Correlation between Functional Magnetic Resonance and Symptomatologic Examination in Adult Patients with Myofascial Pain Syndrome of the Masticatory Muscles

Myofascial pain syndrome is the most common cause of TMD, characterised by trigger points of skeletal muscles in the masticatory region. Patients with myofascial pain suffer from orofacial pain and headaches. Parafunctional activity such as unconscious teeth clenching predisposes a higher possibility of developing myofascial pain. We report the results of a prospective study of 10 patients with a myofascial pain diagnosis related to TMD who underwent treatment with passive aligners and biofeedback exercise. All patients underwent pain assessment (visual analogic scale and muscular palpation test), measurement of masseters thickness with Dolphin Imaging Software, nuclear magnetic resonance of the temporomandibular joint, and functional nuclear magnetic resonance of the brain before and after gnathological treatment. The same patients underwent pain assessment (VAS and palpation test) for the entire duration of their treatment. This study aimed to assess if the results obtained with the therapy were repeatable using functional magnetic resonance imaging. This enabled us to correlate a subjective datum (pain) to an objective one (variation in the functional connectivity of the networks correlated to pain perception). According to the pain assessment, the treatment considerably reduced the pain in 9 out of 10 patients. Furthermore, the functional nuclear magnetic resonance of the brain showed similar modifications in the cerebral pain and default mode networks in these nine patients. The change in the masseter muscle dimensions was not correlated with the modification of pain. Statistical analysis was performed to evaluate the effects of treatment on VAS and trigger point stimulation and on the length and width of the masseter muscle. Linear regression analysis was used to assess a correlation between the modification of the masseter muscle dimension and the amendment of VAS. A paired t-test was used to evaluate statistically significant differences in the connectivity of brain areas of the DMN and the pain network. Our results suggest that the proper treatment of myofascial pain can reduce pain and consistently modify the functional activation of the cerebral pain and default mode networks. Overall, the treatment was repeatable because brain network changes were homogeneous in all patients and did not relate to the intracapsular TMJ condition but only to pain symptoms.