Health Encyclopedia

Weakness

Definition

Weakness is a reduction in the strength of one or more muscles.

Alternative Names

Lack of strength; Muscle weakness

Considerations

Weakness may be generalized (total body weakness) or localized to only one area, side of the body, limb, or muscle. Weakness is more notable when it is localized. Localized weakness may follow a stroke, flare up of multiple sclerosis, or injury to a nerve.

Weakness may be subjective or objective.

Subjective means you feel weak, but there is no measurable loss of strength.
Objective means there is a measurable loss of strength noted during a physical exam.

A subjective feeling of weakness may be associated with infectious diseases such as mono and the flu.

Common Causes

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

METABOLIC

Addison's disease
Hyperparathyroidism
Low sodium or potassium
Thyrotoxicosis

NEUROLOGIC

Amyotrophic lateral sclerosis
Bell's palsy
Cerebral palsy
Guillain-Barre syndrome
Multiple sclerosis
Pinched nerve (for example, caused by a slipped disk in the spine)
Stroke

PRIMARY MUSCULAR DISEASES

Becker muscular dystrophy
Dermatomyositis
Muscular dystrophy (Duchenne)
Myotonic dystrophy

TOXIC

Botulism
Organophosphate poisoning (insecticides, nerve gas)
Paralytic shellfish poisoning

OTHER

Home Care

Follow prescribed therapy for treating the underlying cause of the weakness.

Call your health care provider if

Call your doctor if you have:

Prolonged, unexplained weakness
Sudden weakness, particularly when it is in one area and not accompanied by other complaints, such as fever
Sudden weakness following a viral illness
Weakness in one area of the body

What to expect at your health care provider's office

The doctor will examine you and ask questions about your medical history and symptoms, such as:

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?
- Did it start following a typical viral illness, such as a cold?
- Did it start after a vaccination?
Quality
- Is the weakness constant or does it come and go, sometimes effecting different parts of your body?
- 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 do you have?
  - 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 responsiveness
Additional important information
- What medications do you take?
- Do you have any allergies?

Physical examination may include special attention paid to examination of heart, lungs, and thyroid gland. If there is a local area of weakness, the examination will focus on the nerve and muscle functions.

Diagnostic tests that may be done include:

Blood tests for autoimmune disorders
Blood tests such as a CBC and electrolytes
Lumbar puncture (CSF collection)
MRI or CT scan of your head and spine
Muscle biopsy
Nerve conduction studies
Thyroid function tests
Urinalysis

References

Olney RK. Weakness, Disorders of Movement, and Imbalance. In Kasper DL, Braunwald E, Anthony S. Fauci AS, eds. Harrison’s Internal Medicine. 16th ed. New York, NY: McGraw-Hill; 2005.

Review Date:7/17/2007
Reviewed By:Robert Hurd, MD, Professor of Endocrinology, Department of Biology, Xavier University, Cincinnati, OH, and physician in the Primary Care Clinic, Cincinnati Veterans Administration Medical Center, Cincinnati, Ohio. Review provided by VeriMed Healthcare Network.

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