Anatomy of Brachial plexus

Anatomy ,clinically relavant for the anaesthesiologist

1. ANATOMY, A LAUNCH PAD FOR RA! UPPER EXTREMITY ANATOMY DR KALPESH SHAH M.D.,D.A (Anaesthesia ) Consultant Anaesthesiologist Mumbai

2. “The understanding of innervations are of basic importance and is the basis for Neuro-electrostimulation .” Dr Sandip Diwan (Regional Nerve Blocks book)

3. Brachial plexus block becomes the analogues to epidural anaesthesia, i.e. once the compartment is entered ,a single injection of an adequate volume of local anesthetic results in successful anaesthesia.

4. BRANCHES OF BRACHIAL PLEXUS

5. DERMATOMES

6. SCHEMATIC DIAGRAM OF BRACHIAL PLEXUS

7. GROSS ANATOMICAL RELATION OF BRACHIAL PLEXUS AT NECK

8. DISSECTION AT NECK

9. DISSECTION OF NECK

10. ORIENTATION OF ‘ BRACHIAL LINE’

11. SCLEROTOME (ANT.)

12. SCLEROTOME (POST.)

13. DIVISIONS Each trunk divides to form an anterior and posterior division posterior to the mid clavicle. In general, anterior divisions supply muscles of the anterior compartments (flexors) where as the posterior division supply muscles of the posterior compartments(extensors) No branches arises from the divisions.

14. The dorsal rami course posteriorly into the spinal extensors (erector spine)and do not contribute to the brachial plexus. The ventral rami of C4 & C5 also contribute to the brachial plexus The ventral ramus of T1 also contribute to the first intercostal nerve.

15. DISSECTION AT THE LEVEL OF CORDS

16. INTERSCALENE BLOCKS

17. The ant scalene muscle arises from anterior tubercle of the transverse process of the 3 rd,4 th,5 th and 6 th cervical vertebra. It inserts on the scalene tubercle of the first rib. Brachial plexus is situated lateral and superior to the subclavian artery.

18. Middle scalene muscle arises from the posterior tubercles of the transverse process of lower six cervical vertebrae. The trunks that are stacked on each other now divides into anterior and posterior division are enclosed in the scalene sheath and come to lie superolateral to the subclavian artery.

19. The topography changes from almost vertical arrangement of trunks of brachial plexus to a horizontal one. Quiet often, the trunks are short in length and divide and rejoin immediately at the supraclavicular area(division ), thus at times the interscalene or supraclavicular produces mixed neurostimulation induced evoked muscle response.

20. PREVERTEBRAL FACIA The prevertebral fascia of the neck extends down to ensheth the axillary artery and cords. It is this axillary sheath that local anesthetic is injected when performing the brachial plexus block

21. Once the needle tip penetrates the prevertebral cervical fascia its really undecided whether the tip is in the interscalene groove or in the anterior or middle scalene muscle. Increasing resistance on bolus injection will suggest the tip in the muscle ,while a smooth flow will be definitive that tip is in the groove.

22. ANATOMICAL VARIATIONS Commonly described anatomical relationship of brachial plexus lying between the anterior scalene and middle scalene muscle was found in only 60% of instance. The most common variation was the penetration of AS by the C5 and/or C6 ventral rami.

23. The C5 &C6 roots may fuse before piercing Anterior Scalene. ( 15%cases). The C5 root alone pierce the belly of AS (13%cases) The C5 root was found completely anterior to AS in 3% of cases.

24. VERTEBRAL FORAMEN IS AT A DISTANCE OF 3.7 CMS APPROX FROM SKIN…..BEWARE OF INTRAFORAMINAL INJECTION

25. SYMPATHETIC CHAIN BLOCKADE WITH ISB CAN CAUSE BRONCHOSPASM DUE TO UNOPPOSED VAGAL PARASYMPATHETIC ACTION

26. HEAD ROTATION MORE THAN 30 DEGREES DISTORTS THE ANATOMICAL GROOVE AND VASCULAR RELATIONSHIP INTERCOSTOBRACHIAL NERVE TO BE INFILTRATED FOR ANESTHESIA AROUND MEDIAL PART OF SHOULDER AND FOREARM

27. IMPORTANCE OF VARIATION IN ANATOMY No neurostimulation Inappropriate neurostimulation Appropriate neurostimulation but inadequate block Total block failure

28. The posterior cord is discrete in 25%,in 71% continues as various nerves and in 4% directly as the radial nerve.

29. The upper two roots join to form the upper trunk, this is C5-6 . This is exactly the position of the stimulating needle tip ,

30. The trunks lay above each other with sparse connective tissue between them . Drug injected at the upper trunk will slowly disperse along a concentration gradient.

31. The distance between the interscalene and the subclavian area is too small, drug injected correctly in the sheath will spread across the entire length from the cervical root to the supraclavicular area.

32. The scalene muscle and the brachial plexus are in same plan ,thus the needle should be perpendicular to this plane.

33. PHRENIC NERVE The phrenic nerve is in close relation to the trunks of brachial plexus in the inrerscalene area . It lies on the anterior scalene muscle and courses from the lateral aspect of scalene to the medial.

34. The higher level interscalene block ,the more the incidence of phrenic nerve block.

35. Contrast study showed, the spread of contrast is linear and compressed between the two scalene muscle and widens lower down at the midpoint of the clavicle . The contrast spreads close to the anterior scalene muscle thus blocking the phrenic nerve.

36. Combining low volume LA and digital pressure was thought to reduce incidence of phrenic nerve palsy.

37. SUPRASCAPULAR NERVE This nerve accompanies the trunks for a considerable distance and then leaves posteriorly through the middle scalene muscle .

38. Stimulation of the suprascapular nerve is possible and provides a false feeling of the needle tip in the sheath of brachial plexus.

39. One branch arises from the trunks . Suprascapular nerve, it arises from the upper trunk and supplies the supraspinatus and infraspinatus muscles, and sensation to the glenohumeral and acromioclavicular joints.

40. SUPRACLAVICULAR BLOCK

41. BLOCK IS AT THE LEVEL OF DIVISIONS BRACHIAL PLEXUS IS SUPPOSED TO BE COMPACT AT THIS LOCATION, DENSE ACTION EXPECTED

42. ANATOMICAL LANDMARK - SUBCLAVIAN ARTERY ( BP IS POSTEROLATERAL ) 0.5 -6 % CHANCES OF PNEUMOTHORAX VASCULAR INJURIES COMMON

43. INFRACLAVICULAR ANATOMY The divisions pass over the first rib close to the dome of the lung and continue under the clavicle as cords immediately posterior to the subclavian artery. The sheath is completely stripped off the infraclavicular cords.

44. The cords are identified according to their relationship to the axillary artery. The lateral cord lies more laterally and superficially and is first to be encountered during an infraclavicular block.

45. The lateral cord always lies anterior to either the posterior or medial cord and cranial to the axillary artery. The posterior cord was always cranial to the medial cord and both cords were always located dorsal to the artery.

46. There are at least 13 branches at infraclavicular area . The musculocutaneous nerve has an anomalous origin or connection to the median nerve in 11%,and a connection carrying C7 fibers from the lateral cord to the ulnar nerve occurs in 42% of anatomic specimens

47. The lateral root of the median nerve may pass posterior to the axillary artery and the axillary and radial nerves may arises directly from the division such that a true posterior cord is not present.

48. The musculocutaneous nerve (MCN) leaves the brachial plexus sheath high in the axilla at the level of the lower border of the teres major muscle and passes into the substances of coracobrachialis muscle .

49. The MCN exits out of the lateral cord early in the course and is reliably blocked in infraclavicular area.

50. AXILLARY BLOCK

51. BLOCK GIVEN AT THE LEVEL OF CORDS ANATOMICAL LANDMARK – AXILLARY ARTERY CORDS SURROUND THE ARTERY IN 2’O CLOCK TO 11’O CLOCK POSITION

52. VASCULAR INJURIES VERY COMMON TOO MEDIALLY DIRECTED NEEDLE INCREASE THE CHANCE OF PNEUMOTHORAX

53. TARGETTING POSTERIOR CORD STIMULATION GIVES EQUAL SPREAD TO ALL THE CORDS FINGER/WRIST – FLEXION / EXTENSION AS END POINT OF NEUROSTIMULATION

54. BICEPS CONTRACTION SUGGESTIVE OF MUSCULOCUTANEOUS…DO NOT ACCEPT AS THIS NERVE EXITS THE PLEXUS BEFOREHAND TOURNIQUET PAIN POSSIBLE WITH PLAIN AXILLARY BLOCK

55. AXILLARY NERVE It supplies the shoulder joint, the surgical neck of humurus, the deltoid, and the teres minor muscle before ending as the superior lateral brachial cutaneous nerve, which innervates the superolateral part of proximal arm.

56. AXILARY AREA DISSECTION

57. My sincere thanks to Dr. A vadhoot K ulkarni

58. THANK YOU