What is the initial workup for a patient presenting with cramps?

Initial Workup for Muscle Cramps

The initial workup for a patient presenting with muscle cramps should include assessment of electrolyte abnormalities (particularly hypokalemia and hypomagnesemia), medication review, and evaluation for underlying medical conditions such as liver disease, thyroid dysfunction, and peripheral neuropathy.

Definition and Classification

Muscle cramps are painful, sudden, involuntary muscle contractions that are generally self-limiting. They can be categorized as:

• Exercise-associated muscle cramps
• Disease-related cramps
• Medication-induced cramps
• Idiopathic cramps (including nocturnal leg cramps)

Initial Laboratory Evaluation

The following tests should be performed in the initial workup:

• Complete blood count (CBC) with differential to evaluate for anemia and other hematologic abnormalities 1
• Comprehensive metabolic panel to assess:
  • Electrolytes (sodium, potassium, calcium)
  • Renal function (BUN, creatinine)
  • Hepatic function (liver enzymes) 1
• Thyroid-stimulating hormone (TSH) to detect thyroid dysfunction 1
• Magnesium level (often low in patients with muscle cramps)
• Fasting blood glucose to evaluate for diabetes 1

Medication Review

Conduct a thorough medication review, focusing on medications strongly associated with muscle cramps:

• Intravenous iron sucrose
• Conjugated estrogens
• Raloxifene
• Naproxen
• Teriparatide
• Diuretics (which can cause electrolyte imbalances)

History and Physical Examination Elements

Key History Elements

• Timing of cramps (nocturnal vs. daytime)
• Relationship to exercise
• Frequency and severity
• Location (calf muscles are most common)
• Associated symptoms
• Impact on sleep and quality of life

Physical Examination

• Neurological examination to assess for peripheral neuropathy
• Vascular examination (pulses, capillary refill)
• Musculoskeletal examination for signs of myopathy
• Assessment for signs of liver disease (in patients with cirrhosis) 2

Differential Diagnosis

Differentiate muscle cramps from:

• Restless legs syndrome
• Claudication
• Myositis
• Peripheral neuropathy
• Dystonia
• Tetany

Special Considerations

Liver Disease

In patients with liver disease, muscle cramps are common and may respond to albumin (20-40 g/week) 2

Exercise-Associated Cramps

For patients with exercise-associated cramps, evaluate hydration status and electrolyte balance, though recent research suggests that dehydration alone may not be the primary cause 3

Treatment Approaches

Based on the underlying cause identified in the workup:

1. Electrolyte correction if abnormalities are found
2. Medication adjustment if drug-induced
3. Baclofen (10 mg/day, with weekly increases up to 30 mg/day) for persistent cramps, especially in liver disease 2
4. Physical therapy with stretching exercises
5. Magnesium supplementation for deficiency or empirically

Common Pitfalls to Avoid

• Attributing all cramps to electrolyte abnormalities without complete evaluation
• Overlooking medication side effects as potential causes
• Failing to consider underlying medical conditions (liver disease, thyroid disorders)
• Using quinine sulfate, which is no longer recommended due to safety concerns 4

Remember that while laboratory evaluation is important, in many cases of nocturnal leg cramps, a history and physical examination are usually sufficient to make the diagnosis, and specialized testing is often unnecessary 4.