12.2 Flashcards
At the based of the neck, the roots of the brachial plexus converge forming 3 trunks. Name them.
Superior, middle, inferior trunks
Which trunk is made from the combination of C5 and C6 roots
Superior trunk
Which trunk is the continuation of C7?
Middle trunk
Which trunk is formed from the combination of C8 and T1 roots?
Inferior trunk
Anterior (ventral) nerve division supply which muscles?
Flexors and adductors
Posterior (dorsal) nerves supply which muscles?
Posterior (dorsal) nerves supply the extensors + abductors (muscles)
All 3 posterior division from the trunks combine to form which cord?
Posterior cord
The 2 of the anterior division nerves recombine to form which cord?
Lateral cord
Which cord does the anterior division of the inferior trunk form?
Median nerve
Which nerve innervates: Brachialis, biceps brachii, coracobrachialis muscles?
Musculocutaneous nerve
Which nerve innervates teres minor and the deltoid muscles?
Axillary nerve
Which nerve innervates triceps brachii + extensor muscles in posterior forearm?
Radial nerve
Problems with forearm pronation and supination is due to damage to which myotome?
C6
Problems with arm abduction and lateral rotation is due to damage to which myotome?
C5
Problems with arm adduction and medial rotation is due to damage to which myotomes?
C6,7,8
What are the myotomes associated with elbow flexion?
What are the myotomes associated with elbow extension?
o Flex – C5, C6
o Extend – C7, C8
All intrinsic muscles of the hand are innervated by which myotome (motor fibre of single spinal root)?
T1
Weakness of extensors (hand and forearm) and loss of sensation over dorsal web is indicative of injury to which nerve?
Radial nerve
Inability to extend 4th + 5th digits at interphalangeal joints leading to permanent flexion hence a claw, indicates damage to which nerve?
Ulnar nerve (distally).
The closer to the paw, the worse the claw
Explain ulnar paradox
The ulnar nerve also innervates the ulnar (medial) half of the flexor digitorum profundus muscle (FDP).
If the ulnar nerve lesion occurs more proximally (closer to the elbow), the flexor digitorum profundus muscle may also be denervated.
As a result, flexion of the IP joints is weakened, which reduces the claw-like appearance of the hand. (Instead, the fourth and fifth fingers are simply paralyzed in their fully extended position.)
This is called the “ulnar paradox” because one would normally expect a more proximal and thus debilitating injury to result in a more deformed appearance.
Consequences of a median nerve injury
‘Hand of benediction’ when patient attempts to make a fist.
Inability to oppose thumb.
Proximal median nerve injury –> can’t flex 2nd + 3rd fingers.
Distal median nerve injury –> can’t extend 2nd + 3rd fingers
What is Erb’s palsy?
Upper brachial plexus injury
Brachial plexus is stretched due to tractiontion and C5 tears
Affects:
Ability to abduct the shoulder – arm hangs by side
Arm remains pronated – hand tilted backwards
What is a Klumpke’s paresis?
Lower brachial plexus injury Tears
T1
Affects lower myotomes + dermatomes
Affects:
Paralysis of intrinsic hand muscles – claw hand
Numbness of C8-T1 dermatome
What is downward movement of the scapula called?
Depresion