Median Nerve
Deep Medicine

Origin

Course
1. Arm:
• Enters the arm from axilla at the inferior
margin of Teres Major muscle.
• No major branches in the arm.
• A branch to pronator teres may originate
immediately proximal to the elbow joint.

2. Forearm:
• Exits cubital fossa between the humeral and
ulnar heads of Pronator Teres
• Innervates all the muscles of anterior
compartment except Flexor Carpi Ulnaris and
the medial part of the Flexor Digitorum
Profundus.

Anterior Interosseus Nerve
• Largest branch of the median nerve in the
forearm
• Originates between the two heads of the
pronator teres.
• Passes distally down the forearm and innervates
the muscle in the deep layer (Flexor Pollicis
Longus, lateral half of Flexor Digitorum
Profundus, and the Pronator Quadratus).

Palmar Branch (Palmar Cutaneous Branch):
• A small branch of median nerve originates
from the median nerve in the distal forearm
immediately proximal to the carpal tunnel.
• Innervates the skin over the base and central
palm.

3.Hand:
• Enters hand by passing through the carpal tunnel
and divides into a Recurrent branch and Palmar
digital branches.
• The recurrent branch innervates three thenar
muscles.
• Palmar digital nerves innervate skin on palmar
surfaces of lateral three and a half digits and
cutaneous regions over the dorsal aspects of
distal phallanges of the same digits

• In addition to skin, the digital nerves supply
the lateral two lumbrical muscles.

Median Nerve Injury
• Low lesions
• High lesions

Low lesions
Site Cause Effect
At the level of Wrist
Joint
Carpal Tunnel Syndrome
Carpal Dislocations
•Paralysis of the Three thenar
muscles and the lateral two
lumbricals
•Patient unable to abduct the
thumb.
•Sensation over the lateral three
and half digits lost.
•In long standing cases thenar
eminence is wasted, thumb may
come to lie in the plane of palm
(Ape thumb Deformity)

High lesions
Site Cause Effect
At elbow or
forearm area
Elbow dislocation,
Supracondylar
humerus fracture
•All muscles supplied by median nerve
paralyzed
•The signs are the same as those of low
lesions but in addition, the long flexors to
the thumb, index and middle fingers, the
radial wrist flexors and the forearm
pronators paralysed.
•Pointing index sign
•Pinch defect ( OK sign)
•Sensation over the palm and the lateral
three and half digits lost.

Sites of Medial Nerve Compression
1. Carpal Tunnel Syndrome
Phalen’s Test Tinel’s test

2. Pronator syndrome:
i. Ligament of Struthers
ii. Bicipital Aponeurosis
iii. Fibrous bands between the deep and
superficial heads of the Pronator Teres.
iv. Fibrous Arch of Flexor Digitorum Superficialis

3. Anterior Interosseous Nerve Syndrome:
• Spontaneously (Parsonage-Turner Syndrome)
or fracture, fibrous bands, tumours
• Gantzer’s muscle

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