Cramp

A cramp is a sudden, involuntary, painful skeletal muscle contraction or overshortening associated with electrical activity. While generally temporary and non-damaging, cramps can cause significant pain and a paralysis-like immobility of the affected muscle.

They often occur at rest, usually at night (nocturnal leg cramps), and are common in pregnancy, physical exercise, age, or idiopathic conditions where no underlying pathology is present.

Cramps differ from muscle spasms in that they are sustained and painful. They can also be distinguished from muscle contracture and dystonia through their sudden onset, acute pain, single muscle involvement, and resolution post-stretching.

Restless leg syndrome is not synonymous with muscle cramps.

Causes

Skeletal muscle cramps may result from muscle fatigue or a lack of electrolytes such as sodium, potassium, or magnesium. Certain medical conditions and treatments can also induce cramps. Common causes include:

• Hyperflexion
• Hypoxia
• Temperature changes
• Dehydration
• Low blood salt levels

Medical conditions associated with cramps include pregnancy, kidney disease, thyroid disease, varicose veins, multiple sclerosis, cardiovascular disease, hemodialysis, and lumbar canal stenosis. As early as 1965, research suggested that excess insulin (hyperinsulinaemia) could result in leg cramps and restless legs syndrome.

Skeletal Muscle Cramps

Skeletal muscles, which are typically voluntarily controlled, can cramp from strenuous physical activity or even while at rest. Commonly affected muscles include the calves, thighs, and arches of the foot. These cramps can be extremely painful, sometimes immobilising the affected limb and causing muscle pain that can last up to a week, depending on the individual's fitness level and age.

Nocturnal Leg Cramps

Nocturnal leg cramps occur at night or during rest, affecting muscles in the calves, soles of the feet, or other areas. These cramps are more common in older adults and can cause distress and anxiety due to their painful nature. The precise cause is unclear, but potential contributors include dehydration, low levels of minerals, and reduced blood flow from prolonged sitting or lying down. Nocturnal leg cramps are often considered normal during late pregnancy.

Symptoms

Cramps manifest as sudden muscle pain and a paralysis-like immobility. Nocturnal leg cramps can last from a few seconds to several minutes, with residual muscle soreness.

Diagnosis

Differential diagnoses for leg cramps include restless legs syndrome, claudication, myositis, and peripheral neuropathy. These can be differentiated through careful history and physical examination.

Treatment

Treatment of simple muscle cramps includes stretching, massage, and maintaining adequate hydration. Specific medications and treatments for cramps include:

• Quinine: Previously used but no longer recommended due to potential severe side effects.
• Magnesium: Commonly used but with limited effectiveness in older adults and unknown efficacy in pregnancy-related cramps.
• Electrolyte Replenishment: Appropriate fluids and potassium for exertional heat cramps.
• Other Medications: Vitamin B complex, naftidrofuryl, lidocaine, and calcium channel blockers may also be effective.

Cramps Caused by Treatments

Various medications can induce nocturnal leg cramps, including diuretics, intravenous iron sucrose, conjugated estrogens, teriparatide, naproxen, raloxifene, long-acting adrenergic beta-agonists, and statins. Statins, in particular, are associated with significant adverse muscular effects in up to 80% of athletes and 10-25% of the general population on statins. Coenzyme Q10 supplementation may help to mitigate some statin-related side effects.

Prevention

Preventative measures for muscle cramps include adequate conditioning, stretching, mental preparation, hydration, and electrolyte balance.

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Self-assessment MCQs (single best answer)

What is a cramp?

Which of the following is NOT a common cause of skeletal muscle cramps?

Which condition is typically NOT associated with nocturnal leg cramps?

Which of these treatments is no longer recommended for muscle cramps due to severe side effects?

Which muscle is commonly affected by nocturnal leg cramps?

What is the difference between cramps and muscle spasms?

Which mineral is NOT typically associated with the prevention or treatment of muscle cramps?

What is a key distinguishing feature of cramps compared to muscle contracture and dystonia?

Which medication is associated with significant adverse muscular effects in patients, particularly athletes?

Which of the following is NOT a recommended preventative measure for muscle cramps?