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Median Nerve.pptx

  1. Median Nerve Deep Medicine
  2. Origin
  3. 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.
  4. 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.
  5. 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).
  6. 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.
  7. 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
  8. • In addition to skin, the digital nerves supply the lateral two lumbrical muscles.
  9. Median Nerve Injury • Low lesions • High lesions
  10. 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)
  11. 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.
  12. Sites of Medial Nerve Compression 1. Carpal Tunnel Syndrome Phalen’s Test Tinel’s test
  13. 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
  14. 3. Anterior Interosseous Nerve Syndrome: • Spontaneously (Parsonage-Turner Syndrome) or fracture, fibrous bands, tumours • Gantzer’s muscle
  15. Thank You

Editor's Notes

  1. Formed Anterior to the third part of the axillary artery by the union of lateral and medial roots originating from lateral and medial cords of brachial plexus
  2. Median: Flexor Carpi Radialis, Palmaris Longus, Pronator Teres, Flexor Digitorum Superficialis (Superficial Compartment) AIN: Flexor Digitorum Profundus- Lateral Part, Pronator Quadratus, Flexor Policis Longus (Deep Compartment)
  3. Solely Motor Nerve
  4. Palmar cutaneous branch is spared in Carpal Tunnel Syndrome
  5. Recurrent Branch: Thenar Muscles (Flexor pollicis brevis, Opponens Policis, Abductor pollicis Brevis) Palmar digital branch: The lateral Two lumbricals and sensory supply
  6. Typically the hand is held with the ulnar fingers flexed and the index straight (the ‘pointing index sign’)
  7. Compression: First the median nerve is identified between flexor carpi radialis and palmaris longus, the nerve is compressed with both the thumbs with firm pressure for 30 seconds, intervel between pain, paresthesia or numbness is noted usually about 16 seconds in carpal tunnel syndrome. Phalen’s test:Both wrists in a fully flexed position for 1–2 minutes. The appearance or exacerbation of paraesthesia in the median distribution is suggestive of the carpal tunnel syndrome, and is positive in 70% of those suffering from this condition Tinel’s test:the test is positive if gentle finger percussion over the median nerve produces paraesthesia in its distribution. This test is said to be positive in 56% of cases of carpal tunnel syndrome.
  8. Ligament of Struthers: The ligament of Struthers connects the supracondylar process to the medial epicondyle, encasing the median nerve and brachial artery. It is seen in approximately 13% of the general population and rarely causes median nerve entrapment.
  9. Isolated AIN injury is rare. Spontaneous (and usually temporary) Physiological failure (Parsonage–Turner syndrome) is a more likely cause. There is motor weakness without sensory symptoms. Gantzer’s muscle: This is the accessory head of the FPL and has been postulated to be a cause of AINS ; in an anatomic study, the muscle was found in 52% of limbs and was supplied by the AIN, and it was found to be posterior to both the median nerve and the AIN in all cases
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