To develop a list of possible causes of muscular cramps, think of anatomy and physiology. Anatomically a muscle bundle is supplied by arteries, veins, and nerves. Considering the arteries will prompt the recall of arteriosclerosis, emboli, Leriche syndrome, and other conditions that interfere with the blood supply to the muscles. This is manifested by the familiar intermittent claudication. Considering the veins will call to mind varicose veins as a frequent cause of muscle cramps. Turning our attention to the nerve supply will help recall the various neurologic conditions that are associated with muscle cramps. Multiple sclerosis, amyotrophic lateral sclerosis, spinal cord injury, and any upper motor neuron lesion may be the cause of muscular cramps. Finally, the muscle itself may be involved by myositis, traumatic hemorrhage (i.e., charley horse), and “professional” cramps from the overuse of certain muscle groups.
Next, applying physiology to the analysis of possible causes of muscular cramps, we should easily remember the various fluid and electrolyte disorders that may be implicated. Hypocalcemia and hypomagnesemia due to hypoparathyroidism, rickets, malabsorption syndrome, chronic renal failure, and renal tubular acidosis are a prominent cause of muscular cramps. Hyponatremia from pathologic diaphoresis, diuretics, dilutional hyponatremia, inappropriate antidiuretic hormone (ADH) secretion, and chronic renal failure are also associated with muscle cramps. Finally, hypokalemia or alkalosis due to primary and secondary hyperaldosteronism, intestinal obstruction, milk–alkali syndrome, and hyperventilation may be the cause.
|
|
|
Muscular cramps |
A few additional disorders that may not be recalled by the above methods are lead poisoning, certain drugs, hysteria, fever, pregnancy, and strychnine poisoning.
|
|
|
Muscular cramps |
Approach to the Diagnosis
Clinically, one should look for absent or diminished pulses in the extremity involved, Chvostek and Trousseau signs of tetany, and neurologic signs of an upper motor neuron lesion. An occupational history may disclose that the patient is a miner or iron-worker or is exposed to excessive heat on the job. Occupations such as painters, writers, seamstresses, and compositors suggest the so-called professional cramps. Adson signs are positive in thoracic outlet syndrome. Cramps in the legs produced by walking a certain distance suggest peripheral arteriosclerosis and Leriche syndrome. This is also a sign of spinal stenosis. The initial laboratory workup involves a CBC, urinalysis, chemistry panel, and electrolytes. If a vascular cause is suspected, ultrasonography and perhaps venography or angiography may be indicated.
Other Useful Tests
1. Parathyroid hormone (PTH) assay (hypoparathyroidism)
2. 24-hour urine calcium level (hypoparathyroidism)
3. Plasma renin level (aldosteronism)
4. Urine aldosterone level (primary aldosteronism)
5. Endocrinology consult
6. Neurology consult
Case Presentation #67
A 67-year-old white man complained of cramps in both legs on walking one block. He also suffered chronic low back pain for the past year.
Question #1. Utilizing your knowledge of anatomy and physiology, what is your differential diagnosis?
Further history reveals that he is on medication for hypertension. Physical examination reveals good pulses in all four extremities. Neurologic examination aside from limited range of motion of his lumbar spine is unremarkable.
Question #2. What is your diagnosis now?
