Updated: 4/10/2017

Upper Extremity Innervation

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  • A 52-year-old female presents to her primary care physician with a chief complaint of pain and tingling in the right distal forearm and right hand. She has had these symptoms for several years but they have slowly been getting worse. At the beginning she would only have mild intermittent pain after waking or after long drives, but recently she feels that the symptoms have been almost constant and have interfered with her ability to live a normal life. Physical exam reveals weakness and loss of fine touch sensation in the lateral 3 and 1/2 fingers of her right hand and tapping on the wrist reproduces the symptoms. She is diagnosed with carpal tunnel syndrome and referred to a surgeon for consultation about a release.
Overview
 
 
Pathologies of Roots and Trunks of Brachial Plexus
  • Brachial Plexus
    • roots
      • C7 root can be compressed by 
        • cervical disk lesion
    • trunks
      • upper trunk can be damaged by  
        • birth trauma
        • traction on head during delivery of infant
        • lesions can cause Erb's palsy
      • lower trunk can be compressed by
        • extra cervical rib
        • pancoast lung tumor
        • compression causes
        • catching self on arm while falling (grabbing tree branch to break fall)
        •  Klumpke's palsy
Pathologies of Terminal Branches of Brachial Plexus
  • General compression syndromes can result in pain, paresthesias, or weakness of the innervated muscle groups
  • Musculocutaneous nerve
    • in arm
      • compressed by
        • brachialis muscle sheath
        • coracobrachialis muscle
    • in cubital fossa
      • compressed by
        • bicepital aponeurosis
  • Median nerve 
    • in cubital fossa
      • compressed by
        • supracondylar fracture of humerus
        • pronator teres syndrome
    • in wrist
      • compressed by
        • carpal tunnel syndrome
        • dislocated lunate
    • in forearm
      • anterior interosseous nerve, a branch of median nerve, compressed in deep forearm
    • in hand
      • recurrent branch of median nerve lesioned by superficial laceration
  • Ulnar nerve 
    • in cubital fossa
      • lesioned by
        • repeated minor trauma
        • fracture of medial epicondyle of humerus
    • in hand
      • lesioned by
        • trauma to heel of hand
        • fracture of hook of hamate
  • axillary nerve
    • lesioned by
      • fracture of surgical neck of humerus
      • dislocation of humerus
      • intramuscular injections
  • radial nerve
    • in axilla
      • compressed by incorrect use of crutches
    • in spiral groove of humerus
      • lesioned by midshaft fracture of humerus
    • in forearm
      • deep branch of radial nerve stretched by subluxation of radius
Dermatomes of Upper Limb

 

 

Innervation of Hand
  • HandHand
    • median nerve
      • passes through carpal tunnel with 9 tendons
      • palmar cutaneous branch of median nerve supplies skin of central palm
      • recurrent branch of median nerve supplies thenar muscles
      • cutaneous branches of median nerve supply skin of radial 3.5 digits
    • ulnar nerve
      • cutaneous branch of ulnar nerve supplies skin of base of medial palm
        • branches via ulnar before ulnar nerve enters hand
      • ulnar nerve passes through Guyon's canal to hand
      • deep branch of ulnar nerve supplies interossei muscles and adductor pollicis

 

 

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