What are the causes of nocturnal leg cramps?

Causes of Nocturnal Leg Cramps

Nocturnal leg cramps are primarily associated with vascular disease, lumbar canal stenosis, cirrhosis, chronic kidney disease requiring hemodialysis, pregnancy, and neurological disorders. 1, 2

Medical Conditions Associated with Nocturnal Leg Cramps

• Vascular conditions:

  • Peripheral vascular disease (34% of patients with nocturnal leg cramps vs 12% of controls) 3
  • Cardiovascular diseases (82% of patients with nocturnal leg cramps vs 64% of controls) 3

• Neurological conditions:

  • Peripheral neurological deficits (12% of patients with nocturnal leg cramps vs 0% of controls) 3
  • Neurological diseases in general (36% of patients with nocturnal leg cramps vs 18% of controls) 3
  • Lumbar canal stenosis 2

• Other medical conditions:

  • Cirrhosis 2
  • Chronic kidney disease requiring hemodialysis 2
  • Pregnancy 2

Medication-Related Causes

Several medications have been strongly associated with triggering or worsening nocturnal leg cramps:

• Intravenous iron sucrose 2
• Hormone therapies (conjugated estrogens, raloxifene) 2
• NSAIDs (particularly naproxen) 2
• Teriparatide 2
• Diuretics (particularly potassium-sparing diuretics) 4
• Long-acting beta-agonists 5, 4

Pathophysiological Mechanisms

The exact mechanism of nocturnal leg cramps remains unknown, but they are likely caused by:

• Muscle fatigue 2
• Nerve dysfunction 2
• Not primarily due to electrolyte abnormalities as previously thought 2

Distinguishing Features

Nocturnal leg cramps must be differentiated from other conditions with similar presentations:

• Restless legs syndrome - characterized by an urge to move the legs rather than painful muscle contractions 1
• Claudication - pain triggered by activity and relieved by rest 2
• Myositis - generalized muscle inflammation and weakness 2
• Peripheral neuropathy - persistent sensory symptoms 2
• Periodic limb movements of sleep (PLMS) - repetitive limb movements during sleep that aren't painful 1

Clinical Pearls and Pitfalls

• Patients with nocturnal leg cramps typically have a higher number of medical problems than those without cramps 3
• The most common location for nocturnal leg cramps is the calf muscles 2
• Up to 60% of adults report experiencing nocturnal leg cramps 2
• Nocturnal leg cramps can cause severe insomnia, significantly impacting quality of life 2, 5
• Plantar flexion of the feet may elicit most sleep-related leg cramps 4

Diagnostic Approach

A thorough history and physical examination are usually sufficient to diagnose nocturnal leg cramps and differentiate them from other conditions. Laboratory evaluation and specialized testing are generally unnecessary unless an underlying condition is suspected 2.

When evaluating a patient with suspected nocturnal leg cramps, focus on:

1. Medication review (particularly diuretics, beta-agonists, NSAIDs, and hormone therapies)
2. Assessment for vascular disease
3. Neurological examination
4. Evaluation for other associated conditions (cirrhosis, kidney disease, pregnancy)