Weakness

Alternative names:

lack of strength; muscle weakness

Definition:

A reduction in the strength of one or more muscles.

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

NEUROLOGIC

• 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)

PRIMARY MUSCULAR DISEASES

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

TOXIC

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

OTHER

• 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)

Note: There may be other causes of weakness. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as location, quality, time course, aggravating factors, relieving factors, and associated complaints. Use the Symptom Analysis option to explore the possible explanations for weakness, occurring alone or in combination with other problems.