[Nociception and chronic oral and cervicofacial pain]

This short review focuses on the main properties of the nervous system responsible for pain originating from oral, nasal and pharyngeal cavities. First, the major roles of the somatic sensations coming from the orofacial and pharyngeal areas are emphasized. Then, the description of the respective peripheral fields of the different cranial nerves involved in these somatic sensations is followed by the description of the primary afferent neurons and the central nuclei and pathways. The review emphasizes that pain does not result from a simple transmission of nervous impulses that would follow a fixed "hardwire" pathway but, on the contrary, results from an ever-changing balance between excitatory and inhibitory influences. These descending influences and other mechanisms may lead acute pain to become chronic through plastic changes of the nervous system and possible neuropathic changes. Finally, certain psychosocial factors that may facilitate chronic pain arousal are discussed.