nerves

Question 1

what spinal segments do the upper limb and its limb girdle get sensory and motor nerve supplies from

Answer 1

C4-T1

Question 2

what do spinal segments C3 to C7 give muscle movement supply to

Answer 2

shoulder girdle

Question 3

what do spinal segments C5 and C6 give muscle movement supply to

Answer 3

shoulder joint and elbow flexors

Question 4

what do spinal segments C7 and C8 give muscle movement supply to

Answer 4

elbow joint extensors

Question 5

what do spinal segments C6 to C8 give muscle movement supply to

Answer 5

wrist musles and coarse hand muscles

Question 6

what do spinal segments C8 and T1 give muscle movement supply to

Answer 6

fingers and thumb (small muscles of hand for fine movements)

Question 7

what does the axillary nerve supply

Answer 7

winds round neck of humerus to supply C5 and C6 fibres to deltoid (main abductor of shoulder)

Question 8

when can the axillary nerve be injured, and consequences

Answer 8

shoulder dislocations (travels under shoulder joint) and upper humeral fractures (e.g. surgical neck), resulting in loss of abduction and eventual wasting of deltoid and teres minor, as well as loss of sensory innervation to superolateral shoulder skin (innervated by superior lateral cutaneous nerve of arm, from axillary nerve)

Question 9

where does radial nerve wind in arm

Answer 9

winds posterior to humerus in radial groove between attachements of medial and lateral bicep heads

Question 10

what radial nerve fibres can be damaged by fractures of mid-humeral shaft (runs in radial groove), and what can this lead to

Answer 10

C7-T1 fibres, leading to loss of function of extensor muscles in forearm, causing muscle wastage (if happens high in limb), wrist drop and weakness of power grip (extension of wrist required, so flexor muscles work harder but can’t fully compensate)

Question 11

where do radial nerve sensory losses by fractures of mid-humeral shaft affect

Answer 11

variable area on posterior surface of thumb and lateral dorsal hand (substantial overlap with other nerves)

Question 12

what muscles do lateral and medial cords supply

Answer 12

only flexor muscles

Question 13

what fibres are contained within lateral cord, and hence which muscle compartments is it principally concerned with

Answer 13

C5-C7, so muscles acting on shoulder and elbow

Question 14

most important branch of lateral cord, and what does it supply

Answer 14

musculocutaneous branch, supplying elbow flexors (biceps brachii and brachialis), with biceps brachii also being the key muscle in supination

Question 15

when may the musculocutaneous nerve be damaged

Answer 15

during breast cancer surgery for removal of lymph nodes (not trauma as well protected by muscles)

Question 16

what fibres are contained within medial cord, and hence which muscle compartments is it principally concerned with

Answer 16

C8-T1, so muscles acting in forearm and hand

Question 17

main branch of medial cord

Answer 17

ulnar nerve

Question 18

what does the ulnar nerve supply

Answer 18

most intrinsic muscles in hand

Question 19

what and where is the ulnar nerve most vulnerable to

Answer 19

compression, cuts and fractures where is passes posterior to medial epicondyle of humerus at elbow, self harm to wrist

Question 20

consequences of ulnar nerve damage

Answer 20

weakness and wasting of many small muscles in hand (less serious than expected as really vital small muscles of hand, controlling fine movements of thumb and index finger, are served by median nerve), as well as loss of sensation to lateral half of ring finger, and little finger

Question 21

why might clawing be seen in ulnar nerve damage, and why is distal damage more severe than proximal damage

Answer 21

loss of lumbrical contraction means loss of flexion of metacarpophalangeal joins and weakened extension of interphalangeal joints, causing unopposed activity of long muscles of fingers lying in forearm, also affecting PAD and DAB; more severe if injury at wrist (distal) than at elbow (proximal), as it innervates ulnar half of flexor digitorum profundus, so flexion of interphalangeal joints is weakened, so is less claw-like

Question 22

where is sensory loss in median nerve injuries present

Answer 22

along medial part of hand, and medial (usually 1.5) fingers

Question 23

what nerve do lateral and medial cords both contribute to formation of

Answer 23

median nerve

Question 24

what fibres does the median nerve acquire from brachial plexus

Answer 24

C6-T1

Question 25

what does median nerve supply (motor)

Answer 25

most of wrist and finger flexors in forearm, and most small muscles of thumb and index finger

Question 26

what does median nerve supply (sensory)

Answer 26

lateral part of palmar hand

Question 27

what sorts of activities does injury or entrapment of median nerve make impossible, and why

Answer 27

delicate hand activities e.g. writing, as wasting of lateral lumbricals and thenar eminence (except adductor pollicis, as supplied by ulnar nerve)

Question 28

when does the median nerve often become entrapped

Answer 28

as it passes through carpal tunnel (carpal tunnel syndrome)

Question 29

what spinal segment causes flexion of shoulder

Answer 29

C5

Question 30

what spinal segments cause extension of shoulder

Answer 30

C6,7,8

Question 31

what spinal segments cause flexion of elbow

Answer 31

C5,6

Question 32

what spinal segments cause extension of elbow

Answer 32

C7,8

Question 33

what spinal segments cause pronation of wrist

Answer 33

C7,8

Question 34

what spinal segment causes supination of wrist

Answer 34

C6

Question 35

what spinal segments cause flexion/extension of wrist

Answer 35

C6,7

Question 36

what spinal segment causes abduction/adduction of digits in hand

Answer 36

C7

Question 37

what spinal segments cause flexion/extension of fingers

Answer 37

C7,8

Question 38

why isn’t sensory innervation (cutaneous nerve patterns( the same as dermatome innervation

Answer 38

nerve fibres supplying dermatomes might come from more than one peripheral nerve, due to recombination in plexus

Question 39

what fibres form the long thoracic nerve

Answer 39

roots of C5,6,7

Question 40

what muscle is affected by damage to long thoracic nerve

Answer 40

serratus anterior (long thoracic nerve is relatively superficial, so easily damaged)

Question 41

main function of serratus anterior, and hence consequence if long thoracic nerve is damaged

Answer 41

holds down surface of scapula, so pressing against a wall will lead to winging of the scapula

Question 42

what is the name of injuries to upper roots

Answer 42

Erb-Duchenne Palsy

Question 43

when do injuries to upper roots occur, and what roots are commonly affected

Answer 43

stretch neck relative to shoulder, so especially affects C5 and C6 (trauma, childbirth)

Question 44

what is the commmon presentation caused by injuries to upper roots

Answer 44

“Waiter’s Tip”, where many muscles in shoulder and arm are affected, with the forearm pronated by lack of biceps supination

Question 45

what is the name of injuries to lower roots

Answer 45

Klumpke’s Palsy

Question 46

common cause of injuries to lower roots, and what roots are commonly affected

Answer 46

over-abduction due to gripping overhead to break a fall, or at birth,, so overextends T1 (and sometimes C8)

Question 47

what is the common presentation caused by injuries to lower roots

Answer 47

loss of activity to small muscles of hand (T1) via ulnar and median nerves results in clawed hand (wrist and finger flexors e.g. flexor carpi ulnaris, ulnar part of flexor digitorum profundus, are damaged, with extensors unopposed)