MEDIAN NERVE

INTRODUCTION:
  • Median nerve or "labourer's nerve" (C5, C6,C7, C8,T1)
  • Formed from the branches of medial and lateral cord of brachial plexus.
  • No branches to axilla & arm.
  • 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
SUPPLIES:
Sensory Supply
  • Palmar aspect:- Lateral half of Palm & Lateral fingers with their nail beds(anesthesized in surgeries related to nail bed)
  • Dorsal aspect: - distal part of Later 3 fingers
Motor Supply
  • FOREARM:

  1.  All flexors except flexor carpi ulnaris and medial half of flexor digitorum profundus
  2. Superficial volar forearm group 
  3. Pronator teres 
  4. Flexor carpi radialis
  5. Palmaris longus
  6. Intermediate group
  7. Flexor digitorum superficialis
  8. Deep group
  9. Flexor digitorum profundus (lateral)
  10. Flexor pollicis longus
  11. Pronator quadratus
  • HAND:
  1. 1st and 2nd lumbricals
  2. Opponens pollicis
  3. Abductor pollicis brevis
  4. Flexor pollicis brevis
  5. note: Adductor pollicus will not be affected in median nerve palsy
  6. Interosseous nerve is the branch of median nerve
  7. Injuries to Median nerve:
  • At elbow
  1. Pointing Index (detected by Oschner clasping test)(index finger anaesthesia)
  2. Simian/Ape thumb deformity (Thenar muscles wasted)
  3. Pen test
  • At wrist: (Most common in lunate bone dislocation)
  • Abduction & Opposition of thumb is lost.
  • Median Nerve- Commonly injured in cut injury at flexor retinaculum.
  • Commonly gets involved in entrapment neuropathy (carpal tunnel syndrome)
  • Tested by contraction of abductor pollicis brevis(pen test)
TEST OF MEDIAN NERVE LESION:
  • Tinel's sign- percussion of flexor retinaculum tingling sense in the distribution of median nerve.
  • Phalen's test- hyperextension/ flexion aggravates pain a paresthesia
  • Cuff compression test of Gilliatt & Wilson- BP cuff is inflated above systolic BP aggravates pain & paresthesia.
  • Ape thumb deformity
CLINICAL CONDITION:
  • Carpal Tunnel Syndrome:
  1. Caused by the compression of the median nerve at wrist and is most common type of nerve entrapment syndrome
  2. Infiltration of the transverse carpal ligament with amyloid (as occur in multiple myeloma) or thickening of connective tissue in rheumatoid arthritis, acromegaly, amyloidosis, mucopolysaccharidosis and hypothyroidism are less common cause of the syndrome.
  3. The syndrome is essentially a sensory one; the loss or impairment of superficial sensations affect the palmar aspect of the thumb. Index and middle fingers (especially the index finger) and may or may not split the ring finger. So the lateral three and half fingers are involved (not medial 3 1/2 fingers). The paresthesia are characteristically worsen during night.
  • AIN Neuropathy
  • Pronator Syndrome: inability to pronate arm
Exam Question
  • 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

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