THE EFFECT OF TRANSCRANIAL DIRECT CURRENT STIMULATION (tDCS) IN THE TREATMENT OF CHRONIC PELVIC PAIN ASSOCIATED WITH ENDOMETRIOSIS

Changes in motor cortex blood flow assessed by near infrared spectroscopy

时间窗: Treatment Day 1 (before receiving the 1st session of tDCS); Day 15 (at the end of treatment period) and Day 29 (at the end of follow-up period)

Motor cortex blood flow will be assessed before the first session of tDCS (on Treatment day 1), after the end of treatment period (Day 15) and after the follow-up period (Day 29). Total = 3 evaluations.

Change in the temperature pain threshold

时间窗: up to Day 29

It will be assessed by the Quantitative Sensory Test (QST) in the dominant (right) forearm. The heat pain tolerance and pain threshold to the heat and the temperature defined as pain 6/10 by the participant. The temperature starts at 32°C, and it heat at a 1.0 °C/sec rate and cools down after a button is pressed or whenever it reaches the max temperature of 52°C. The participant will be asked to press the button at the first sensation of pain to determine the pain threshold; to press the button whenever she can not stand the heat anymore for the pain tolerance determination and, for last, to press the button at the temperature she fells pain equivalent to 6/10 in the numeric scale of pain. The pain threshold and the temperature of pain 6/10 will be determined by the arithmetic mean of 3 evaluations each. Total of 3 test days: Day 1 (before the first session of tDCS), after the end of the Treatment period (Day 15) and at the end of the follow-up period (Day 29).

Change in effect of the descendent modulator system of pain

时间窗: up to Day 29

It will be assessed by the Conditioned Pain Modulation test (CPM). A nociceptive tonic conditioning stimulus - immersion of the non-dominant hand in cold water (0°C for 1 minute) - will be applied concomitant to the progressive thermal stimulus in the dominant forearm as applied in the QST pattern until it reaches the 6/10 pain temperature previously determined by the participant. It will be tested in Treatment Day 1 (before the first session of tDCS - considered baseline), after the end of the Treatment period (Day 15) and at the end of the follow-up period (Day 29) - Total = 3 evaluation.

Change in worst daily pain assessed with the visual analogue scale.

时间窗: Once Daily. Start 7 days before treatment, everyday during treatment period and every day during follow-up period (total = 35 days)

Patients will be asked to daily write down their worst pain level (assessed by the Visual Analogue Scale, self-administered) in a paper diary with different scores: global pain, pain during menses, pain during sexual intercourse, pain during urination, pain during defecation. They will also be asked to daily write the analgesic drug intake. Total evaluations: 35 days.

Change in Functional Pain Scale

时间窗: Once a week - Treatment Day 1, Day 8, Day 15, Day 22, Day 29

Functional Pain Scale will be assessed by the Brazilian Profile of Chronic Pain: Screen (B-PCP:S) once a week, as folow: On the Treatment Day 1 (before the first session of tDCS - considered baseline), on Treatment Day 8, Day 15, Day 22 and Day 29. Total = 5 evaluations.