Cramp

Cramps are unpleasant, often painful sensations caused by muscle contraction or overshortening. The common causes of skeletal muscle cramps are muscle fatigue and a sodium imbalance. Smooth muscle cramps may be due to menstruation or Gastroenteritis.

Differential diagnosis

Causes of cramping include hyperflexion, hypoxia, exposure to large changes in temperature, dehydration, or low blood salt. Muscle cramps may also be a symptom or complication of pregnancy, kidney disease, thyroid disease, hypokalemia, or hypocalcemia (as conditions), restless-leg syndrome, varicose veins, and multiple sclerosis.


Electrolyte disturbance may cause cramping and muscle tetany, particularly hypokalaemia and hypocalcaemia. This disturbance arises as the body loses large amounts of interstitial fluid through sweat. This interstitial fluid comprises mostly water and table salt (sodium chloride). The loss of osmotically active particles outside of muscle cells leads to a disturbance of the osmotic balance and swelling of muscle cells, as these contain more osmotically active particles. This causes the calcium pump between the muscle lumen and sarcoplasmic reticulum to short circuit; the calcium ions remain bound to the troponin, continuing muscle contraction. This may occur when lactic acid is high in the cells.
As early as 1965, researchers observed that leg cramps and restless-leg syndrome result from excess insulin, sometimes called hyperinsulinemia. Hypoglycemia & reactive hypoglycemia are associated with excess insulin [or insufficient glucagon], and avoidance of low blood glucose concentration may help to avoid cramps.

Smooth muscle cramps

Smooth muscle contractions lie at the heart of the cramping (or colicky) pain of internal organs. These include the intestine, uterus, ureter (in kidney stone pain), and various others.

Menstrual cramps

Menstruation is also likely to cause abdominal cramps of varying severity that may radiate to the lower back and thighs. Menstrual cramps can be treated with ibuprofen, acetaminophen (paracetamol), stretching exercises, or the application of heat through means such as warm baths or heating pads. Menstrual cramps that do not respond to self treatment may be symptomatic of endometriosis or other health problems.

Skeletal muscle cramps

Skeletal muscles can be voluntarily controlled. Among skeletal muscles, those which cramp the most often are the calves, thighs, and arches of the foot. These cramps are seemingly associated with strenuous activity and can be intensely painful.

Nocturnal leg cramps

Nocturnal leg cramps are involuntary muscle contractions that occur in the calves, soles of the feet, or other muscles in the body during the night or (less commonly) while resting. Only a few fibers of a muscle may be activated. The duration of nocturnal leg cramps is variable with cramps lasting anywhere from a few seconds to several minutes. Muscle soreness may remain after the cramp itself ends. These cramps are erroneously believed to be more common in older people. They happen quite frequently in teenagers and in some people while exercising at night. Usually, putting some pressure on the affected leg by walking some distance will end the cramp.

The precise cause of these cramps is unclear. Potential contributing factors include dehydration, low levels of certain minerals (magnesium, potassium, calcium, and sodium), and reduced blood flow through muscles attendant in prolonged sitting or lying down. Less common causes include more serious conditions or drug use.

Nocturnal leg cramps may sometimes be relieved by stretching the affected leg and pointing the toes upward. Quickly standing up and walking a few steps may also shorten the duration of a cramp.

Nocturnal leg cramps (almost exclusively calf cramps) are considered to be 'normal' during the late stages of pregnancy. They can, however, vary in intensity from mild to incredibly painful.

Iatrogenic causes

Statins cause myalgia and cramps among other possible side effects, including substantially lowering blood glucose concentration.Additional factors, which increase the probability for these side effects, are physical exercise, age, female gender, history of cramps, and hypothyroidism. Up to 80% of athletes using statins suffer significant adverse muscular effects, including cramps;[8] the rate appears to be approximately 10-25% in a typical statin-using population.In some cases, adverse effects disappear after switching to a different statin; however, they should not be ignored if they persist, as they can, in rare cases, develop into more serious problems. Coenzyme Q10 supplementation can be helpful to avoid some statin-related adverse effects, but currently there is not enough evidence to prove the effectiveness in avoiding myopathy or myalgia.

Pathophysiology


Skeletal muscles work as antagonistic pairs. Contracting one skeletal muscle requires the relaxation of the opposing muscle in the pair. Cramps can occur when muscles are unable to relax properly due to myosin fibers not fully detaching from actin filaments. In skeletal muscle, both ATP (energy) and magnesium must attach to the myosin fibers in order for them to disassociate from the muscle and allow relaxation — the absence of either of these in sufficient quantities means that the myosin remains attached to actin. An attempt to force a muscle cramped in this way to extend (by contracting the opposing muscle) can tear muscle tissue and worsen the pain. The muscle must be allowed to recover (take in Mg and resynthesize ATP), before the myosin fibres can detach and allow the muscle to relax.

Treatment
Conservative

Muscle cramps due to fatigue can be treated by stretching and massage.With exertional heat cramps due to electrolyte abnormalities (primarily sodium loss and not calcium, magnesium, and potassium ) appropriate fluids and sufficient salt improves symptoms.

Medication

Vitamin B complex, naftidrofuryl, and calcium channel blockers may be effective for muscle cramps. Quinine is likely effective for this indication however due to side effects its use should only be considered if other treatments have failed and in light of these concerns.