What is craniofacial pain and the mechanisms underlying craniofacial pain? Craniofacial pain is pain in the head, neck, and face, caused by issues like jaw problems (e.g., TMD), teeth grinding (bruxism), poor posture, and trauma. Symptoms include facial, ear, or neck pain and may be triggered by touch, stress, or fatigue. Treatment varies depending on the cause but can include dental appliances, physical therapy, managing stress, and sometimes surgical interventions for severe cases. Craniofacial pain mechanisms involve both peripheral and central nervous system changes, particularly in chronic conditions like migraines and temporomandibular disorders (TMD). Peripheral mechanisms include the sensitization of nerve fibers, while central mechanisms involve altered activity in the brainstem and brain regions like the thalamus. Chronic pain is often sustained by changes that amplify pain signals through mechanisms like nerve hyperexcitability, altered modulatory pathways, and changes in brain structure. Peripheral mechanisms Sensitization of peripheral afferents: Nociceptive (pain-sensing) nerve fibers in the face and head can become sensitized, leading to a lower threshold for activation and increased pain signals. TRP channels and glutamate receptors: In conditions like TMD, receptors like transient receptor potential (TRP) channels and glutamate receptors in muscles can be activated by inflammatory mediators and other substances, contributing to muscle pain and hypersensitivity. Neuroinflammation: In response to injury or inflammation, non-neural cells like microglia and macrophages in the central nervous system can become activated, releasing signaling molecules that enhance neuronal hyperexcitability. Central mechanisms Central sensitization: Repeated or intense pain signals can lead to changes in the central nervous system, such as hyperexcitability of central neurons, which amplifies pain signals. Changes in brain structure: Chronic craniofacial pain is associated with physical changes in the brain, which can amplify pain perception. Altered descending pain modulation: The balance of descending pain modulatory systems can be disrupted, leading to an imbalance that allows pain signals to persist. Convergence and referral: Nerve fibers from different areas, like the face and neck, can converge on the same neurons in the brainstem. This can cause referred pain, where pain is felt in one area (e.g., the face) but originates in another (e.g., a neck muscle). Specific examples Trigeminal neuropathies: Pain conditions caused by damage to the trigeminal nerve. The mechanism involves changes in the activity of neurons in the trigeminal nucleus and surrounding spinal cord regions. Migraine: Migraine pain involves complex mechanisms in both the peripheral trigeminal system and the central nervous system, including activation of trigeminal nerves and changes in brain activity