Muscle atrophy [Muscle wasting]
Muscle atrophy [Muscle wasting]: Excerpt from Handbook of Signs & Symptoms (Third Edition)
Muscle atrophy results from denervation or prolonged muscle disuse. When deprived of regular exercise, muscle fibers lose bulk and length, producing a visible loss of muscle size and contour and apparent emaciation or deformity in the affected area. Even slight atrophy usually causes some loss of motion or power.
Atrophy usually results from neuromuscular disease or injury. However, it may also stem from certain metabolic and endocrine disorders and prolonged immobility. Some muscle atrophy also occurs with aging.
History and physical examination
Ask the patient when and where he first noticed the muscle wasting and how it has progressed. Also ask about associated signs and symptoms, such as weakness, pain, loss of sensation, and recent weight loss. Review the patient’s medical history for chronic illnesses; musculoskeletal or neurologic disorders, including trauma; and endocrine and metabolic disorders. Ask about his use of alcohol and drugs, particularly steroids.
Begin the physical examination by determining the location and extent of atrophy. Visually evaluate small and large muscles. Check all major muscle groups for size, tonicity, and strength. (See Testing muscle strength, pages 418 and 419.) Measure the circumference of all limbs, comparing sides. (See Measuring limb circumference.) Check for muscle contractures in all limbs by fully extending joints and noting pain or resistance. Complete the examination by palpating peripheral pulses for quality and rate, assessing sensory function in and around the atrophied area, and testing deep tendon reflexes (DTRs).
Medical causes
Amyotrophic lateral sclerosis (ALS)
Initial symptoms of ALS include muscle weakness and atrophy that typically begin in one hand, spread to the arm, and then develop in the other hand and arm. Eventually, weakness and atrophy spread to the trunk, neck, tongue, larynx, pharynx, and legs; progressive respiratory muscle weakness leads to respiratory insufficiency. Other findings include muscle flaccidity, fasciculations, hyperactive DTRs, slight leg muscle spasticity, dysphagia, impaired speech, excessive drooling, and depression.
Burns
Fibrous scar tissue formation, pain, and loss of serum proteins from severe burns can limit muscle movement, resulting in atrophy.
Hypothyroidism
Reversible weakness and atrophy of proximal limb muscles may occur in hypothyroidism. Associated findings commonly include muscle cramps and stiffness; cold intolerance; weight gain despite anorexia; mental dullness; dry, pale, cool, doughy skin; puffy face, hands, and feet; and bradycardia.
Meniscal tear
Quadriceps muscle atrophy, resulting from prolonged knee immobility and muscle weakness, is a classic sign of meniscal tear, a traumatic disorder.
Multiple sclerosis
Multiple sclerosis is a degenerative disease that may produce arm and leg atrophy as a result of chronic progressive weakness; spasticity and contractures may also develop. Associated signs and symptoms typically wax and wane and include diplopia and blurred vision, nystagmus, hyperactive DTRs, sensory loss or paresthesia, dysarthria, dysphagia, incoordination, an ataxic gait, intention tremors, emotional lability, impotence, and urinary dysfunction.
Osteoarthritis
Osteoarthritis is a chronic disorder that eventually causes atrophy proximal to involved joints as a result of progressive weakness and disuse. Other late signs and symptoms include bony joint deformities, such as Heberden’s nodes on the distal interphalangeal joints, Bouchard’s nodes on the proximal interphalangeal joints, crepitus and fluid accumulation, and contractures.
Parkinson’s disease
With Parkinson’s disease, muscle rigidity, weakness, and disuse may produce muscle atrophy. The patient may exhibit insidious resting tremors that usually begin in the fingers (pill-rolling tremor), worsen with stress, and ease with purposeful movement and sleep. He may also develop bradykinesia; a characteristic propulsive gait; a high-pitched, monotone voice; masklike facies; drooling; dysphagia; dysarthria; and, occasionally, oculogyric crisis or blepharospasm.
Peripheral neuropathy
With peripheral neuropathy, muscle weakness progresses slowly to flaccid paralysis and eventually atrophy. Distal extremity muscles are generally affected first. Associated findings include a loss of vibration sense; paresthesia, hyperesthesia, or anesthesia in the hands and feet; mild to sharp, burning pain; anhidrosis; glossy red skin; and diminished or absent DTRs.
Protein deficiency
If chronic, protein deficiency may lead to muscle weakness and atrophy. Other findings include chronic fatigue, apathy, anorexia, dry skin, peripheral edema, and dull, sparse, dry hair.
Rheumatoid arthritis
Muscle atrophy occurs in the late stages of rheumatoid arthritis as joint pain and stiffness decrease range of motion (ROM) and discourage muscle use.
Spinal cord injury
Trauma to the spinal cord can produce severe muscle weakness and flaccid, then spastic, paralysis, eventually leading to atrophy. Other signs and symptoms depend on the level of injury, but may include respiratory insufficiency or paralysis, sensory losses, bowel and bladder dysfunction, hyperactive DTRs, a positive Babinski’s reflex, sexual dysfunction, priapism, hypotension, and anhidrosis (usually unilateral).
Other causes
Drugs
Prolonged steroid therapy interferes with muscle metabolism and leads to atrophy, most prominently in the limbs.
Immobility
Prolonged immobilization from bed rest, casts, splints, or traction may cause muscle weakness and atrophy.
Special considerations
Because contractures can occur as atrophied muscle fibers shorten, help the patient maintain muscle length by encouraging him to perform frequent, active ROM exercises. If he can’t actively move a joint, provide active assistive or passive exercises, and apply splints or braces to maintain muscle length. If you find resistance to full extension during exercise, use heat, pain medication, or relaxation techniques to relax the muscle. Then slowly stretch it to full extension. (Caution: Don’t pull or strain the muscle; you may tear muscle fibers and cause further contracture.) If these techniques fail to correct the contracture, use moist heat, a whirlpool bath, resistive exercises, or ultrasound therapy. If these techniques aren’t effective, surgical release of contractures may be necessary.
Teach the patient to use necessary assistive devices properly to ensure his safety and prevent falls. Have the patient consult a physical therapist for a specialized therapy regimen.
Prepare the patient for electromyography, nerve conduction studies, muscle biopsy, and X-rays or computed tomography scans.
Pediatric pointers
In young children, profound muscle weakness and atrophy can result from muscular dystrophy. Muscle atrophy may also result from cerebral palsy and poliomyelitis and from paralysis associated with meningocele and myelomeningocele.
Pictures
![Muscle atrophy [Muscle wasting] - 2824.1.jpg](/bookimages/5/2824.1.jpg)
Book Source Details
- Book Title: Handbook of Signs & Symptoms (Third Edition)
- Author(s): Springhouse
- Year of Publication: 2006
- Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2006 Lippincott Williams & Wilkins.
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