- The median nerve is also called labourer’s nerve.
- The median nerve is a peripheral nerve originating at the brachial plexus from the lateral and medial cords of the ventral roots of C6, C7, C8 and T1.
MUSCLES SUPPLIED BY MEDIAN NERVE:
1) In the forearm
- All the flexor muscles of the forearm, except the flexor carpi ulnaris & the medial half of flexor digitorum profundus to the ulnar two fingers.
These muscles are:
- Pronator teres
- Flexor carpi radialis
- Palmaris longus
- Flexor digitorum superficialis
- Flexor digitorum profundus[FDP] (lateral half)
- Flexor pollicis longus[FPL]
- Pronator quadratus
NOTE: FDP (lateral half), Pronator quadratus, FPL are muscles of deep compartment of forearm, & supplied by anterior interosseous branch of median nerve. Other muscles are supplied directly by median nerve.
2) In hand
- Median nerve supplies:
i) Thenar muscles (except adductor pollicis):
- Flexor pollicis brevis
- Opponens pollicis
- Abductor pollicis brevis
- Adductor pollicis is supplied by ulnar nerve
ii) First two lumbricals
SENSORY SUPPLY BY MEDIAN NERVE:
- Lateral two thirds of palm
- Lateral three & half fingers on palmar side & distal phalanx of lateral three & half digits on dorsal side.
MEDIAN NERVE INJURY
- In the arm– It is injured, though rarely by cut injury with a sharp object.
- At the elbow– It is commonly injured in the case of supracondylar fracture of humerus & dislocation of elbow.
- At the wrist– The median nerve is often injured by cut injury due to knife or glass.
- In carpal tunnel– Pressure from a dislocated lunate bone can damage the nerve. Compression neuropathy (i.e. Carpal tunnel syndrome)is more common than injury.
Muscles examination of median nerve injury
- From proximal to distal, the following muscles can be examined:-
1. Flexor pollicis longus:
- The patient is asked to flex the terminal phalax of the thumb against resistance while the proximal phalanx is kept steady by the examiner.
2. Flexor digitorum superficialis & lateral half of flexor digitorum profundus:
- If the patient is asked to clasp his hand, the index finger will remain straight, so-called ‘pointing index’.
- This occurs because both the finger flexors, superficialis as well as profundus of the index finger are paralysed.
3. Flexor carpi radialis:
- Normally, the palmar flexion at the wrist occurs in the long axis of the forearm.
- In a patient with paralysed flexor carpi radialis, the wrist deviates to the the ulnar side while palmar flexion occurs.
4. Muscles of the thenar eminence:
- Out of the three muscles of the thenar eminence, only two can be examined for their isolated action. There are as follows:-
i) Abductor pollicis brevis:
- The action of this muscle is to draw the thumb forwards at right angle to the palm.
- The patient is asked to lay his hand flat on the table with palm facing the ceiling.
- A pen is held above the thumb & the patient is asked to touch the pen with tip of his thumb.
- This is called ‘pen test’.
ii) Opponens pollicis:
- The function of this muscle is to appose the tip of the thumb to other fingers.
- Apposition is a swinging movement of the thumb across the palm & not a simple adduction.
- Median nerve is also known as labourer’s nerve
- Formed from the branches of medial and lateral cord of brachial plexus.
- Medial most structure in cubital fossa
- Deep to pronator teres heads
- Lateral to axillary artery in axilla
- Passing deep to flexor retinaculum at wrist
- seen in supracondylar # humerus
- Median nerve supplies nail beds(anesthesized in surgeries related to nail bed)
- Median nerve supplies Pronator teres of forearm
- Median nerve supplies Opponens pollicis muscle of hand
- Adductor pollicus will not be affected in median nerve palsy
- Interosseous nerve is the branch of median nerve
- Pointing Index seen in median nerve palsy
- Thenar muscle is wasted in median nerve palsy
- Median nerve injury is Most common in lunate bone dislocation among all carpel bones
- Median nerve injury at wrist is Tested by contraction of abductor pollicis brevis(pen test)
- Ape thumb deformity observed in median nerve injury
- Carpal Tunnel Syndrome seen in median nerve injury
- Median nerve injury results in inability to pronate arm