Muscle weakness

Alternative names

Lack of strength; Weakness

Definition

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

Considerations

Weakness may be subjective (the person feels weak, but has no measurable loss of strength) or objective (measurable loss of strength as noted in a physical exam).

Weakness may be generalized (total body weakness) or localized to a specific area, side of the body, limb, or muscle.

A subjective feeling of weakness may be associated with infectious diseases such as infectious mononucleosis and influenza.

Weakness is more notable 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

• Addison's disease
  
• Thyrotoxicosis
  

NEUROLOGIC

• Stroke (often localized weakness)
  
• Bell's palsy (weakness of one side of the face)
  
• A nerve impingement syndrome such as a slipped disk in the spine
  
• Multiple Sclerosis (may be localized)
  
• Amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease; localized developing to generalized)
  
• Cerebral palsy (localized weakness associated with spasticity)
  
• Guillain-Barre syndrome
  

PRIMARY MUSCULAR DISEASES

• Muscular dystrophy (Duchenne)
  
• Becker muscular dystrophy
  
• Myotonic dystrophy
  
• Dermatomyositis
  

TOXIC