Types and locations of pain In clinical practice, pain physicians often make a distinction between cancer pain and all other, nonmalignant pain. If the pain is nonmalignant, clinicians tend to describe it as belonging to one of three large categories: musculoskeletal (related to joints or muscles), cephalalgic (headache), or neuropathic (resulting from damage to or disease of the nerves themselves). The most common sources of chronic pain in the orofacial region are musculoskeletal pain (temporomandibular disorders), cephalalgic pain (headaches), neuropathic pain, and referred pain from other sources. Each will be discussed in some detail. Musculoskeletal pain Temporomandibular disorders cover a wide variety of painful and non-painful musculoskeletal conditions. The etiology of temporomandibular disorders is still unclear, but both macrotrauma, such as receiving a hit or blow to the face or a fall on the chin, and microtrauma, such as sustained or repetitive jaw posturing, biting nails or cheeks, or bruxism, are thought to play a definite role. There is still much debate about the possible role of occlusal relationships in the development and maintenance of temporomandibular disorders. The prevalence of masticatory muscle pain in the general population has been estimated to be as high as 13%, the prevalence of disc derangement has been estimated to be as high as 16%, and the prevalence of temporomandibular joint pain has been estimated to be as high as 9% (Chang et. al., 2018). The two common types of masticatory muscle pain are local myalgia , which means just what it says, local muscle pain, and myofascial pain , a term used when there are painful taut bands present in the muscle, which on palpation refer pain to other structures such as other muscles, or teeth. A well-known example of referred muscle pain is that of a myocardial infarction, which often refers pain to the left arm, face, or even mandibular teeth. Trigger points in both the masseter muscle and the temporalis muscle can refer pain to the teeth. It is very important for the dental practitioner to rule out myofascial pain as a source of a toothache to avoid any unnecessary, often irreversible, dental procedures. The neck is also a frequent source of pain referral to the face. Likewise, the temporal tendon is a common source of jaw pain and headache. Less common conditions that are sources for myofascial pain are mandibular dystonias and dyskinesias, which are more often found in elderly people and those taking antipsychotic medications. These conditions involve uncontrolled, repetitive, or sustained muscle contractions, which can be debilitating and are often quite painful. Two common types of disc derangements are disc displacement with and disc displacement without reduction. In both scenarios, the articular disc that normally sits between the condyle and the fossa/eminence becomes displaced (most often) anteriorly and is interfering with the smooth movement of the mandible. When the disc is displaced, its posterior band acts as a bump in the road. When a patient with a disc displacement with reduction opens his or her mouth, the condyle rotates, translates, pushes against, and then “jumps” underneath the posterior band of this disc. The disc is said to be “reduced” to its place on top of the condyle when the condyle pops back underneath the disc. This “reduction” often results in a popping or clicking sound. When that same patient closes his or her mouth, the disc slides back off the condyle close to the point of full mouth closure. This action can also be accompanied by a clicking or popping sound. In a patient with a disc displacement without reduction, the disc acts as a hurdle that can’t be overcome. Upon opening, the patient can rotate the condyle, but translation is limited when the condyle gets “stuck” behind the disc. As a result, the mouth opening is limited in this type of displacement, and the jaw often deflects to the affected side (imagine a road block on one side of the jaw, whereas the other side is free to move forward), and the patient will have difficulty moving the jaw laterally to the opposite side. Often, a disc displacement without reduction is painful, and the pain and limited mouth opening will prompt the patient to seek care. On the other hand, disc displacements with reduction are
usually not painful and the clicking sound is merely a nuisance to the patient (and sometimes his or her dining partners). It is important to note that a pain-free clicking jaw joint is a benign condition that may persist for decades and requires no treatment. An explanation of the condition and its prognosis should suffice. The discomfort from TMJDs will eventually dissipate overt time with simple self-care practices easing the symptoms (National Institute of Dental and Craniofacial Research, 2017). Cephalalgic pain (Headache) Headaches are common in the general population, and are a common accompaniment in patients with temporomandibular disorders (Paolo, et al., 2017). Headaches can be divided into two broad categories, primary and secondary. Primary headaches are idiopathic; they occur for no apparent underlying reason. Secondary headaches have a clear attributable cause (Rizzoli and Mullally , 2017). The most frequent type of primary headache is episodic tension-type headache, with an estimated 1-year prevalence of about 40% in the U.S. population (Rizzoli and Mulally, 2017). Because of the relative lack of epidemiologic data for tension-type headaches, the prevalence may be underestimated. A recent review showed that the prevalence of migraine headaches is about 12% of the U.S. population, with women being afflicted about three times more than men (Migraine Research Foundation, 2021). Migraines are debilitating headaches of moderate to severe intensity. They are usually unilateral and have a throbbing or pulsating quality. Migraines are often accompanied by nausea and sensitivity to light or noises and increase with physical activity. Because of these accompanying symptoms, patients will tell you they have to lie down in a dark room when they get a migraine headache. Migraines are typically divided into the categories of migraines with or without aura. About 25% of migraine sufferers experience an aura. An aura starts before the headache and can last between 5 to 60 minutes. It can consist of visual disturbances such as tunnel vision, blurry vision, flashing lights, and/or neurological signs such as numbness, dizziness, confusion, or hypersensitivity. Migraines are also divided into episodic (fewer than 15 headache days per month) or chronic (15 or more headache days per month). The presence of the following three features is considered a useful and reliable screener for diagnosing migraines: nausea, sensitivity to light, and disability. Tension-type headaches are usually bilateral and characterized by a pressing, tightening, nonpulsatile pain of mild to moderate intensity. Like migraines, they can be divided into episodic and chronic headaches. The episodic tension-type headache can be accompanied by sensitivity either to light or to noises, but not both, and not by nausea, whereas the chronic tension-type headache may be accompanied by mild nausea and sensitivity to light or noises. A tension-type headache does not worsen with physical activity, and typically does not prevent patients from continuing their daily activities. Other primary headaches, such as the trigeminal autonomic cephalalgias – a group of severe, stabbing, unilateral headaches usually centered around or behind the eye, accompanied by autonomic symptoms such as tearing or redness of the eye, a runny nose, or nasal congestion – are rare. As previously stated, secondary headaches have a clear attributable cause. Secondary headaches include those: ● Resulting from head or neck trauma. ● Attributed to vascular disorders, such as an ischemic stroke or aneurysm. ● Attributed to giant cell arteritis (also called temporal arteritis ), inflammation of the arterial walls. ● Resulting from high or low levels of cerebrospinal fluid. ● Resulting from overuse of medications or other substances. The dental practitioner may encounter patients with a type of secondary headache called a cervicogenic headache . It is a common chronic headache with a prevalence of about 1%
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