5. The Brachial Plexus Flashcards
What nervous element forms the roots of the brachial plexus?
Anterior rami C5-T1
Name each of the trunks of the brachial plexus and the nerves that run into them
Superior - C5, C6
Middle - C7
Inferior - C8, T10
Recall the general branching pattern of the brachial plexus
5 roots (C5-T1)
3 trunks (sup, mid, inf)
Each trunk divides into post and ant divisions
Posterior divisions converge to posterior cord
Anterior divisions of sup and mid trunk converge to form lateral cord
Anterior division of inferior trunk –> medial cord
Cords split to form peripheral nerves
What are the main nerves branching from the lateral cord?
Musculocutaneous
Median (via lateral root)
What are the main nerves branching from the posterior cord?
Radial
Axillary
What are the main nerves branching from the medial cord?
Ulnar
Median (via medial root)
Recall the roots that supply the musculocutaneous nerve
C5, C6, C7
Recall the roots that supply the axillary nerve
C5, C6
Recall the roots that supply the ulnar nerve
C8, T1
Recall the roots that supply the median nerve
C6, C7, C8, T1
Recall the roots that supply the radial nerve
All in BP (C5–> T1)
How are the cords named?
With respect to relationship to axillary artery
Recall the branches of the BP that only contain C5 fibres
Dorsal subscapular
Subclavius
Phrenic
Recall the branches of the BP that contain C5 and C6 fibres only
Upper and lower subscapular
Suprascapular
Axillary
Which nerve root fibres contribute to the thoracodorsal nerve?
C7 and C8
Recall the branches of the BP that contain C8 and T1 fibres only
Medial pectoral
Medial brachial cutaneous
Medial antebrachial cutaneous
Ulnar
In general, which nerve root fibres supply the shoulder girdle muscles?
C4-C7
In general, which nerve root fibres supply the shoulder joint and elbow flexor muscles?
C5 + C6
In general, which nerve root fibres supply the elbow joint extensors?
C7 + C8
In general, which nerve root fibres are involved in controlling wrist movement and coarse hand movements?
C6, C7 and C8
Recall the branches of the BP that contain C5,6 and 7 fibres only
Long thoracic
Lat. pectoral
In general, which nerve root fibres are involved in controlling fine hand movements?
C8 - T1
Recall the mnemonic used to remember the organisation of the BP
Reach To Drink Cold Beer
Roots Trunks Divisions Cords Branches
Recall the mnemonic used to remember the main branches of the BP
Most Alcoholics Must Really Urinate: Musculocutaneous Axillary Median Radial Ulnar
Recall the mnemonic used to remember the branches of the posterior cord
ULTRA Upper subscapular Lower subscapular Thoracodorsal Radial Axillary
Recall the mnemonic used to remember the branches of the lateral cord
Must Love Lateral:
Musculotaneous
Lat. pectoral
Lat. median
Recall the mnemonic used to remember the branches of the medial cord
M4U Medial pectoral Medial cutaneous (arm) Medial cutaneous (forearm) Medial branch of median nerve Ulnar
Where does the musculocutaneous nerve run and what is its main function?
Deep in biceps
Flexion and extension
What is the most likely cause of musculocutaneous nerve damage?
Breast cancer surgery
What is the main result of a musculocutaneous nerve injury?
Loss of flexion and supination in forearm
Where does the radial nerve run and what is its main function?
Runs posterior to humerus in radial groove
Motor to posterior arm and forearm
What are the mian consequences of radial nerve injury?
Loss of sensation at anatomical snuff box
Loss of power grip
WRIST DROP
Where does the median nerve run and what is its main function?
Runs through median cubital fossa and carpal tunnel
Supplies wrist, finger flexors, small muscles of thumb and index finger
What are the main consequences of median nerve injury?
Wasting of thenar eminence
Loss of sensation and fine movement in lateral digits
Where does the ulnar nerve run and what is its main function?
Runs posterior to medial epicondyle
Motor to small muscles of hand
What is the main consequence of ulnar nerve injury?
Ulnar claw (due to lumbrical deinnervation) Loss of efficient adduct and abduction in fingers
What is the most common cause of ulnar nerve injury?
Attempted suicide by cutting
Describe the ulnar paradox
Clawing is worse when you injure nerve at wrist than elbow because FDP is also damaged and so flexion of fingers reduced, making appearance seem less clawed
How do you test for ulnar nerve damage?
See LA notes
What is the course of the axillary nerve and what is its main function?
Winds round surgical neck of humerus
Supplies deltoid and teres minor
What is the main consequence of injury to axillary nerve?
Deltoid wasting (loss of shoulder-roundness) Loss of lateral cutaneous nerve sensation
Why is the long thoracic nerve relatively susceptible to damage?
Relatively superficial
What does the long thoracic nerve supply?
Serratus anterior - involved in scapula stabilisation
What is the main consequence of injury to the long thoracic nerve
Winging of scapula
What name is given to the palsy produced if the C5 C6 root is damaged
Erb’s palsy
What is the most common cause of Erb’s palsy?
dystopia or traumatic fall to shoulder
What nerves are most likely to be damaged in Erb’s palsy?
Musculocutaneous
Axillary
Describe the presentation of Erb’s palsy
Loss of sensation in regimental patch
Atrophy of biceps, brachialis and deltoid
“Waiter’s tip”
What name is given to the palsy produced if the C8 T1 root is damaged
Klumpke’s palsy
What nerves are most likely to be damaged in Klumpke’s palsy?
Median
Ulnar
Describe the presentation of Klumpke’s palsy?
Clawed hand
What is the most common cause of Klumpke’s palsy?
Abnormal birth
Which muscles are affected by a Klumpke’s palsy?
Intrinsic muscles of hand, wrist and finger flexors and forearm pronators
