Brachial plexus

brachial plexus

1. The brachial plexus

2. The brachial plexus Formation Supraclavicular portion Trunks Divisions Infraclavicular portion Cords Branches

3. The brachial plexus The brachial plexus is a network of nerves that supply the upper limb

4. The brachial plexus extends from the neck into the axilla

5. Formation It is formed by five roots from the anterior (ventral) primary rami of C5,6,7,8, and T1

6. Formation the roots of the brachial plexus should not be confused with the ventral and dorsal roots which unite to form the spinal nerves dorsal & ventral roots of a spinal n. The ventral rami form the roots of the brachial plexus

7. Supraclavicular portion The roots lie in the neck between scalenus anterior and scalenus medius muscles Scalenus anterior Scalenus medius

8. Supraclavicular portion C5 & C6 unite to form the upper trunk

9. Supraclavicular portion C8 & T1 unite to form the lower trunk

10. Supraclavicular portion C7 continues as the middle trunk

11. Trunks of the brachial plexus The trunks lie in the posterior triangle of the neck and can be felt in the angle between the clavicle and sternocleidomastoid muscle sternocleidomastoid clavicle

12. Trunks of the brachial plexus The inferior trunk lies on the first rib posterior to the subclavian artery Inferior trunk

13. Divisions of the brachial plexus Behind the clavicle, each trunk divides into anterior and posterior divisions

14. Trunks of the brachial plexus the anterior divisions supply anterior (flexor) parts while the posterior divisions supply posterior (extensor) parts of the upper limb

15. Infraclavicular portion The three posterior divisions unite to form the posterior cord Posterior cord

16. Infraclavicular portion the anterior divisions of the upper and middle trunks unite to form the lateral cord lateral cord

17. Infraclavicular portion the anterior division of the lower trunk continues as the medial cord medial cord

18. Cords of the brachial plexus The cords are arranged around the second part of the axillary artery as indicated by their names.

19. Branches of the brachial plexus Each cord of the brachial plexus divides into a number of branches, 2 of them are terminal

20. Branches of the brachial plexus there are also a number of supraclavicular branches

21. Branches of the roots Dorsal scapular (C5) which supplies rhomboids muscles and levator scapula

22. Branches of the roots Nerve to subclavius (C5 & 6) which descends in front of the brachial plexus and the subclavian artery in the neck, it may give a contribution to the phrenic nerve (C5) this branch, when present is called the accessory phrenic nerve.

23. Branches of the roots The third branch is the long thoracic nerve (C5,6, & 7) descends behind the brachial plexus and supplies serratus anterior muscle

24. Suprascapular nerve From the upper trunk arises the suprascapular nerve

25. Suprascapular nerve The suprascapular nerve passes laterally across the neck, then through the suprascapular notch in the scapula to supply supraspinatus and infraspinatus muscles

26. Infraclavicular branches The infraclavicular branches are derived from the cords Each cord divides into 2 terminal branches.

27. Branches of the lateral cord The lateral cord has 3 branches mainly the lateral pectoral nerve and 2 terminal branches, the musculocutaneous and the medial root of the median nerve

28. Lateral pectoral nerve The lateral pectoral nerve pierces the clavipectoral fascia to supply pectoralis major muscle

29. Lateral pectoral nerve sends a communicating loop to the medial pectoral nerve, through which it supplies pectoralis minor muscle Axillary a. Pectoralis minor medial pectoral n. laterall pectoral n. Medial cord lateral cord posterior cord Axillary v. communicating loop

30. Musculocutaneous nerve pierces coracobrachialis muscle, supplying it before doing so

31. Musculocutaneous nerve it then supplies the muscles of the flexor (anterior) compartment of the arm mainly biceps and brachialis therefore it is known as the BBC nerve

32. Musculocutaneous nerve It ends by becoming the lateral coetaneous nerve of the forearm

33. Lateral root of the median nerve The lateral root of the median nerve is the direct continuation of the lateral cord

34. Median nerve The median nerve arises by medial and lateral roots from the corresponding cords of the brachial plexus

35. Median nerve the medial root crosses the axillary artery to join the lateral root so the median nerve is formed at first lateral to the axillary artery.

36. Median nerve The median nerve has no branches in the axilla and is responsible for the supply of the flexor compartment of the forearm and the palm.

37. Branches of the medial cord The medial cord has 5 branches the ulnar nerve and medial root of the median nerve are its two terminal branches Ulnar n.

38. Medial pectoral nerve The medial pectoral nerve passes through pectoralis minor supplying it then it supplies pectoralis major Axillary a. Pectoralis minor medial pectoral n. laterall pectoral n. Medial cord lateral cord Axillary v. axillary a. axillary v. Medial pectoral n. Pectoralis major

39. Medial cutaneous nerve of arm The medial cutaneous nerve of the arm, is a small nerve that runs medial to the axillary vein and supplies the skin over the medial side and front of the arm Axillary a. Axillary v.

40. Medial cutaneous nerve of arm communicates with the intercostobrachial nerve

41. medial cutaneous nerve of the forearm runs between the axillary artery and vein and supplies skin of the medial side of the forearm Axillary a. Axillary v.

42. medial cutaneous nerve of the forearm Runs between the axillary artery and vein superficial to the ulnar nerve

43. Ulnar nerve is the largest branch of the medial cord runs between the axillary artery and vein but at a more posterior plane than the smaller medial cutaneous nerve of the forearm Axillary a. Axillary v.

44. Ulnar nerve receives a branch from the lateral cord in more than 90% of cases has no branches in the axilla is mainly concerned with the innervation of the palm.

45. Medial root of the median nerve crosses the axillary artery to form the median nerve lateral to the artery Axillary a. Axillary v.

46. Branches of the brachial plexus Note that the musculocutaneous, median, and ulnar nerve form the letter M, which serves as the key to the brachial plexus

47. Branches of the posterior cord The posterior cord of the brachial plexus has 5 branches the axillary and radial nerves are its 2 terminal branches.

48. Upper and lower subscapular nerves The upper and lower subscapular nerves supply the upper and lower parts of subscapularis muscle

49. Lower subscapular nerve the lower subscapular nerve supplies teres major muscle in addition to suscapularis

50. Thoracodorsal nerve Runs between the subscapular nerves, it runs down on subscapularis towards latissimus dorsi which it supplies, it accompanies the subscapular vessels.

51. Axillary nerve It is inappropriately named since it supplies nothing in the axilla The first thing it does is to quit the axilla by passing backwards through the posterior wall of the axilla

52. Axillary nerve It leaves the axilla through the quadrangular space accompanied by the posterior circumflex humeral vessels just below the capsule of the shoulder joint to which it sends an articular branch (so it is sometimes called the circumflex nerve )

53. Axillary nerve It winds around the surgical neck of the humerus deep to deltoid muscle which it supplies, it also supplies teres minor, and the upper lateral cutaneous nerve of the arm

54. Radial nerve The radial nerve provides the major nerve supply of the extensor muscles of the upper limb (arm and forearm)

55. Radial nerve It lies behind the axillary artery on the glistening tendon of latissimus dorsi muscle latissimus dorsi tendon

56. Radial nerve posterior cord triceps (long head) posterior cutaneous of arm triceps (medial head) Branches in the axilla

57. Radial nerve It leaves the axilla posteriorly through a triangular space between the humerus, teres major, and the long head of triceps

58. Variants of normal anatomy – Expanded plexus Prefixed plexus – substantial contribution from C4 with small T1 contribution. Postfixed plexus – Major T2 contribution with small C5 contribution.

59. Brachial plexus injuries Etiologies traffic accidents birth injuries humerus luxations brachial plexus neuritis stab and bullet wounds tumors (especially lung cancer) cervical rib, fibrous band from C7 ( neurogenic thoracic outlet syndrome)

60. Principles of Localization Certain sites are prone to nerve entrapments/injuries Nerve opposing bone Ulnar nerve at the elbow Closed spaces Carpal tunnel Adjacent structures Median nerve at the elbow, adjacent to the brachial artery

61. Principles of localization (cont.) Order in which branches arise Movements at specific joints Single nerve Elbow extension Radial Multiple nerves Elbow flexion Musculocutaneous Radial

62. Brachial Plexus Injuries Upper Lesions of the Brachial Plexus ( Erb’s Palsy): resulting from excessive displacement of the head to opposite side and depression of shoulder on the same side.

63. This causes excessive traction or even tearing of C5 and 6 roots of the plexus. It occurs in infants during a difficult delivery or in adults after a blow to or fall on shoulder.

64. Effects : Motor : paralysis of the supraspinatus, infraspinatus , subclavius , biceps brachii , part of brachialis, coracobrachialis ; deltoid teres minor. Sensroy : sensory loss on the lateral side of the arm .

65. Deformity : waiter tip postion limb will hang by the side, medially rotated by sternocostal part of the pectoralis major; pronated forearm (biceps paralysis)

66. Erb-Duchenne palsy (waiter's tip)

67. Lower Lesions of the Brachial Plexus ( Klumpke Palsy) traction injuries by excessive abduction of the arm i.e. occurs if person falling from a height clutching at an object to save himself or herself. Can be caused by cervical rib. T1 is usually torn (ulnar and median nerves)

68. Motor Effects: paralysis of all the small muscles of the hand. Sensory effects : loss of sensation along the medial side of the arm. deformity: claw hand caused by hyperextension of the metacarpophalangeal joints and flexion of the interphalangeal joints.

69. Axillary Nerve injury Causes : crutch pressing upward into the armpit, Downward shoulder dislocations fractures of the surgical neck of the humerus.

70. Motor effects : Deltoid paralysis teres minor paralysis. Sensory effects : loss of sensation at lower ½ of deltoid Deformity : Wasting of deltoid

71. Radial Nerve injury Injury in axilla : crutch pressing up into armpit drunkard falling asleep with one arm over the back of a chair. fractures of proximal humerus.

72. Motor effects : paralysis of triceps Anconeus extensors of the wrist Extensors of fingers. Brachioradialis supinator muscle Deformity : Wrist and finger drop

73. Sensory effects : small area of sansation loss at arm and forearm sensory loss over lateral part of the dorsum of the hand (lat. 3.5 fingers without distal phalynges)

74. Injuries at Spiral Groove Caused by fracture shaft of humerus. Motor effects : paralysis of extensors of the wrist Extensors of fingers

75. Deformity : Wrist and finger drop Sensory effects : anesthesia is present over the dorsal surface of the hand (lat. 3.5 fingers)

76. Median Nerve injury Motor effects : paralysis of pronator muscles long flexor muscles of the wrist and fingers, Exception : flexor carpi ulnaris medial half flexor digitorum profundus .

77. Deformity : apelike hand thenar muscles wasted thumb is laterally rotated and adducted. index and to a lesser extent the middle fingers tend to remain straight on making Weakening of lat. 2 fingers

78. Sensory: Sensory loss on the lat. 3.5 fingers on palmar side Sensory loss over distal phalynges of lat. 4 fingers on dorsal surface

79. Ulnar nerve injury Motor effects: paralysis of flexor carpi ulnaris medial half of the flexor digitorum profundus All interossei 3-4 lumbricals loss of abduction and adduction of fingers Wasting of hypothenar

80. Deformity : partial claw hand Sensory effects : Sensory loss over 1.5 fingers on both surfaces

81. CARPAL TUNNEL TUNNEL FORMED BETWEEN THE CONCAVITY OF THE CARPAL BONES AND A LIGAMENT THAT COVERS THIS( FLEXOR RETINACULAM) TENDONS OF THE FLEXORS PASS THROUGH MEDIAN NERVE ALSO PASSES THROUGH CROWDED TUNNEL CARPAL TUNNEL SYNDROME CAUSED DUE TO COMPRESSION OF THE NERVE IN THE TUNNEL CAUSES - 1. SWELLING OF THE TEDONS( OVERUSE) 2. PREGNANCY( EDEMA) 3. ARTHRITIS SYMPTOMS - TINGLING OR NUMBNESS-LATERAL PART OF HAND, WEAKNESS IN THUMB MOVEMENT TREATMENT - REST, SPLINTING,ANTI-INFLAMMATORY DRUGS, SURGERY

82. Classification of Brachial plexopathies 1)Supraclavicular(root and trunk) – Upper plexopathy (upper trunk and root) Middle plexopathy (middle trunk & root) Lower plexopathy(lower trunk and root) 2)Retroclavicular (division) 3)Infraclavicular(cords and nerves)

83. Classification of Brachial plexopathies Supraclavicular with regional predilection 1) Upper plexus 1) Burner syndrome 2) Rucksack paralysis 3) Classic post – operative paralysis 2) Middle plexus – No isolated pathology

84. Lower Plexus 1) True neurogenic TOS 2) Post op disputed neurogenic TOS 3) Paramedian sternotomy plexopathy 4) Pancoast syndrome Other supraclavicular plexopathies . - Root avulsions. - Obstetric Brachial plexopathy

85. Site nonspecific brachial plexopathies 1) Neuralgic amyotrophy 2) Neoplastic brachial plexopathies 3) Radiation induced. 4) Traumatic 5) Iatrogenic

86. Supraclavicular vs infra Supraclavicular More common More often caused by closed traction injuries – more lengthy lesions More severe Worse outcome

87. Upper plexopathy vs lower Upper plexopathy More commonly due to demyelinating conduction block Recovery better Less axonopathy Located closer to the muscles Lesion mostly extraforaminal (amenable to surgical repair)

88. Evaluation of Brachial plexus History and Clinical examination Electrophysiological tests. Imaging and other ancillary tests – angiogram, myelogram etc

89. Clinical evaluation History Initial and subsequent symptoms – esp pain Circumstances Trauma – sports, injections, accident obstetrical Rucksack, Post – operative H/o malignancy or radiation

90. Clinical evaluation If trauma - what was the arm position on impact? Arm by side of body – C5, C6 Arm parallel to ground – C7 Arm above shoulder – C8 T1 Past medical history Family history

91. Examination Look for wasting with weakness – axonopathy vs demyelinating. Pattern of deficits Supraclavicular – segmental Infraclavicular – more in territory of multiple peripheral nerves of diff segments.

92. Vascular assessment – carotid and radial pulse. Any expanding mass, bruit or thrill near injury site Concomitant injuries – fractures of bones Examine breast, lungs and for lymphnodes

93. Electrodiagnostic assessment Advantages over clinical 1) Better localisation and characterisation 2) Subtle involvment in clincally normal muscle 3) To prove continuity when visible muscle movement is lacking. 4) Clinically inaccessible muscles 5) Estimate lesion severity for current and future comparisons.

94. Being a complicated structure, no single study can localize or characterize the lesion. Requires extensive NCS and NEE A regional approach may make it more simpler.

95. Electrodiagnostic tests Nerve conduction studies Motor Sensory Needle Electrode Examination

96. General principles in EP Pathophysiologically 1) Axonal – loss of continuity of axon – Wallerian degeneration-conduction failure. More severe lesion 2) Demyelinating - Conduction block or conduction slowing.

97. Axon loss lesions Most common pathology in BP. Mostly in isolation (avulsion, neoplasm) Occasionally with demyelination (radiation plexopathy, traumatic)

98. Edx features of axon loss lesions Reduced CMAP/SNAP amp with preserved CV and latencies. Absolute decrease in amp – less than normal for lab Relative decrease in amp - < 50 % of amp on C/L side.

99. NEE Most sensitive indicator of motor axonal loss. To know the proximal extend of lesion (where nerves are difficult to assess) To know continuity and identify early reinnervation when there is no muscle movement clinically.

100. A regional approach What will be the electrodiagnostic features if each element of the brachial plexus is taken seperately? Muscle domain of element CMAP/SNAP domain

101. The muscle domain of a brachial plexus element – muscles innervated by the motor fibers contained within it. CMAP/SNAP domain – motor and sensory fibers contained within that element and whether they are assessable by NCS. CMAP domains are a subset of muscle domains.

102. Treatment Most injuries recover without any Rx Rx is done in very highly specialized centers Surgical options nerve transfers nerve grafting muscle transfers free muscle transfers neurolysis of scar around the brachial plexus in incomplete lesions.