Weakness - Overview

Alternative Names

Lack of strength; Muscle weakness

Definition of Weakness:

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

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. For example, you may feel weak if you have infectious diseases such as mononucleosis and the flu.
Objective means there is a measurable loss of strength noted during a physical exam.

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

Reviewed last on: 8/8/2009
Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

References

Griggs RC, Józefowicz RF, Aminoff MJ. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 418.

Barohn RJ. Muscle diseases. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 447.

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