Flashcards in Nerve injuries and consequences in the upper limb Deck (47)
Draw the brachial plexus.
Remember: proximal to distal on the posterior branch = upper subscapular thoracodorsal lower subscapular
Proximal to distal on the medial branch = medial pectoral medial cutaneous nerve of the ARM medial cutaneous nerve of the FOREARM
Name the supraclavicular branches of the brachial plexus and state which muscles they innervate.
Dorsal scapular nerve – rhomboids + levator scapulae (+C34)
Long-thoracic nerve - serratus anterior
Supraclavicular nerve – supraspinatus + infraspinatus
Subclavian nerve - subclavius
Name the infraclavicular branches of the brachial plexus and state the muscles that they innervate.
Lateral pectoral nerve – pectoralis major
Thoracodorsal nerve – latissimus dorsi
Upper subscapular nerve – subscapularis (and the lower subscapular nerve)
Lower subscapular nerve – teres major
Medial pectoral nerve – pectoralis minor and pectoralis major
Medial cutaneous nerve of the arm – sensory to medial part of the arm
Medial cutaneous nerve of the forearm – sensory to medial part of forearm
Name the terminal branches of the brachial plexus and state the muscles that they innervate.
Musculocutaneous – anterior compartment of arm
Axillary – deltoid + teres minor
Radial – posterior compartment of arm and forearm
Median – most anterior forearm muscles + thenar muscles + lumbricals 1+2
Ulnar – flexor carpi ulnaris + ulnar half of flexor digitorum profundus + all intrinsic hand muscles (except those innervated by the median)
The cords of the brachial plexus are named because of their position relative to what important structure?
Which spinal nerves make up each of the following nerves:
Dorsal Scapular- C5
Long Thoracic- C567
Suprascapular - C56 (+C4)
Subclavian - C56 (+C4)
Lateral Pectoral- C567
Medial Pectoral- C8T1
Upper Subscapular- C56
Lower Subscapular- C56, C678
Which two muscles, which start outside the hand, does the ulnar nerve innervate?
Flexor carpi ulnaris (FCU)
Ulnar half of flexor digitorum profundus (FDP)
Which nerves supply the shoulder girdle muscles?
Which nerves supply the shoulder muscles and elbow joint flexors?
Which nerves supply the elbow extensors?
Which nerves are responsible for coarse wrist and hand movements?
Which nerves supply small muscles of the hand (fine movements)?
Describe the dermatome pattern of the skin on the posterior of the upper limb?
They are in strips going from C6-C8 from top to bottom
Describe the dermatome pattern of the skin on the anterior of the upper limb?
Same as the posterior side but there are dermatomes of C5 and T1 running down the middle with their apex at the wrist
Why is the dermatome pattern different to the cutaneous nerve pattern?
A dermatome is the area of skin innervated by a single spinal nerve
A cutaneous nerve pattern is the area of skin innervated by a peripheral nerve
As the peripheral nerves contain various spinal nerve root fibres, the cutaneous nerve pattern is very patchy compared to the dermatome pattern.
What is the benefit of having a brachial plexus instead of having spinal nerves directly innervating the upper limb muscles?
If a muscle group is innervated by one nerve root, damage to that nerve root will cause total loss of function of the muscle. If it is innervated by more than one nerve root then there may still be some function.
What does the axillary nerve supply and what branch of the axillary nerve is responsible for sensory innervation of the skin of the regimental badge area?
Deltoid + teres minor
Superior lateral cutaneous branch
How is the axillary nerve commonly damaged?
What are the consequences of axillary nerve damage?
Loss of function of deltoid
Anaesthesia or parasthesia of the regimental badge area
How can you check to see whether the axillary nerve has been damaged in a shoulder dislocation?
Check for anaesthesia or parasthesia in the regimental badge area
Describe the passage of the radial nerve through the arm.
Exits the axilla posterior to the axillary artery
Passes posterior to the humerus in the radial groove, with the deep brachial artery between the medial and lateral heads of triceps
Perforates the lateral intermuscular septum
Enters the cubital fossa
Divides into superficial radial nerve (sensory) and posterior interosseous nerve (motor)
How is the radial nerve commonly damaged?
Fractures of the humerus – because the radial nerve is closely associated with the humerus in the radial groove
What are the consequences of radial nerve damage?
Anaesthesia of the dorsal palm (on the thumb side)
Wasting of posterior compartment muscles of arm and forearm
What is the most important outcome in radial nerve injury and how does it happen?
Loss of the power grip
To accommodate for extension, the flexors of the fingers are slightly longer than they need to be.
So extension of the wrist allows shortening of the flexors to maximise their efficiency and allow the power grip
With radial nerve palsy, you can’t extend the wrist anymore so you can’t perform the power grip
Describe the passage of the musculocutaneous nerve down the arm.
Exits axilla by piercing coracobrachialis
Descends between biceps brachii and brachialis, supplying both
Continues as the lateral cutaneous nerve of the forearm
When can the musculocutaneous nerve be damaged?
It isn’t often damaged by trauma because it is well protected by the anterior compartment muscles
It can be cut during surgery for breast cancer
Describe the passage of the ulnar nerve down the arm.
Descends in the medial arm
Passes posterior to the medial epicondyle
Descends down the ulnar aspect of the forearm to the hand
What are two common sites of damage of the ulnar nerve?
Injury to the medial epicondyle of the humerus
Injury to the wrist
What situation commonly encountered by clinicians could cause injury at the wrist?
Self-harm and attempted suicide