In medicine, a spasm is a sudden, involuntary contraction of a muscle, a group of muscles, or a hollow organ such as a heart, or a similarly sudden contraction of an orifice. It most commonly refers to a muscle cramp which is often accompanied by a sudden burst of pain, but is usually harmless and ceases after a few minutes. There is a variety of other causes of involuntary muscle contractions, which may be more serious, depending on the cause.
The word "spasm" may also refer to a temporary burst of energy, activity, emotion, Eustress, stress, or anxiety unrelated to, or as a consequence of, involuntary muscle activity.
Temporomandibular joint dysfunction (sometimes abbreviated to TMD or TMJD and also termed temporomandibular joint dysfunction syndrome, temporomandibular disorder or many other names), is an umbrella term covering pain and dysfunction of the muscles of mastication (the muscles that move the jaw) and the temporomandibular joints (the joints which connect the mandible to the skull). The most important feature is pain, followed by restricted mandibular movement, and noises from the temporomandibular joints (TMJ) during jaw movement. Although TMD is not life threatening, it can detriment quality of life, because the symptoms can become chronic and difficult to manage. TMD is thought to be very common. About 20-30% of the adult population are affected to some degree. Usually people affected by TMD are between 20 and 40 years of age, and it is more common in females than males. TMD is the second most frequent cause of orofacial pain after dental pain (e.g. toothache).
TMD is a symptom complex rather than a single condition, and it is thought to be caused by multiple factors. However, these factors are poorly understood, and there is disagreement as to the relative importance of these factors with each other. There are many treatments available, although there is a general lack of evidence for any treatment in TMD, and no widely accepted treatment protocol exists. Common treatments that are used include provision of occlusal splints, psychosocial interventions like cognitive behavioural therapy, and medications like analgesics (pain killers) or others. Most sources now agree that no irreversible treatment should be carried out for TMD.
The temporomandibular joint is the joint of the jaw and is frequently referred to as TMJ. There are two TMJs, one on each side, working in unison. The name of the joint is derived from the two bones which form the joint: the upper temporal bone which is part of the cranium (skull), and the lower jawbone or mandible.
Formation of the TMJ occurs at around 12 weeks in utero when the joint spaces and the articular disc develop. At approximately 10 weeks the component of the fetus future joint becomes evident in the mesenchyme between condylar cartilage of the mandible and the developing temporal bone. Two slits like joint cavities and intervening disk make their appearance in this region by 12 weeks. The mesenchyme around the joint begins to form the fibrous joint capsule. Very little is known about the significance of newly forming muscles in joint formation. The developing superior head of the lateral pterygoid muscle attaches to the anterior portion of the fetal disk. The disk also continues posterior through the petrotympanic fissure and attaches to the malleus of middle ear.
A muscle relaxant is a drug which affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate symptoms such as muscle spasms, pain, and hyperreflexia. The term "muscle relaxant" is used to refer to two major therapeutic groups: neuromuscular blockers and spasmolytics. Neuromuscular blockers act by interfering with transmission at the neuromuscular end plate and have no central nervous system (CNS) activity. They are often used during surgical procedures and in intensive care and emergency medicine to cause temporary paralysis. Spasmolytics, also known as "centrally acting" muscle relaxants, are used to alleviate musculoskeletal pain and spasms and to reduce spasticity in a variety of neurological conditions. While both neuromuscular blockers and spasmolytics are often grouped together as muscle relaxants, the term is commonly used to refer to spasmolytics only.
The earliest known use of muscle relaxant drugs dates back to the 16th century, when European explorers encountered natives of the Amazon Basin in South America using poison-tipped arrows that produced death by skeletal muscle paralysis. This poison, known today as curare, led to some of the earliest scientific studies in pharmacology. Its active ingredient, tubocurarine, as well as many synthetic derivatives, played a significant role in scientific experiments to determine the function of acetylcholine in neuromuscular transmission. By 1943, neuromuscular blocking drugs became established as muscle relaxants in the practice of anesthesia and surgery.