Phalen's sign

A provocative test for carpal tunnel syndrome in which sustained maximal wrist flexion reproduces median nerve paresthesias or pain in the distal median nerve distribution, indicating compression of the median nerve within the carpal tunnel.

Causes of median nerve compression within the carpal tunnel

• Anatomical and structural causes

  • Narrow carpal tunnel anatomy

  • Wrist fracture or dislocation

  • Osteoarthritis-related bony changes

  • Ganglion cysts

  • Space-occupying lesions

  • Tendon sheath enlargement

• Inflammatory and systemic causes

  • Rheumatoid arthritis

  • Tenosynovitis

  • Inflammatory arthritis

  • Diabetes mellitus

  • Hypothyroidism

  • Amyloidosis

  • Chronic kidney disease requiring hemodialysis

• Pregnancy and hormonal causes causing increased tissue edema

  • Pregnancy-related fluid retention

  • Menopause-associated hormonal changes

• Occupational and mechanical causes

  • Repetitive wrist movements

  • Prolonged wrist flexion or extension

  • Vibrating tools

  • Manual labor

  • Computer-related repetitive strain

• Traumatic causes

  • Wrist trauma

  • Distal radius fracture

  • Post-traumatic swelling

• Other causes

  • Obesity

  • Genetic predisposition

  • Acromegaly

  • Congenital abnormalities of the carpal tunnel