MEDIAN NERVE

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MEDIAN NERVE
- ORIGIN AND ROOT VALUE
  - formed by two heads in axilla
- COURSE
  - AXILLA
    - lies anterior to 3rd part of axillary artery ( काँख धमनी के सामने )
      - crosses artery from lateral to medial (
  - ARM
    - enters arm from axilla at inferior border of teres major muscle
    - passes vertically downwards and
      - courses lateral to brachial artery ( पार्श्व स्थान पर जाता हैं_ )
        
        between
        
        biceps brachii above
        
        brachialis below
      - then it crosses
        
        anteriorly to run medial to brachial artery ( फिर भुज धमनी के मध्य स्थान पर जाता हैं
  - in cubital fossa
    - lies medial to brachial artery
      - passes under biceps
      - on to or medial to brachialis
    - gives articular branch to elbow
  - in Forearm
    - then between two heads of pronator teres
      - deep to bicipital aponeurosis
      - superficial to brachialis muscle
    - crosses ulnar artery
      - separated by the deep head of pronator teres
    - then travels between
      - flexor digitorum superficialis above
      - flexor digitorum profundus below
    - then above 5cm above flexor retinaculum
      - merges between
        
        the flexor digitorum superficialis (medially)
        
        the flexor carpi radialis (laterally)
    - branches in forearm
      - supplies anterior compartment of forearm except
        
        flexor carpi ulnaris
      - muscular branches
      - anterior interosseus branches
  - in hand
    - Enters the hand through carpal tunnel
      - passes deep to flexor retinaculum to reach palm of hand
      - along with tendons
    - branches in hand
      - sensory
        
        palmar cutaneous branch leave median nerve above wrist
        
        runs superficial to flexor retinaculum
        
        supply lateral palm skin
      - motor
        
        lateral 2 lumbricals
        
        abductor pollicis brevis
        
        opponens pollicis
        
        flexor pollicis brevis

Injury
- Injury of median nerve at different levels causes different syndromes with varying motor and sensory deficits.
At the shoulder
- Injury can occur at the brachial plexus[9]
Above the elbow
Common mechanism of injury: a supracondylar humerus fracture
Motor deficit:
- Loss of pronation of forearm, weakness in flexion of the hand at the wrist, loss of flexion of radial half of digits and thumb, loss of abduction and opposition of thumb.
- Presence of an ape hand deformity when the hand is at rest, due to an hyperextension of index finger and thumb, and an adducted thumb
- Presence of benediction sign when attempting to form a fist, due to loss of flexion of radial half of digits
Sensory deficit: loss of sensation in lateral 3+1⁄2 digits including their nail beds, and the thenar area
At the elbow
- Entrapment at the level of the elbow or the proximal forearm could be due to the pronator teres syndrome.
Within the proximal forearm: anterior interosseous syndrome
- Injury to the anterior interosseous branch in the forearm causes the anterior interosseous syndrome
- Common mechanisms: tight cast, forearm bone fracture
- Motor deficit: loss of pronation of forearm, loss of flexion of radial half of digits and thumb
- Sensory deficit: none
At the wrist
- Common mechanism: wrist laceration
- Motor deficit:
  - Weakness in flexion of radial half of digits and thumb, loss of abduction and opposition of thumb
  - Presence of an ape hand deformity when the hand is at rest may be likely, due to an hyperextension of index finger and thumb, and an adducted thumb. Nevertheless, an ape hand deformity is not a requirement for a carpal tunnel syndrome diagnosis.
  - Presence of a benediction sign when attempting to form a fist, due to weakness in flexion of radial half of digits
- Sensory deficit: loss of sensation in lateral 3+1⁄2 digits including their nail beds, and the thenar area
Within the wrist: carpal tunnel syndrome
- Common mechanism: carpal tunnel syndrome, an injury by compression in the carpal tunnel, without transection of the median nerve, due to overuse by activities such as keyboard typing and cooking
- Motor deficit:
  - Weakness in flexion of radial half of digits and thumb, weakness in abduction and opposition of thumb
  - Presence of an ape hand deformity or when attempting to form a fist, the benediction sign, due to compression of the median nerve, as opposed to complete median nerve palsy
- Sensory deficit: numbness and tingling in lateral 3+1⁄2 digits including their nail beds, but excluding the thenar eminence which is supplied by the palmar cutaneous branch of the median nerve[10] Unlike in wrist laceration, sensation still occurs in the area of the central palm. Sensation is not lost because the palmar cutaneous branch runs above the flexor retinaculum, and is not affected in compression in carpal tunnel syndrome.