A Review of the Relationship between Mild Traumatic Brain Injury, Post-Traumatic Stress Disorder, and Temporomandibular Disorder

Mild traumatic brain injuries (MTBI) and the development of post-traumatic stress disorder (PTSD) have become the signature injuries of those returning from the Middle East theatre of conflict. PTSD, MTBI, and temporomandibular disorders (TMD) are statistically associated and share many common symptoms including depression and myofascial pain. PTSD, MTBI, and TMD also share physiological and neurochemical similarities including NMDA receptor site activation. A chemical cascade follows a MTBI, releasing excessive neurotransmitters, causing secondary injury, central sensitization, and alteration of the HPA axis. PTSD is accompanied by physiological changes within the brain including HPA axis alteration, central sensitization, increased neurotransmitter sensitivity, and neuroplastic changes. Chronic TMD patients may also suffer from central sensitization and altered HPA axis function. Measurable physiologic parameters for HPA axis and sympathetic/parasympathetic autonomic balance include heart rate variability and salivary cortisol. With increasing numbers of war veterans returning to the United States suffering the effects of PTSD, MTBI, and TMD, providers need to be aware of the common underlying processes when faced with identically presenting patients.