Alternate Names: Lack of strength; Muscle weakness

Considerations: Weakness is a very important symptom. The feeling of weakness may be subjective (the person feels weak but has no measurable loss of strength) or concrete (measurable loss of strength). Weakness may be generalized (total body weakness) or localized to a specific area, side of the body, limb, and so on.

A subjective feeling of weakness usually is generalized and associated with infectious diseases such as infectious mononucleosis and influenza.

Weakness is particularly important when it occurs in only one area of the body (localized or focal weakness). Localized weakness may follow a stroke, exacerbation of multiple sclerosis, or trauma to a motor nerve root or peripheral nerve.

Common Causes: Measurable weakness may result from a variety of conditions including metabolic, neurologic, primary muscular diseases, and toxic disorders.
METABOLIC

• diabetes
• Addison’s disease
• thyrotoxicosis

• stroke (often focal or localized weakness)
• multiple sclerosis (may be focal)
• amyotrophic lateral sclerosis (focal developing to generalized)
• cerebral palsy (focal weakness associated with spasticity)
• Guillain-Barre syndrome
• peroneal muscular atrophy
• Werdnig-Hoffmann disease (spinal muscular atrophy)

• muscular dystrophy (Duchenne)
• Becker muscular dystrophy
• myotonic dystrophy
• dermatomyositis

• organophosphate poisoning (insecticides, nerve gas)
• paralytic shellfish poisoning
• botulism

• myasthenia gravis (an autoimmune disorder that interferes with the transmission of nerve impulses to muscle)
• poliomyelitis (an infectious disease that damages motor neurons)
• periodic paralysis (potassium related, such as hypokalemic periodic paralysis)

Home Care: Follow prescribed therapy for treating the underlying cause of the weakness.

Call If:

• there is weakness confined to one area of the body.
• there is prolonged, unexplained weakness or fatigue particularly if accompanied by other unexplained symptoms.

What To Expect: The medical history will be obtained and a physical examination performed.

Medical history questions documenting the weakness in detail may include:

• time pattern
  • When did the weakness begin?
  • Did it begin with an illness or injury?
  • Did it occur suddenly or gradually?
  • Is the weakness worse in the morning or at night?
  • Is the weakness noticed only after strenuous activity or exercise?
• quality
  • Is the weakness constant or does it come and go?
  • Does the weakness affect breathing?
  • Does it affect talking, chewing, or swallowing?
  • Does it affect walking, climbing stairs, sitting, getting up?
  • Does it affect use of the hands, arms, or shoulders?
  • Is there pain with the weakness?
  • Is there numbness or tingling with the weakness?
• location
  • Is the weakness limited to a specific area?
  • Has the area of weakness increased or decreased?
• aggravating factors
  • What makes the weakness worse?
    • physical activity
    • rest
    • hunger
    • fatigue
    • pain
    • stress
• relieving factors
  • Does anything help relieve the weakness?
    • rest
    • eating
    • pain relief
• other symptoms
  • What other symptoms are also present?
    • fever
    • injury
    • pain
    • numbness or tingling
    • vomiting
    • diarrhea
    • weight loss
    • headaches
    • changes in vision
    • change in skin color or temperature of the area affected
    • change in mental state, alertness, or responses
• additional important information
  • What medications are being taken?
  • Are there any known allergies?

• thyroid function tests
• blood tests such as a CBC and blood differential to check for anemia
• urine tests (urinalysis)
• X-rays (depending on the suspected cause)
• nerve conduction studies