Patients with temporomandibular disorders and chronic pain of myofascial origin display reduced alpha power density and altered Small-world properties of brain networks

Chronic pain is one of the most common symptoms of temporomandibular disorders (TMD). Although its pathophysiology is still a challenge, TMD has been associated with changes in central nervous system activity related to pain modulatory capacity. This study was conducted to examine the cortical activity of patients with temporomandibular disorders and chronic pain of myofascial origin using quantitative electroencephalography (qEEG). Individuals with TMD and chronic pain and healthy controls were evaluated using qEEG in four consecutive conditions, all with closed eyes: 1) initial resting condition; 2) non-painful motor imagery task of hand movement; 3) painful motor imagery task of clenching the teeth; 4) final resting condition. Participants with TMD and chronic pain overall presented decreased alpha power density during baseline at rest, and non-painful and painful motor imagery tasks when compared to healthy controls. Furthermore, functional brain connectivity was distinct between groups, with TMD and chronic pain showing lower small-world values for the delta (all conditions), theta (eyes closed, painful and non-painful motor imagery task), and alpha bands (painful motor imagery task), and an increase in the beta band (all conditions). These results suggest that TMD and related chronic pain is associated with maladaptive plasticity in the brain, which may correspond to a reduced ability to modify brain activity during different mental tasks, including painful and non-painful imagery. These changes can be detected by qEEG, a method which may be very important because of its characteristics of good temporal resolution and the possibility to be performed in naturalistic setups.