Tempromandibular Disorders and Related Pathologies

Temporomandibular disorders (TMD) is one of the most common syndromes that reflects deep somatic pain. The origin of the pain in TMD lies in masticatory and cervical muscles, and the temporomandibular joint (TMJ). Unaware tooth contact during day- and nighttime leads to sustained masticatory muscle contraction and it results in muscular pain. This tooth contact is not necessarily accompanied by bruxism and it elicits mild tension of masticatory muscles. The most cases of TMJ internal derangement are caused by masticatory muscle contraction, too. Muscle fatigue that is caused by sustained muscle contraction elicits noxious input and it leads to central sensitization and neuronal plasticity of the secondary neurons in the subnucleus caudalis of the trigeminal spinal nucleus. This change in the central nervous system results in referred pain. Behavioral therapy such as relaxation and stretch of the masticatory muscles is essential for the remission of symptoms. Neither pharmacotherapy except for a few medicines (e.g., NSAIDs with benzodiazepines and tricyclic antidepressants) nor splint therapy is supported by systematical reviews. Trigger point injection with both local anesthetics and normal saline provides significant pain relief. Deep somatic pain originates not only from the masticatory muscles or the TMJ, but also from surrounding structures. Sustained noxious imputs from extra- and intracranial vasculature, jaw bones, cervical muscles, vertebrae, sinuses, nose, eyes and ears may cause referred pain in the orofacial region. Orofacial pain is occasionally seen as a sign of migraine. Maxillary molar toothache and TMJ pain are more frequently observed in cluster headache. Tension type headache may be associated with TMD. These headaches appear with their specific accessory symptoms. TMJ pain that lasts several hours to a couple of days and concomitant nausea, vomiting, photo- and phonophobia should be investigated for migraine. Pain around the TMJ and upper molars with ipsilateral lacrimation, eyelid edema, conjunctival injection of the eyeball and nasal congestion may be signs of cluster headache. Some autoimmune diseases resemble TMD. Sjögren syndrome may accompany pain in the preauricular (parotid gland) region. Temporal arteritis is associated with trismus due to severe pain in the temple and the TMJ. Laboratory data will be a help to make a differential diagnosis in these conditions. Paroxysmal neuralgias (e.g., trigeminal and glossopharyngeal neuralgias) may elicit pain precipitation during the jaw movement. Trigger zones should be explored in the territories of affected nerves, although sometimes it is difficult to make a definitive diagnosis. Paroxysmal neuralgias usually do not cause pain every time the jaw moves, while muscular and joint problems always do. The pain of TMD is classified into the deep somatic pain and other conditions of the same classification, neuropathic pain (paroxysmal neuralgias) and psychiatric diseases (somatoform disorders, depression, etc.) should be differentially diagnosed.