18-01-21 - Nerves of the Upper Limb Flashcards
What is anastomosis around the scapula formed by?
Anastomosis around the scapula is formed by 2 branches of the subclavian artery, and 1 or 2 branches of the 3rd part of the axillary artery
The suprascapular and dorsal scapular arteries are branches of the subclavian which come over the top of the scapula
Anteriorly coming round, we have the subscapular artery with its important branch, the circumflex scapular artery, which passes onto the posterior surface of the scapula, and anastomoses with the other 2 branches
Where does the brachial artery start?
The brachial artery starts at the lower border of teres major
Where is the origin of the ulnar and radial arteries?
- Ulnar and radial arteries have varying points of origin due to variable bifurcation
Where are the interosseus arteries located?
- The interosseus arteries run between the radial and ulnar bones
Where are radial and ulnar palpable?
- The radial and ulnar arteries are both palpable at the wrist
What do both the radial and ulnar artery have at the wrist? What do these contribute to?
- At the wrist, both radial and ulnar arteries have palmar (anterior) and dorsal (posterior) carpal branches at the wrist. (each artery has a branch on either side of the wrist)
- These arteries contribute to palmar and dorsal carpal arches, along with branches from the interosseus arteries
What does the ulnar artery form when it enters the hand?
- When the ulnar artery enters the hand, it gives off a deep branch, which continues as the superficial branch, and arches across the palm of the hand to create the superficial palmar arch
Where does the radial artery enter into the hand? What does the radial artery form when it is doing this?
- The radial artery passes posteriorly on the scaphoid and trapezium of the wrist, then re-enters the palmar surface of the hand through the 1st dorsal interosseus muscle (radial artery goes from anterior, to posterior, to anterior)
- When doing this, the radial artery forms the deep palmar arch, which anastomoses with the deep branch of the ulnar
Where is there good collateral supply?
- There is good collateral supply around highly moveable joints
Where do deep veins follow?
- Deep veins follow the arterial supply mostly, and share the same names as the arteries
How do they exist distally?
- Distally, deep veins don’t normally exist by themselves, they are venae comitantes, and we will normally find 2 or 3 veins rapped around the equivalently named artery
Where do the brachial veins come together?
- The brachial veins coalesce (come together to form one mass or whole) into the axillary vein
What is the other vein the brachial veins also come together with?
- The brachial veins are joined by the basilic vein in the axillary vein at the lower border of the teres major
What does the axillary vein join with?
What does this then join with?
- The axillary vein then joins with the jugular veins to become the subclavian vein.
- The subclavian vein joins with the
brachiocephalic vein to from the superior vena cava
What are superficial veins named after?
- Superficial veins have their own identities
How do numbers of veins and arteries compare in the axilla?
- In the axilla (armpit), veins are more numerous and variable than arteries
What do superficial lymphatics of the upper limb follow?
- Superficial lymphatics follow the superficial veins
What does the brachial plexus supply? Is it sensory and motor?
- The brachial plexus is the nervous supply to the upper limb, including all but 1 extrinsic back muscle
- Contains both sensory and motor components
What are dermatomes?
- Dermatomes are areas of skin innervated by a spinal segment
How are nerves different from dermatomes supplying the skin?
- Dermatomes are not the same as nerves suppling the skin
- Individual named nerves that come out of the brachial plexus can supply different areas of different dermatomes
- Different dermatomes can be represented by more than 1 nerve
What are myotomes?
- Myotomes are a group of muscles innervated by a single spinal segment, usually with a common action
What are the two compartments of arm and the forearm?
What do muscles in each compartment have?
- The two compartments of the arm are the anterior and posterior compartment
- The two compartments of the forearm are the anterior and posterior compartments
- The muscles in each compartment have the same (named) nerve supply (usually), and have a common action
- A compartment, a nerve, an action (roughly)
Where does the brachial plexus emerge from?
- The brachial plexus emerges from between the scalenus medius and the scalenus anterior muscles in the root of the neck
Where are the roots of the brachial plexus found?
- The roots of the brachial plexus are found deep in the neck between the scalenus anterior and scalenus medius muscles
How many roots form how many trunks?
What does each trunk divide into?
Where do these divisions take place?
What 3 ways do these divisions come together?
What do they form?
What are the 2 reasons we change from superior and middle in the trunks to medial and lateral in the cords?
- 5 roots become 3 trunks
- Each trunk has an anterior and posterior division (3 trunks become 6 divisions)
- These divisions take place behind the clavicle
• These divisions come together 3 ways:
1) The anterior division of the superior and middle trunk come together to form the lateral cord
2) All of the posterior divisions come together to form the posterior cord
3) The anterior division of the inferior trunk continues on by itself to form the medial cord
• 2 reasons we change from superior and middle in the trunks to medial and lateral in the cords:
1) We have come out sideways, and we are now starting to turn round the corner of the limb
• That which was superior is now medial, that which was inferior is now lateral
2) The axillary artery also comes through this area
• The cords are named for their relative position to the axillary artery
What are the 5 main terminal branches of the brachial plexus?
What shape do these terminal branches form?
• 5 main terminal branches of the brachial plexus:
1) Musculocutaneous nerve
2) Median nerve
3) Radial nerve
4) Axillary nerve
5) Ulnar nerve
• These terminal branches form an M-shape, which is a useful reference point
What do each of the terminal branches of the brachial plexus supply (sensory and motor)?
1) Musculocutaneous nerve
- Sensory
- Lateral cutaneous nerve of the forearm
- Motor
- Anterior compartment muscles of the arm
2) Median nerve
- Sensory
- 1/2 skin of the palm
- Motor
- Anterior compartment muscles of the forearm (except 1 ½)
- Thenar muscles of the hand
3) Radial nerve
- Sensory
- Posterolateral skin of the forearm
- Dorsal skin of the hand
- Motor
- Posterior compartment muscles of the arm
4) Axillary nerve
- Sensory
- Skin of supra-lateral arm
- Motor
- Deltoid and teres minor muscle
5) Ulnar Nerve
- Sensory
- ½ skin of the hand
- Motor
- 1 ½ muscles of anterior forearm
- Rest of small muscles of the hand
What are the roots associated with each of the major branches of the brachial plexus?
1) Musculocutaneous nerve – C5-C7
2) Axillary nerve – C5 and C6
3) Median nerve – C6 to T1
4) Radial nerve – C5 to T1
5) Ulnar nerve – C7, C8 and T1
What are 2 minor branches of the brachial plexus not involved in the innervation of the upper limb?
What nerve roots do they contain? What do they supply?
What are 5 more minor branches that do not come off the posterior or medial cord?
• Minor branches of the brachial plexus not involved in the innervation of the upper limb:
1) Phrenic nerve
• Contains nerve roots C3, C4 and C5
• Supplies the diaphragm
2) 1st intercostal nerve
• Supplies rib space 1
• 5 more minor branches that do not come off the posterior or medial cord:
1) Long thoracic nerve
• Takes origin from C5, C6 and C7
• Passes down behind the roots very medially
• Passes down the lateral aspect of the thoracic wall, supplying a muscle called the serratus anterior
• Runs along side the lateral thoracic artery (branch of axillary artery)
• Relatively easy to find in mid-axillary line
• Don’t want to damage while doing chest drains
2) Dorsal scapular nerve • Comes off C5 • Very proximal • Can be difficult to find • Comes off between scalene muscles
3) Suprascapular nerve
• Goes down the same way the suprascapular artery does, except when it reaches the suprascapular notch, it goes underneath and upper transverse scapular ligament
• The suprascapular artery goes over the top and around the suprascapular foramen
4) Subclavian nerve
• Supplies one muscle underneath the clavicle
• Very small and difficult to find
5) Lateral pectoral nerve
• Supplies one of the pectoral muscles
• Comes from the lateral cord
What are the 3 minor branches of the posterior cord of the brachial plexus?
What are the 3 minor branches of the medial cord of the brachial plexus?
• 3 minor branches of the posterior cord of the brachial plexus:
1) Upper scapular nerve
• Supplies muscles like subscapularis
2) Thoracodorsal nerve
• Supplies latissimus dorsi
3) Lower subscapular nerve
• Supplies more of subscapularis
• 3 minor branches of the medial cord of the brachial plexus:
1) Medial pectoral nerve
• Supplies pectoral muscles
2) Medial brachial cutaneous nerve
3) Medial antebrachial cutaneous nerve
• Both of these supply the skin on the medial side of the arm
What are the two main causes of brachial plexus injury?
What roots does an upper brachial plexus injury affect?
What 3 things will the patient be unable to do?
What 3 things will the upper limb present with?
What is this position known as?
What condition does upper brachial plexus injury cause?
What roots does a lower brachial plexus injury affect?
How does this affect the hand?
What condition does this lead to?
- The 2 main causes of brachial plexus injury are obstetric (relating to childbirth) and traumatic
- An upper brachial plexus injury tends to result in the injury of roots of C5 and C6
• The patient will be unable to:
1) Flex elbow (C5 and C6)
2) Laterally rotate elbow
3) Abduct shoulder
• The upper limb will present: 1) Adducted 2) Internally rotated 3) Extended at the elbow • This position is known as waiters tip palsy • This causes Erb’s Palsy
- A lower brachial plexus injury tends to be injury to C8 and T1
- This leads to problems with intrinsic muscles of the hand, leading to movements being difficult, and the hand ending up like a claw
- This condition is known as Klumpkey’s Palsy
What are 3 more minor branches or the brachial plexus?
• 3 more minor branches of brachial plexus
1) Intercostal brachial nerve
• T2
• Cutaneous (beneath skin) in axilla
2) Nerve to subclavius
• Small muscle that anchors and stabilises clavicle
3) Suprascapular nerve
• Goes through suprascapular foramen (N on diagram)
• Suprascapular artery (A on diagram) above the upper transverse scapular ligament, nerve below
What is the median nerve closely associated with?
What is the axillary nerve closely associated with?
What is the radial nerve closely associated with?
• The median nerve is closely associated with the supracondylar region in the distal humerus
• The axillary nerve is closely associated with the surgical neck of the humerus
• The radial nerve is closely associated with the spiral groove on the lateral surface of the humerus
Where are anastomosis present?
Anastomosis are present around all joints, which allows for collateral flow, should the main vessel be compromised
What is the difference between anastomosis and collateral flow?
An anastomosis is a physical connection between 2 vessels which allows for the [physiological concept of collateral flow
Collateral flow goes through an anastomosis
Where does the brachial artery pass down?
The brachial artery passes down the arm medially
Where does the brachial artery end?
- It ends at its bifurcation (division) anterior to the elbow, which is variable, and can take place as high up as the elbow
What are the terminal branches it splits into?
- The brachial artery’s termina branches are the ulnar and radial arteries
What are the 3 branches of the brachial artery (other than ulnar and radial) splits into?
1) Profunda brachii
* Passes behind the humerus
* Anastomoses with the radial recurrent and middle collateral artery
2) Superior ulnar collateral
3) Inferior ulnar collateral
* Both of these anastomose with the anterior and posterior ulnar recurrent
How do the ulnar and radial arteries compare to each other?
- The ulnar is larger and deeper than the radial
