MUSCULAR CRAMPS
MUSCULAR CRAMPS: Excerpt from Differential Diagnosis in Primary Care
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.
A few additional disorders that may not be recalled by the above methods are
lead poisoning, certain drugs, hysteria, fever, pregnancy, and strychnine
poisoning.
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
-
Parathyroid hormone (PTH) assay (hypoparathyroidism)
- 24-hour urine calcium level (hypoparathyroidism)
- Plasma renin level (aldosteronism)
- Urine aldosterone level (primary aldosteronism)
- Endocrinology consult
- Neurology consult
Pictures
Book Source Details
- Book Title: Differential Diagnosis in Primary Care
- Author(s): R. Douglas Collins MD, FACP
- Year of Publication: 2007
- Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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