Median nerve

anatomy and median nerve entrapment syndromes

1. MEDIAN NERVE Dr.HARSHA NANDINI TALASILA M.S Ortho

2. Branch of lateral and medial cord of the brachial plexus. In the arm it lies lateral to the brachial artery. In the middle of the arm it crosses the artery from lateral to medial side and remains on the medial side upto the elbow.

3. In the arm: branch to the elbow joint and vascular branch to the brachial artery. In the cubital fossa it lies medial to the brachial artery. It enters the forearm by passing between the 2 heads of the pronator teres. In the forearm it passes beneath the fibrous arch of flexor digitorum superficialis and on the surface of flexor digitorum profundus.

4. About 5cm above the flexor retinaculum it becomes superficial and lies between the tendons of flexor carpi radialis and FDS. It is overlapped by the tendon of palmaris longus . Median nerve enters the hand by passing deep to flexor retinaculum through the carpal tunnel.

5. Muscular branches to all the superficial flexors of forearm except FCU Anterior interosseous nerve is given off in the upper part of the forearm,it supplies the flexor pollicis longus,the lateral half of FDP and pronator quadratus DRUJ and wrist joints

6. Branches in the hand MOTOR BRANCHES Abductor pollicis brevis Flexor pollicis brevis Opponens pollicis 1 st and 2 nd lumbricals SENSORY SUPPLY Lateral 3½ digits on palmar side and distal half of dorsal surface

7. INJURY TO MEDIAN NERVE Median nerve is injured near the wrist or high up in the fore arm. High median nerve palsy Low median nerve palsy

8. HIGH MEDIAN NERVE PALSY Injury proximal to the elbow. Stabs and gunshot wounds 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

9. LOW MEDIAN NERVE PALSY Injury in the distal third of the forearm Cuts in front of wrist or by carpal dislocation There will be sparing of the forearm muscles , but the muscles of the hand will be paralysed There will be anaesthesia over the median nerve distribution in the hand

10. Thenar eminence is wasted and thumb abduction and opposition are weak. Sensation is lost over the radial three and half digits.

11. TESTS FPL: the patient is asked to flex the terminal phalanx of the thumb against resistance while the proximal phalanx is kept steady by the examiner.

12. OSCHNER’S CLASPING TEST FDS and lateral half of the FDP: if the patient is asked to clasp his hand,the index finger will remain straight,the so called pointing index. This occurs because both the finger flexors (FDS and FDP)are paralysed but the medial half of the FDP makes flexion of the others fingers possible.

13. FCR: normally the palmar flexion at the wrist occurs at in the long axis of the forearm. In the patient with paralysed flexor carpi radialis,the wrist deviates to the ulnar side while the palmar flexion occurs.

14. ABDUCTOR POLLICIS BREVIS: the patient is asked to lay his hand flat on the table with palm facing the ceiling. A pen is held above the thumb and the patient is asked to touch the pen with tip of his thumb-PEN TEST

15. COMPRESSIVE NEUROPATHY

16. CARPAL TUNNEL SYNDROME Boundaries of carpal tunnel: Medial: hook of hamate and pisiform Lateral: scaphoid and trapezium Roof : flexor retinaculum The most palmar structure in the carpal tunnel is median nerve. Deep to the median nerve are present the long flexor tendons of thumb and fingers.

17. Entrapment of the median nerve at the wrist. CAUSES: Decrease in the size of the tunnel Bony abnormalities of the carpal bones Acromegaly .

18. Increase in the contents of the tunnel. Scaphoid or distal radius fractures Scaphoid subluxation or lunate dislocation Local tumors like ganglion,neuroma,lipoma Hematoma

19. Neuropathic conditions Diabetes mellitus Alcoholism Inflammatory conditions Rheumatoid arthritis Gout Infections

20. Alterations of fluid balance. Pregnancy Thyroid disease Renal failure Obesity Amyloidosis External forces. Vibration Direct pressure

21. TESTS DURKAN’S TEST: Compression is applied to the median nerve by the examiner for 30 seconds. Patients will have symptoms of numbness,pain,parasthesia in the region of median nerve distribution.

22. PHALEN’S TEST: Patient is asked to keep the wrist flexed continuously for 1 minute. Patient will have tingling and numbness in the lateral 3 and a half fingers.

23. GILIAC TEST: Arm torniquet is inflated above systolic pressure for 60seconds. Tingling and numbness in the median nerve distribution.

24. MANAGEMENT Splinting of the wrist in neutral position Corticosteroid injection into the carpal tunnel

25. SURGERY Constant parasthesias not relieving after conservative management Thenar atrophy Delayed median nerve conduction velocity on NCV

26. PRONATOR SYNDROME ETIOLOGY: Supracondylar process: On the anteromedial surface of the humerus,about 5cm above the medial epicondyle ,an aberrant spur of bone A ligament of struthers runs from spur to the medial epicondyle . Median nerve,brachial artery and vein run beneath this ligament.

27. CLINICAL FEATURES: Vague anterior forearm pain Sensory disturbances over the palmar cutaneous branch of the median nerve. Tenderness over the course of the median nerve in the forearm

28. Tests: PROXIMAL FOREARM COMPRESSION TEST Firm direct pressure is applied to the forearm at the elbow for 30 seconds. Pain in the forearm and sensory disturbance along the median nerve course.

29. TREATMENT NSAIDS ELBOW SPLINTING in 90 degree flexion and neutral forearm rotation

30. ANTERIOR INTEROSSEOUS SYNDROME Seen in athletes resulting from a violent muscle contracture from aggressive forearm exercises This syndrome involves motor loss without sensory involvement. AIN innervates: FDP,FPL,Pronator quadratus

31. CLINICAL FEATURES Inability to flex the thumb No complaint of parasthesias or sensory disturbances OK Sign/ Klien Nioh Sign TREATMENT : Surgical decompression

32. TENDON TRANSFERS BRANDS TECHNIQUE and BUNNELL PROCEDURE: FDS of ring finger to OPPONENS POLLICIS CAMITZ PROCEDURE :PALMARIS LONGUS to APB BURKHALTER TECHNIQUE: EXTENSOR INDICES PROPRIUS to OPPONENS POLLICIS

33. MUSCULOCUTANEOUS NERVE

34. Musculocutaneous nerve is a branch of lateral cord of the brachial plexus. COURSE : In the axilla it is present lateral to the axillary artery. It pierces the coracobrachialis and enters the anterior aspect of the arm. It runs downwards and laterally between the biceps brachii and brachialis muscles. It terminates as the lateral cutaneous nerve of the forearm.

35. Motor supply: Biceps brachii . Brachialis Coracobrachialis Sensory supply Lateral cutaneous nerve of the forearm: Skin over the lateral aspect of the forearm

36. Causes of injury: Penetrating injury Rarely by anterior dislocation of shoulder,fracture of humerus

37. Musculocutaneous neuropathy is rare Possible cause due to lifting heavy weights on the shoulder with the arm curled around the object: CARPET CARRIER’S PALSY. More common entrapment is the distal sensory nerve at the elbow between the biceps tendon and brachialis muscle.

38. Clinical features: Decreased sensation over the lateral aspect of the forearm. Wasting of biceps and brachialis . Motor loss is not significant as flexion of the elbow is also performed by brachioradialis

39. TREATMENT REST Corticosteroid injection Massages and manual exercises to release the fascial adhesions and any scar tissue in the muscle which are entrapping the nerve. Surgical decompression if symptoms persist more than 6months and donot respond to conservative management.

40. CAMPBELL’S OPERATIVE ORTHOPAEDICS NETTAR’S ATLAS OF HUMAN ANATOMY CHAURASIA TEXTBOOK OF ANATOMY

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