Muscle weakness
Muscle weakness: Excerpt from Handbook of Signs & Symptoms (Third Edition)
Muscle weakness is detected by observing and measuring the strength of an individual muscle or muscle group. It can result from a malfunction in the cerebral hemispheres, brain stem, spinal cord, nerve roots, peripheral nerves, or myoneural junctions and within the muscle itself. Muscle weakness occurs with certain neurologic, musculoskeletal, metabolic, endocrine, and cardiovascular disorders; as a response to certain drugs; and after prolonged immobilization.
History and physical examination
Begin by determining the location of the patient’s muscle weakness. Ask if he has difficulty with specific movements such as rising from a chair. Find out when he first noticed the weakness; ask him whether it worsens with exercise or as the day progresses. Also ask about related symptoms, especially muscle or joint pain, altered sensory function, and fatigue.
Obtain a medical history, noting especially chronic disease, such as hyperthyroidism; musculoskeletal or neurologic problems, including recent trauma; a family history of chronic muscle weakness, especially in males; and alcohol and drug use.
Focus your physical examination on evaluating muscle strength. Test all major muscles bilaterally. (See Testing muscle strength, pages 418 and 419.) When testing, make sure that the patient’s effort is constant; if it isn’t, suspect pain or other reluctance to make the effort. If the patient complains of pain, ease or discontinue testing and have him try the movements again. Remember that the patient’s dominant arm, hand, and leg are somewhat stronger than their nondominant counterparts. Besides testing individual muscle strength, test for range of motion (ROM) at all major joints (shoulder, elbow, wrist, hip, knee, and ankle). Also test sensory function in the involved areas, and test deep tendon reflexes (DTRs) bilaterally.
Medical causes
Amyotrophic lateral sclerosis (ALS)
ALS typically begins with muscle weakness and atrophy in one hand that rapidly spread to the arm and then to the other hand and arm. Eventually, these effects spread to the trunk, neck, tongue, larynx, pharynx, and legs; progressive respiratory muscle weakness leads to respiratory insufficiency.
Anemia
Varying degrees of muscle weakness and fatigue are exacerbated by exertion and temporarily relieved by rest. Other signs and symptoms include pallor, tachycardia, paresthesia, and bleeding tendencies.
Brain tumor
Signs and symptoms of muscle weakness vary with the location and size of the tumor. Associated findings include a headache, vomiting, diplopia, decreased visual acuity, a decreased level of consciousness (LOC), pupillary changes, decreased motor strength, hemiparesis, hemiplegia, diminished sensations, ataxia, seizures, and behavioral changes.
Guillain-Barré syndrome
Rapidly progressive, symmetrical weakness and pain ascends from the feet to the arms and facial nerves and may progress to total motor paralysis and respiratory failure. Associated findings include sensory loss or paresthesia, muscle flaccidity, loss of DTRs, tachycardia or bradycardia, fluctuating hypertension and orthostatic hypotension, diaphoresis, bowel and bladder incontinence, facial diplegia, dysphagia, dysarthria, and hypernasality.
Herniated disk
Pressure on nerve roots leads to muscle weakness, disuse and, ultimately, atrophy. The primary symptom is severe low back pain, possibly radiating to the buttocks, legs, and feet — usually on one side. Diminished reflexes and sensory changes may also occur.
Hypercortisolism
Hypercortisolism may cause limb weakness and eventually atrophy. Related cushingoid features include buffalo hump, moon face, truncal obesity, purple striae, thin skin, acne, elevated blood pressure, fatigue, hyperpigmentation, easy bruising, poor wound healing, and diaphoresis. The male patient may be impotent; the female patient may exhibit hirsutism and menstrual irregularities.
Myasthenia gravis
Gradually progressive skeletal muscle weakness and fatigue are the cardinal symptoms of myasthenia gravis. Typically, weakness is mild upon awakening, but worsens during the day. Early signs include weak eye closure, ptosis, and diplopia; blank, masklike facies; difficulty chewing and swallowing; nasal regurgitation of fluid with hypernasality; and a hanging jaw and bobbing head. Respiratory muscle involvement may eventually lead to respiratory failure.
Osteoarthritis
Osteoarthritis is a chronic disorder that causes progressive muscle disuse and weakness that lead to atrophy.
Parkinson’s disease
Muscle weakness accompanies rigidity in Parkinson’s disease, a degenerative disorder. Related findings include a unilateral pill-rolling tremor, a propulsive gait, dysarthria, bradykinesia, drooling, dysphagia, masklike facies, and a high-pitched, monotone voice.
Peripheral nerve trauma
Prolonged pressure on or injury to a peripheral nerve causes muscle weakness and atrophy. Other findings include paresthesia or sensory loss, pain, and loss of reflexes supplied by the damaged nerve.
Potassium imbalance
With hypokalemia, temporary generalized muscle weakness may be accompanied by nausea, vomiting, diarrhea, decreased mentation, leg cramps, diminished reflexes, malaise, polyuria, dizziness, hypotension, and arrhythmias.
With hyperkalemia, weakness may progress to flaccid paralysis accompanied by irritability and confusion, hyperreflexia, paresthesia or anesthesia, oliguria, anorexia, nausea, diarrhea, abdominal cramps, tachycardia or bradycardia, and arrhythmias.
Rhabdomyolysis
Signs and symptoms include muscle weakness or pain, a fever, nausea, vomiting, malaise, and dark urine. Acute renal failure, due to renal structure obstruction and injury from the kidneys’attempt to filter myoglobin from the bloodstream, is a common complication.
Rheumatoid arthritis
With rheumatoid arthritis, symmetrical muscle weakness may accompany increased warmth, swelling, and tenderness in involved joints; pain; and stiffness, restricting motion.
Seizure disorder
Temporary generalized muscle weakness may occur after a generalized tonic-clonic seizure; other postictal findings include a headache, muscle soreness, and profound fatigue.
Spinal trauma and disease
Trauma can cause severe muscle weakness, leading to flaccidity or spasticity and, eventually, paralysis. Infection, tumor, and cervical spondylosis or stenosis can also cause muscle weakness.
Stroke
Depending on the site and extent of damage, a stroke may produce contralateral or bilateral weakness of the arms, legs, face, and tongue, possibly progressing to hemiplegia and atrophy. Associated effects include dysarthria, aphasia, ataxia, apraxia, agnosia, ipsilateral paresthesia or sensory loss, vision disturbances, an altered LOC, amnesia and poor judgment, personality changes, bowel and bladder dysfunction, a headache, vomiting, and seizures.
Other causes
Drugs
Generalized muscle weakness can result from prolonged corticosteroid use, digoxin, and excessive doses of dantrolene. Aminoglycoside antibiotics may worsen weakness in patients with myasthenia gravis.
Immobility
Immobilization in a cast, a splint, or traction can lead to muscle weakness in the involved extremity; prolonged bed rest or inactivity results in generalized muscle weakness.
Special considerations
Provide assistive devices as necessary, and protect the patient from injury. If he has concomitant sensory loss, guard against pressure ulcer formation and thermal injury. With chronic weakness, provide ROM exercises or splint limbs as necessary. Arrange therapy sessions to allow for adequate rest periods, and administer pain medications as needed.
Prepare the patient for blood tests, muscle biopsy, electromyography, nerve conduction studies, and X-rays or computed tomography scans.
Pediatric pointers
Muscular dystrophy, usually the Duchenne type, is a major cause of muscle weakness in children.
Pictures
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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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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