental health and general health. The final score ranges from zero to one hundred, which represents the worst state of health and the best state of health, respectively. Skin temperature ‐ Measured through an infrared camera. Initially, patients are acclimatized in a room with an average temperature of 21°C and relative humidity of 80% for 15 minutes. The image is performed on the head and neck, in following views: anterior, right lateral and left and posterior. The results are analyzed in camera software standardizing interest regions in muscles, which allow the average temperature of that region to be calculated.