18-01-21 - Nerves of the Upper Limb Flashcards
Learning outcomes
- Describe the Structure of the brachial plexus
- Describe features of the Brachial plexus – from roots to terminal branches
- Describe compartments of the upper limb in terms of their nerve supply
- Describe the dermatomes and myotomes of the upper limb
- Explain how different injuries of the brachial plexus may present
What is anastomosis around the scapula formed by?
Where are anastomosis present?
What is the difference between anastomosis and collateral flow?
- 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
- Anastomosis are present around all joints, which allows for collateral flow, should the main vessel be compromised
- 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 start?
Where does it pass down?
Where does it end?
What are the terminal branches it splits into?
What are the other 3 branches of the brachial artery splits into?
- The brachial artery starts at the lower border of teres major
- The brachial artery passes down the arm medially
- It ends at its bifurcation (division) anterior to the elbow, which is variable, and can take place as high up as the elbow
- The brachial artery’s termina branches are the ulnar and radial arteries
- The other 3 branches of the brachial artery:
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
Where is the origin of the ulnar and radial arteries?
How do these 2 arteries compare to each other?
What do both arteries have?
Where is the radial artery located throughout the forearm?
Where can it be found in the hand?
Where can the ulnar artery be found?
- Ulnar and radial arteries have varying points of origin due to variable bifurcation
- The ulnar is larger and deeper than the radial
- Both arteries have recurrent branches which take place in elbow anastomoses
- The radial has the radial recurrent and middle recurrent branches which anastomose with the profunda brachii
- The ulnar has anterior and posterior recurrent arteries, which anastomose with the superior and inferior collateral arteries
- In the forearm, the radial artery is anterior, but raps around from anterior to posterior at the wrist
- The radial artery can be found in the anatomical snuff box, which is a triangular depression fond on the lateral aspect of the dorsum (back) of the hand
- The ulnar artery remains anterior into the hand
Where are the interosseus arteries located?
What branch does the ulnar artery give off?
What does this split in to?
• The interosseus arteries run between the radial and ulnar bones
• The ulnar artery quickly gives a branch called the common interosseus, which bifurcates into:
1) The anterior interosseus
2) The posterior interosseus
• These two arteries run either side of the interosseus membrane down the forearm towards the hand
Where are radial and ulnar palpable?
Which is more palpable?
Do these arteries enter the carpal tunnel?
Where do these arteries pass at the wrist?
What is the Allen’s test used for?
What are 5 steps of the Allen’s test?
- The radial and ulnar arteries are both palpable at the wrist
- The radius is felt easier, as the radial lies just anterior to the distal radius
- Neither of these arteries enter the carpal tunnel, as we don’t want blood vessels going through an in expandable space
- The radial artery passes posteriorly to the carpal bones
- The ulnar artery passes anterior (superficially) to the flexor retinaculum (forms roof of carpal tunnel) in Guyon’s canal
- Allen’s test is used before sampling arterial blood for a blood gas
- If there is poor collateral flow, we don’t want to stab a needle into the arteries, so we may use the other hand
1) Compress the radial and ulnar arteries for s short period of time
2) The palm of the hand should go pale
3) Release 1 of the radial or ulnar arteries and the hand should regain colour
4) Repeat with the other artery
5) If the hand turns pink, there is good collateral flow between the radial and ulnar arteries
What do both the radial and ulnar artery have at the wrist?
What do these contribute to?
What are scaphoid fractures?
How are they caused?
What can they cause?
- 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
- Scaphoid fractures are found in and around the wrist
- They can be caused by falling onto an outstretched hand
- Scaphoid fractures can interrupt the blood supply coming in at the distal end of the forearm, leading to the proximal part undergoing avascular necrosis
Superficial arteries of the hand:
What does the ulnar artery form when it enters the hand?
What does this structure meet?
What does the superficial palmar arch give off?
What do these divide into?
• 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
• The superficial palmar arch meets the superficial palmar branch of the radial at the far end
• The arch gives off 3 common palmar digital arteries, which pass into the metacarpals of the hand
• These palmar digital arteries each divide into two proper palmar digital arteries, which go up adjacent sides of fingers before anastomosing at the tip of the finger
Deep arteries of the hand:
Where does the radial artery enter into the hand?
What does the radial artery form when it is doing this?
What does this structure give off?
What are 2 big important branches of our radial artery/deep palmar arch?
- 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
- The deep palmar arch gives off palmar metacarpal arteries, which anastomose with common palmar arteries
• 2 big important branches of our radial artery/deep palmar arch:
1) Radial indices artery – supplies the lateral aspect of the index finger
2) Princeps pollicis artery – supplies the thumb (why we don’t feel for patients’ pulse with our thumb – strong pulse present in our thumb)
Hand anastomoses.
Where is their good collateral supply?
What are hand arterioles important for?
What are 2 examples of important anastomoses in the hand?
- There is good collateral supply around highly moveable joints
- Hand arterioles are very important for thermal regulation
• Important anastomoses in the hand:
1) Deep palmar arch anastomosing to our common digital palmar arteries
2) Dorsal metacarpal arteries coming off dorsal carpal arch
Deep veins.
Where do deep veins follow?
How do they exist distally?
Where do the brachial veins come together?
What is the other vein they also come together with?
What does the axillary vein join with?
What does this then join with?
- Deep veins follow the arterial supply mostly, and share the same names as the arteries
- 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
- The brachial veins coalesce (come together to form one mass or whole) into the axillary vein
- The brachial veins are joined by the basilic vein in the axillary vein at the lower border of the teres major
- 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
Superficial veins.
What are superficial veins named after?
Where do they run in?
What are the cephalic and basilic vein formed from?
How do these veins communicate with one another?
What is the median cubital vein used for?
How does the basilic vein form venae comitantes?
How does the cephalic vein run up the arm?
What does it join with?
What does it run between?
- Superficial veins have their own identities
- The run in the superficial fascia
- The dorsal venus network (arch) gives the cephalic vein (lateral) and the basilic vein (medial)
- These veins communicate with each other at the cubital fossa (elbow region) via the median cubital vein
- The median cubital vein is used for venepuncture, as it is a pretty consistent structure, as it is attached to 2 large superficial veins
- The basilic vein pierces the deep fascia half way up the arm, where it will go to join the venae comitantes of the brachial artery to from the axillary vein
- The cephalic vein remains superficial all the way up until just below the clavicle, where it will pierce deep fascia, and join the axillary vein
- The cephalic vein runs in a groove between the deltoid and pectoralis major, known as the delto-pectoral groove
Central Venus System.
How do numbers of veins and arteries compare in the axilla?
Where do the veins flow?
What is present in the central venus system?
Where else does the axillary vein receive blood flow from?
What can this lead to?
- In the axilla (armpit), veins are more numerous and variable than arteries
- The veins closely follow but do not exactly follow arterial routes
- In the central venus system, there are frequent anastomoses
- The axillary vein also receives some body wall veins from the lower abdomen?
- This can lead to the spread of disease
Lymphatics of the upper limb.
What do superficial lymphatics follow?
What do deep lymphatics follow?
Where do all of these lymphatics drain to?
What are the 5 groups of lymph nodes located here?
What are 2 reasons why these lymph nodes important?
Where do superficial lymph nodes on the medal side of the upper limb drain?
Where do superficial lymph nodes alongside the cephalic drain?
Where do lymphatics alongside deep veins drain?
What can diseases of the upper limb be represented by?
What are other places the lymph nodes drain?
What is the pyramid of drainage for breast cancer metastases?
- Superficial lymphatics follow the superficial veins
- Deep lymphatics follow the deep veins, which are essentially the same route as the arteries
• All of these lymphatics drain up towards the axilla, where there are 5 groups of lymph nodes:
1) Humeral (aka lateral lymph nodes) – follow the basilic vein and deep veins
2) Pectoral (medial)
3) Subscapular (posterior)
4) Central
5) Apical – follow the cephalic veins
• These lymph nodes are important because:
1) They are palpable
2) The group of lymph nodes to which these various areas of the body drain to are very specific
- Superficial lymph nodes on the medial side of the upper limb drain to the lateral/humeral lymph nodes
- Superficial lymph nodes along side the cephalic vein (apical) drain tot eh apical lymph nodes
- Lymphatics running with deep veins drain towards the humeral lymph nodes
- Diseases of the upper limb could be represented by inflammation of the humeral/apical lymph nodes
- These lymph nodes also drain the body wall and the breast
- Breast cancer metastases head towards the particularly the pectoral, to central, to apical, up into the axilla into supraclavicular lymph nodes
What does the brachial plexus supply?
Is it sensory and motor?
What is the brachial plexus derived from?
What is the pattern of the brachial plexus?
What does brachial mean?
What does plexus mean?
- The brachial plexus is the nervous supply to the upper limb, including all but 1 extrinsic back muscle
- Contains both sensory and motor components?
- The brachial plexus is derived from the anterior rami of C5-C8 and T1
• The pattern of the brachial plexus is:
1) Roots - real
2) Trunks - teenagers
3) Divisions - drinks
4) Cords - cold
5) Nerves/branches – beer
- Brachial – refers to the arm
- Plexus – intricate network or arrangement
What are dermatomes?
What kind of pattern does it have?
What are 3 useful dermatome landmarks in the upper limb?
- Dermatomes are areas of skin innervated by a spinal segment
- Dermatomes have a segmental pattern from embryology
- There is variation and overlap, so its rough determination
• 3 dermatome landmarks in the upper limb:
1) Thumb is C6
2) Middle finger is C7
3) Little finger is C8
How are nerves different from dermatomes supplying the skin?
What supplies the skin?
What do named nerves contain?
- 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
- Named nerves supply the skin
- Named nerves contain afferent neurons from more than 1 spinal level
What are myotomes?
What will the named nerves contain?
What might a named nerve be able to do?
What might one action be represented by?
Why are these actions useful?
- Myotomes are a group of muscles innervated by a single spinal segment, usually with a common action
- Named nerves will contain efferent neurons from multiple spinal level, so named nerve might be able to produce more than 1 action, and 1 action may be represented by more than 1 myotome
- These actions are useful for testing nerve roots
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?
Where does it pass underneath?
What is the plexus bound in?
What does the brachial plexus surround in the axilla?
- The brachial plexus emerges from between the scalenus medius and the scalenus anterior muscles in the root of the neck
- The brachial plexus ten passes underneath the clavicle and out into the axilla
- The plexus is bound in a fascial sheathe in real life
- The brachial plexus raps around the axillary artery in the axilla
Where are the roots of the brachial found?
What structures rap around the front of the brachial plexus?
What structures pass over the top and in between the brachial plexus?
Where is the T1 nerve root located?
What can roots of the brachial plexus be used for?
How is it found?
- The roots of the brachial plexus are found deep in the neck between the scalenus anterior and scalenus medius muscles
- The subclavian artery and clavicle rap around the front of the brachial plexus
- The dorsal scapular and suprascapular pass over the top and in between various parts of the brachial plexus
- The T1 nerve root is located very deep, as it comes out under the T1 vertebrae
- Roots of the brachial plexus can be a regional anaesthesia target
- The brachial plexus is found by looking for the scalene groove between the scalenus anterior and medius (yellow on diagram)
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
