The median nerve arises from the C5-T1 nerve roots and forms in the axilla from the lateral and medial cords of the brachial plexus. In the arm, it runs laterally to the brachial artery before crossing anterior to the elbow. In the forearm, it passes deep between muscles before emerging in the palm. It innervates muscles of the thenar eminence and digits 1-3. Injuries can cause paralysis of forearm and hand muscles or isolated hand muscle weakness depending on injury level. Physical exam tests include Phalen's maneuver and Tinel's sign to check for carpal tunnel syndrome.

1. MEDIAN NERVE
Harshavarthini Parthiban

2.  Root value: C5, 6, 7,8 and T1
 Runs in the median plane of the forearm, so its called
median nerve
 Arises in the axilla by 2 roots
 Lateral (from lateral cord of brachial plexus)
 Medial root (from the medial cord of the brachial plexus)

3. IN AXILLA
 Median nerve is formed by lateral root from lateral cord and
medial root from medial cord of brachial plexus
 Median nerve runs lateral to axillary artery

4. IN ARM
 Median nerve continues to run on the lateral side of brachial
artery till the middle of arm, where it crosses infront of the
artery and passes anterior to the elbow joint into forearm

5. IN FOREARM
 Enters to the forearm between two heads of pronator teres
 Then deep to fibrous arch of flexor digitorum superficialis,
in proximal third
 In mid forearm, descends between flexor digitorum
superficialis and flexor digitorum profundus
 About 5cm above wrist, it comes to lie on the lateral side of
the flexor digitorum superficialis, becomes superficial just
above wrist

6. IN HAND
 Nerve passes deep to the flexor retinaculam and enters the
palm
 Muscular branches supply muscles of thenar eminence
(abductor pollicis brevis, opponens pollicis and flexor
pollicis brevis)

7.  Finally divides into 4 to 5 palmar digital branches supplying
lateral three and half digit and their nail beds.
 Also, motor branches are given to the first and second
lumbrical muscles

8. BRANCHES
 In arm: vascular branches to the brachial
 In forearm: muscular branches to all superficial flexor
muscles(pronator teres, flexor carpi radialis, palmaris longus and
flexor digitorum superficialis)
 Anterior interosseous, which comes off the median nerve supplies
lateral half of flexor digitorum profundus, flexor pollicis longus and
pronator quadratus
 Articular branches supply the elbow joint and proximal ulnar joint
 Palmar cutaneous branch supply skin over thenar eminence and
central part of palm

9. Role of median nerve:
 Motor Functions.
 The median nerve innervates the majority of the muscles in
the anterior forearm, and some intrinsic hand muscles.
 In the forearm, the median nerve directly innervates muscles
in the superficial and intermediate layers:
 Superficial layer: Pronator teres, flexor carpi radialis and
palmaris longus

10. INJURY TO THE MEDIAN NERVE:
 Median nerve is most commonly injured near the wrist or high
up in the fore arm
 1. high median nerve palsy
 2. low median nerve pasy

11. LOW MEDIAN NERVE PALSY:
 Injury in the distal third of the forearm
 Cuts infront of wrist or by carpal dislocation
 There will be sparing of the forearm muscles, but the muscles
of the hand will be paralysed
 Thenar eminence is wasted and thumb abduction and
opposition are weak
 Sensation is lost over the radial and half digits and changes
may be seen

12. HIGH MEDIAN NERVE PALSY:
 Injury proximal to the elbow
 Generally due to forearm features or elbow dislocation
 Trauma may damage the nerve at any level
 This will cause paralysis of all the muscles supplied by the
median nerve in the forearm and hand

13. FLEXOR POLLIS
LONGUS
This muscle is tested by
holding thumb at its
base and patient asked
to bend the terminal
phalanx

14. FLEXOR DIGITORUM
SUPERFICIALIS AND
PROFUNDUS
When the patient is
asked to clasp the hands
the index finger of
affected side fail to
reflex.
Ochsners clasping tes

15. FLEXOR CARPI
RADIALIS
The hand deviates to
ulnar side when it is
flexed against resistance

16. ABDUCTOR POLLICIS
BREVIS
The patient is asked to
lay his hand flat on the
table, a pen is held
above the palm and the
patient is asked to touch
the pen with his thumb
Pen test

17. OPPONENS
POLLICIS
Bring the tip of the
thumb towards the tips
of other fingers

18. PHALEN’S
MANEUVER
1. Diagnostic test for
carpal tunnel
syndrome
2. . A person holds his
or her forearms
horizontally and
then pushes backs
of the hands
together (inverse
praying position to
achieve maximal
wrist flexion)

19. TINEL’S SIGN
Tinel's sign is positive
when lightly banging
(percussing) over the
nerve elicits a sensation
of tingling, or 'pins and
needles,' in the
distribution of the nerve.

20. CARPAL
COMPRESSION TEST
Direct pressure over
transverse lig for 30
seconds