The Axilla and Brachial plexus
Prof. AO Ihunwo, PhD School of Anatomical Sciences
1 Lecture Outline
Axilla Brachial Plexus Introduction Spinal Nerves – formation & Boundaries Importance Contents Brachial Plexus Formation & Components Relations Branches Clinical Implications/Injuries
2 Introduction
Pyramidal space between upper limb & thorax Communicates with posterior triangle of neck Transmits neurovascular structures & lymph vessels/nodes
3 Boundaries
Anterior: Pectoralis major & minor, subclavius & clavipectoral fascia Posterior: Teres major, subscapularis, Latissmus dorsi Lateral: Humerus: upper part of shaft with intertubercular groove Medial: Serratus anterior (4-5 digitations), intercostal muscle at 4th intercostal space Floor (Base): Axillary fascia and skin Apex: Bounded by clavicle, scapula, outer border of 1st rib; directed towards root of neck Contents of Axilla
Medial wall: Lateral thoracic vessels, lateral branches of 2-4 intercostal Nn, Long thoracic N Posterior Wall: Subscapular vessels, posterior circumflex humeral vessels, Axillary N, Upper & Lower Subscapular Nn, Thoracodorsal N. Lateral wall: Medial cut. N of arm, axillary vein, medial cut. N of forearm, Ulnar N, 3rd part of axillary artery, medial root of median N, median N, musculocutaneous N, posterior cord Other structures: Axillary lymph nodes, fat Principles of Limb Plexuses - Introduction
Nerves that form Limb plexuses arise from spinal cord Spinal Cord Long cylindrical structure. Av. Length in adults – 45 cm Extent: Foramen magnum to lower border of L1 vertebra. Diameter varies at different levels Presents 2 enlargements Cervical (C3 to T2) innervates upper limb & Lumbar (L1 to S3) innervates lower limb
6 Spinal Nerves C1
Spinal nerves consist of C5 8 Cervical (C1 – C8)
12 Thoracic (T1 – T12) T1 5 Lumbar (L1 – L5) 5 Sacral (S1 – S5) T12 1 Coccygeal (Co1)
L5 Note that there is a connection between all ventral rami of spinal nerves Co1
7 Formation of spinal nerve from dorsal & ventral roots
Dorsal ramus: – innervates skin muscles & connectives tissue of back
Ventral ramus:– Form nerve plexuses
8
Importance of spinal nerves Dermatomes are areas of sensory innervation on skin for each spinal nerve
c3
c7 c6 T3 c8 T1
Ventral
c3 c5 T3 c6 T1 c8
Dorsal
9 Importance of spinal nerves
Myotome refers to muscle(s) that one particular spinal root supplies
Importance Diagnosis of neurological disorders lesions of nerve roots result in typical patterns of neurologic defects (muscle weakness, loss of sensation) that allow localisation of causating lesion Referred pain, especially dermatomes
10 Brachial Plexus
Network of nerves from spinal cord that controls muscle movements & sensation in Upper limb Components Roots Trunks Divisions Cords Branches
11 Formation of Brachial Plexus
Roots (5): Ventral rami of C5 C6 C1 C7 C8 T1
Prefixed brachial plexus: C5 C4 – C8. Large contribution from C4 with T2 absent & T1 reduced in size
Postfixed brachial plexus: C6 – T2. T1 Large contribution from T2 with C4 absent & C5 reduced in size
12 Trunks & Divisions
Trunks (3) Superior trunk: C5 & C6 Middle trunk: continuation of C7 Inferior trunk: C8 & T1 Divisions (6) Each trunk splits into anterior (3) & posterior (3) divisions
13 Cords (3)
Lateral cord: anterior divisions of upper & middle trunks
Medial cord: anterior division of lower trunk
Posterior cord: posterior divisions of upper, middle & lower trunks
14 Relations of components
Roots: Between anterior & middle scalene muscles
Trunks: Cross posterior triangle of neck
Divisions: Behind the clavicle
15 Relations of components…
Cords: Lie in axilla
Named according to their relation with 2nd part of axillary artery
Lateral Medial Posterior
16 Supraclavicular Branches
Roots: Muscular (scalene & longus colli muscles) Dorsal scapular nerve Long thoracic nerve Contribution from C3 to Phrenic nerve (C3-C5) Trunks: Nerve to subclavius Suprascapular nerve
17 Infraclavicular Branches (13)
Lateral cord (3) lateral pectoral musculocutaneous lateral head of medial nerve Posterior cord (5) axillary nerve upper subscapular middle subscapular (thoracodorsal) lower subscapular radial nerve
18 Infraclavicular Branches…
Medial cord (5) medial cutaneous nerve of arm medial cutaneous nerve of forearm medial pectoral medial head of median nerve ulnar nerve
19 Distribution of Supraclavicular Branches
From Nerve Roots Muscles Cutaneous rhomboid muscles & Roots Dorsal scapular C5 - levator scapulae C5, Long thoracic C6, Serratus anterior - C7 superior Nerve to C5, subclavius - trunk subclavius C6 C5, Supraspinatus & Suprascapular - C6 Infraspinatus
20 Distribution of Infraclavicular Branches
From Nerve Roots Muscles Cutaneous pectoralis major & Lateral lateral C5, C6, pectoralis minor (by - cord pectoral C7 communicating with medial pectoral nerve) coracobrachialis, Musculo- C5, C6, lateral cutaneous brachialis & biceps Cutaneous C7 nerve of forearm brachii Lateral head C5, C6, (root) of fibres to median nerve - C7 median nerve
21 Distribution of Infraclavicular Branches…
Medial Medial Pectoralis minor & C8, T1 - cord pectoral pectoralis major Medial head portions of hand not served (root) of C8, T1 fibres to median nerve by ulnar or radial median nerve Medial front & medial skin cutaneous C8, T1 - of arm nerve of arm Medial cutaneous C8, T1 - medial skin of forearm nerve of forearm flexor carpi ulnaris, skin of medial side of hand, medial 2 bellies of medial 1½ fingers on flexor digitorum Ulnar C8, T1 palmar side profundus, medial 1½ fingers on most of small muscles dorsal side of hand
22 Distribution of Infraclavicular Branches…
Posterior Upper C5, C6 Subscapularis (upper part) - cord subscapular Middle C6, C7, subscapular Latissimus dorsi - C8 (thoracodorsal) Lower lower part of subscapularis C5, C6 - subscapular & teres major anterior branch: deltoid & a posterior branch small area of overlying skin becomes upper lateral Axillary C5, C6 posterior branch: teres cutaneous nerve of minor & deltoid muscles arm C5, C6, Triceps brachii, anconeus, skin of posterior arm Radial C7, C8, extensor muscles of forearm as posterior cutaneous T1 & brachioradialis nerve of the arm
23 Clinical Implications
Brachial plexus injuries falls on side of head/shoulders (violent stretching of nerves) traction (forceps delivery) pressures leading to incomplete injuries.
Cords rarely damaged by direct injury except gunshots & stab wounds.
Efforts to reduce a shoulder joint dislocation could also produce brachial nerve injuries.
24 Brachial Plexus Injuries
Superior trunk Injury (Erb-Duchenne paralysis) Upper trunk stretches or tears Erb’s point Waiter’s tip position hanging extended (flexors paralyzed), in medial rotation (lateral rotators paralyzed)
25 Brachial Plexus Injuries…
Inferior trunk injury Klumpke’s paralysis ‘clawed hand’ deformity
Anesthesia on medial surface of arm & hand & paralysis/atrophy of muscles innervated by ulnar nerve
26 Brachial Plexus Injuries …
Crutch Paralysis Pressure from usage of crutches Mostly affects radial & Ulnar ‘Wrist drop’ deformity
Sleep palsy: Pressure on radial nerve with subject asleep under influence of alcohol or some narcotics. ‘Saturday night palsy’ Usually temporary 27 Brachial Plexus Injuries …
Winging of the scapula Long thoracic nerve. A ‘winged’ appearance on the back. Inability to raise arm or carry out pushing movements Cervical rib syndrome Presence of a cervical rib (C7) may put pressure on lower trunk
28 Questions
What structures form the boundaries of the axilla. List the contents of the axilla Draw a well labelled diagram of the brachial plexus (No description required) Describe the formation of the brachial plexus from the roots to the cords. Describe the origin and distribution of the ulnar nerve. What are the effect of injury to the nerve at the epicondyle. [Could also be median or radial nerves] Describe the brachial nerve injuries
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