Muscle Cramps
Muscle Cramps: Excerpt from Field Guide to Bedside Diagnosis
Differential Overview
❑ Ordinary muscle cramp
❑ Overuse
❑ Dehydration
❑ Drugs/toxins
❑ Hypokalemia
❑ Hyponatremia
❑ Hyperventilation
❑ Vascular insufficiency
❑ Restless legs syndrome
❑ Hypocalcemia
❑ Dystonia
❑ Amyotrophic lateral sclerosis
❑ Hemifacial spasms
❑ Spinal cord lesion
❑ Muscle enzyme deficiency
❑ Myotonic dystrophy
❑ Black widow spider bite
❑ Tetanus
Diagnostic Approach
Nocturnal leg cramps are common and easily recognized. They are due to muscle overuse, structural conditions such as flat feet, prolonged sitting, standing on hard floors, extracellular volume depletion, or electrolyte imbalance.
Generalized cramps suggest chronic disease of the motor neuron such as amyotrophic lateral sclerosis. Cramps recurrent and localized to one muscle group suggest nerve root disease. Myotonia is difficulty releasing a grip (handshake or doorknob) that improves with repeated contractions.
Clinical Findings
Ordinary muscle cramp Cramping presents as a painful involuntary cramp of a single muscle with a palpable knot. It is most often nocturnal appearing in the legs (calf and ventral foot), accompanied by local fasciculations and relieved by stretching.
Overuse A painful cramp occurs during exercise/use. As a result of inappropriate contractions of opposing muscle groups, unusual postures often result. Swimmer’s cramp is a striking example of this. “Professional cramps” also occur with the overuse of muscle groups, e.g., writer’s cramp or lip and facial muscle cramping in horn players.
Dehydration It appears with excessive sweating and loss of salt as in vigorous exertion or fever. A similar phenomenon occurs during dialysis, probably because of hyposmolarity.
Drugs/toxins Statins can produce muscle toxicity ranging from muscle aching, pain, and cramps to severe muscle inflammation. Strychnine poisoning can cause spasms that are clonic rather than tetanic and that affect the whole body rather than primarily the extremities. Ergot excess causes muscle pains and intermittent claudication.
Hypokalemia These cramps appear like ordinary muscle cramps and occur in the setting of diuretic use.
Hyponatremia Sodium loss is most often caused by diuretics or SIADH.
Hyperventilation Painless carpal-pedal spasms appear along with tingling around the mouth, and in the hands and feet. The patient often does not recognize that their breathing has become rapid and deep.
Vascular insufficiency Intermittent claudication, not a true cramp, is muscle pain predictably precipitated by exertion and relieved by rest.
Restless legs syndrome Nocturnal creeping, aching, or writhing sensations appear in the legs. Underlying causes include iron deficiency anemia, pregnancy, rheumatoid arthritis, and uremia.
Hypocalcemia Tetany, paroxysmal, or sustained contraction (hours to days) of the extremities and increased excitability of the nerves to mechanical stimulation, are found. Paresthesias and positive Chvostek and Trousseau signs will usually be present. An “accoucheur’s hand” may develop, with the distal fingers extended, metacarpophalangeal joints flexed, and the thumb drawn into the palm, either spontaneously or in response to blood pressure cuff compression of the arm (Chvostek sign).
Dystonia Sustained postures develop as a result of simultaneous contraction of antagonist and agonist muscles, occurring with antipsychotic or antidepressant medications.
Amyotrophic lateral sclerosis Weakness, atrophy, and fasciculations accompany the cramps.
Hemifacial spasms Any facial movement, such as blinking, leads to a fine twitching or prolonged facial spasm. It is caused by compression of the facial nerve in the posterior fossa.
Spinal cord lesion Symptoms include stiffness, muscle cramps, and flexor spasms of the thigh, knee, and foot set off by cutaneous or visceral stimuli. Autonomic signs such as sweating, piloerection, and incontinence are also present.
Muscle enzyme deficiency Phosphorylase/phosphofructokinase deficiency causes painful cramps evoked by vigorous exertion. Carnitine palmityl deficiency causes cramps to occur during prolonged exercise, especially when the patient is fasting, following a low carbohydrate diet, or spending time in a cold climate.
Myotonic dystrophy The hallmark is delayed relaxation of voluntary contraction.
Black widow spider bite Persistent muscle rigidity and painful cramps occur in persons who have been bitten.
Tetanus Involuntary spasm is superimposed on continuous stiffness. Trismus (“lock-jaw”) occurs early in the course, along with rigid hyperextension of the neck. There will usually be a cutaneous infected source.
Book Source Details
- Book Title: Field Guide to Bedside Diagnosis
- Author(s): David S. Smith
- Year of Publication: 2007
- Copyright Details: Field Guide to Bedside Diagnosis, 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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More About This Book:
Title: Field Guide to Bedside Diagnosis
Authors: David S. Smith
Publisher: Lippincott Williams & Wilkins
Copyright: 2007
ISBN: 0-78178-165-5
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