Evaluation of the Efficacy of Neuromodulation in the Control of Chronic Orofacial Pain: A Randomized Controlled Trial
Evaluation of the Efficacy of Neuromodulation in the Control of Chronic Orofacial Pain: A Randomized Controlled Trial
Chronic orofacial pain significantly affects patients' quality of life, compromising essential functions such as chewing and speech. Although conventional treatments are available, many patients do not achieve adequate and lasting relief. This project investigates the effectiveness of neuromodulation techniques, namely transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS), as innovative therapeutic alternatives for the control of chronic orofacial pain.
The study will be conducted in adult patients diagnosed with orofacial pain. Participants will be divided into two groups: one group will receive active neuromodulation (tDCS or TMS) and the other a sham treatment (placebo). Sessions will take place daily over two weeks. Assessments will include pain intensity, pain pressure threshold, masticatory function, and bite strength, in order to observe any functional changes.
The group undergoing neuromodulation is expected to show a significant reduction in pain levels and improvements in quality of life compared to the placebo group. This study could support the adoption of neuromodulation as a complementary approach in the treatment of chronic orofacial pain, offering an effective and non-invasive alternative for patients who do not respond to conventional treatments.
The study will be conducted at the University Clinic of the Egas Moniz School of Health and Science - Department of Orofacial Pain. The objective is to evaluate the effects of electrical and magnetic neuromodulation on different chronic pain conditions using standardized non-invasive brain stimulation protocols and validated clinical and functional assessment instruments.
Sample
Individuals with chronic low back pain (score between 40 and 80 on the Portuguese version of the Oswestry Disability Index) and chronic orofacial pain (score between 40 and 80 on the Portuguese version of the Manchester Orofacial Pain Disability Scale) will be selected.
For each chronic pain condition, 50 individuals will be enrolled and allocated into two groups: a control group and an intervention group.
Inclusion Criteria
Age between 18 and 75 years.
Diagnosis of chronic orofacial pain lasting longer than 3 months, confirmed by validated diagnostic criteria such as DC/TMD.
Initial Visual Analogue Scale (VAS) score ≥ 4.
Previous attempt of at least one conventional treatment with limited effectiveness.
Cognitive capacity sufficient to understand study procedures and provide informed consent.
Stable chronic pain medication regimen for at least four weeks prior to the intervention.
Exclusion Criteria
History of epilepsy, seizures, or other neurological conditions that contraindicate tDCS or TMS.
Presence of implanted medical devices, including pacemakers, cochlear implants, or other electronic/metallic devices in the head or neck region.
Pregnancy or breastfeeding.
Severe psychiatric disorders that may compromise adherence to study procedures.
Current or recent history (within the last six months) of alcohol or substance abuse.
Active infections or untreated systemic diseases that may interfere with the intervention or outcomes.
History of temporomandibular joint surgery or recent invasive dental procedures (within the last three months).
Known contraindications to TMS or tDCS, including intolerance to neuromodulation.
Participation in another clinical trial within the last three months.
Randomization
Participants will be randomly allocated to the control or intervention group by an independent investigator using an electronic randomization tool (Research Randomizer). Allocation will remain concealed until completion of assessments.
Sample Size Calculation
Sample size estimation indicates the need for 15 participants per group to ensure a statistical power of 85% (β = 0.20) and a significance level of p < 0.05. The final sample size was expanded to enhance the robustness of statistical analyses and to compensate for potential dropouts.
Assessment Instruments Visual Analogue Scale (VAS)
A 0-10 numerical scale used to quantify pain intensity, where 0 indicates no pain and 10 represents the worst imaginable pain.
Brief Pain Inventory (BPI)
A multidimensional tool that assesses pain intensity and pain interference with daily activities over the past 24 hours.
Graded Chronic Pain Scale (GCPS)
A scale that classifies chronic pain into severity grades based on pain intensity and functional disability.
SF-36 Health Survey
A generic quality-of-life questionnaire comprising 36 items distributed across eight domains, with scores ranging from 0 (worst health status) to 100 (best health status).
Manchester Orofacial Pain Disability Scale
An instrument that measures functional disability associated with orofacial pain, focusing on daily activities such as chewing and speaking.
Pressure Pain Threshold (PPT)
Assessed using a portable algometer. The minimum pressure that elicits a painful sensation will be recorded. Each site will be measured twice, and the mean value will be used for analysis.
Intervention Transcranial Direct Current Stimulation (tDCS)
tDCS will be administered using 35 cm² electrodes for 20 minutes across five consecutive days. The anode will be positioned at C3 or C4, contralateral to the primary site of pain, according to the international 10-20 EEG system. The control group will receive sham stimulation with identical electrode placement and procedures.
Transcranial Magnetic Stimulation (TMS)
TMS will be delivered in 10 sessions over two weeks. The intervention group will receive active stimulation, while the control group will receive sham stimulation. Stimulation parameters (frequency, intensity, and coil placement) will follow standardized clinical research guidelines for chronic pain.
Inclusion Criteria:
Exclusion Criteria: