Radial Nerve

Radial nerve
- origin and root value
  - from brachial plexus ( posterior fibers )
    - as a terminal branch of posterior cord
  - C5, C6, C7, C8 and T1
- Course
  - Arm
    - travels behind 3rd part of axillary artery
    - runs behind brachial artery
    - enters lower triangular space
      - to reach radial sulcus of back of humerus
        
        here it gives muscular branches to triceps brachii
      - after emrgence from radial sulcus
        
        it gives brachialis, brachioradialis and extensor carpi radilis longus
      - travels together with profunda brachii artery
        
        between lateral and medial head of triceps
        
        until it reaches lateral side of arm
        
        5 cm below deltoid tuberosity it pierces
        
        intermuscular septum to reach anterior compartment of arm
        
        descends down to cross lateral epicondyle of humerus
        
        terminates by dividing
        
        superficial branch
        
        deep branch
  - Cubital fossa
    - superficial and deep branch continue in cubital fossa
  - Forearm
    - superficial ( sensory ) branch
      - passes along front of the radial side of forearm
      - at first lies
        
        slightly lateral to radial artery concealed beneath brachioradialis
      - in middle third of forearm
        
        lies behind same muscle
      - in lower forearm 7 cm above wrist
        
        passes beneath tendon of brachioradialis
        
        divides in to
        
        medial branch
        
        communicates
        
        above wrist
        
        with the dorsal branch of the lateral antebrachial cutaneous
        
        back of hand
        
        dorsal branch of the ulnar nerve
        
        then divides in to four digital nerves
        
        first supplies ulnar side of thumb
        
        second radial side of index finger
        
        third - adjoining sides of index and middle fingers
        
        fourth -
        
        lateral branch
        
        supplies the radial (lateral) side of thumb
        
        ball of thumb
    - Deep branch ( motor ) or posterior interosseus nerve
      - winds to the back of forearm
        
        around lateral side of radius
        
        between two planes of fibers of supinator
        
        prolonged downwards to middle of forearm
        
        supplies motor muscles in posterior compartment
        
        extensor compartment
      - clinical
        
        wrist drop due to paralysis to posterior cord
        
        Radial dislocation
        
        injury to deep branch of radial nerve
        
        wrist drop

Injury
- Injury to the radial nerve at different levels causes different syndromes with varying motor and sensory deficits.
- AT THE AXILLA
  - Common mechanisms of injury: Saturday night palsy,crutch palsy, lesions
  - Motor deficit:
    - Loss of extension of forearm, weakness of supination, and loss of extension of hand and fingers.
    - Presence of wrist drop, due to inability to extend the hand and fingers.
  - Sensory deficit: Loss of sensation[8] in lateral arm, posterior forearm, the radial half of dorsum of hand, and dorsal aspect of radial 3+1⁄2 digits, excluding their nail beds.
- AT MIDARM
  - Common mechanism of injury: Mid-shaft humeral fracture
  - Motor deficit:
    - Weakness of supination, and loss of extension of hand and fingers.
    - Presence of wrist drop, due to inability to extend the hand and fingers.
  - Sensory deficit: Loss of sensation in posterior forearm, the radial half of dorsum of hand, and dorsal aspect of radial 3+1⁄2 digits, excluding their nail beds.
- JUST BELOW ELBOW
  - Common mechanism of injury: Neck of radius fracture, elbow dislocation or fracture, tight cast, rheumatoid nodules, injections due to tennis elbow, injuring the deep branch of the radial nerve that pierces the radial head, causing posterior interosseous nerve syndrome
  - Motor deficit:
    - Weakness in extension of hand and loss of extension of fingers.
    - Presence of finger drop, and partial wrist drop, since the extensor carpi radialis longus and brachioradialis muscles are working.
  - Sensory deficit: None, as sensation is supplied by the superficial radial nerve
- WITHIN DISTAL FOREARM
  - Common mechanism of injury: Wartenberg's syndrome, (not to be confused with Wartenberg's sign), due to nerve entrapment beneath the tendinous insertion of brachioradialis, tight jewellery, and watch bands.
  - Motor deficit: None
  - Sensory deficit: Numbness and tingling in radial half of dorsum of hand, and dorsal aspect of radial 3+1⁄2 digits, excluding their nail beds.
  - In Wartenberg's syndrome, there is significant radial wrist pain, and close resemblance to symptoms in de Quervain's tenosynovitis. Finkelstein's test may be positive