High-Definition and Non-invasive Brain Modulation of Pain and Motor Dysfunction in Chronic TMD

Background: Temporomandibular disorders (TMD) have a high prevalence and in many patients pain and masticatory dysfunction persist despite a range of treatments. Non-invasive brain neuromodulatory methods, namely transcranial direct current stimulation (tDCS), can provide relatively long-lasting pain relief in chronic pain patients.

Objective: To define the neuromodulatory effect of five daily 2x2 motor cortex high-definition tDCS (HD-tDCS) sessions on clinical pain and motor measures in chronic TMD patients. It is predicted that M1 HD-tDCS will selectively modulate clinical measures, by showing greater analgesic after-effects compared to placebo, and active treatment will increase pain free jaw movement more than placebo.

Methods: Twenty-four females with chronic myofascial TMD pain underwent five daily, 20-min sessions of active or sham 2 milliamps (mA) HD-tDCS. Measurable outcomes included pain-free mouth opening, visual analog scale (VAS), sectional sensory-discriminative pain measures tracked by a mobile application, short form of the McGill Pain Questionnaire, and the Positive and Negative Affect Schedule. Follow-up occurred at one-week and four-weeks post-treatment.

Results: There were significant improvements for clinical pain and motor measurements in the active HD-tDCS group compared to the placebo group for: responders with pain relief above 50% in the VAS at four-week follow-up (P = 0.04); pain-free mouth opening at one-week follow-up (P < 0.01); and sectional pain area, intensity and their sum measures contralateral to putative M1 stimulation during the treatment week (P < 0.01). No changes in emotional values were shown between groups.

Conclusion: Putative M1 stimulation by HD-tDCS selectively improved meaningful clinical sensory-discriminative pain and motor measures during stimulation, and up to four-weeks post-treatment in chronic myofascial TMD pain patients.