Revision: disorders and injuries of muscles and nerves

Question 1

injury to long thoracic nerve cause and result

Answer 1

cause: as it runs along superficial part of serr ant, it is vulnerable when the limbs are elevated and weapons are a common source of injury eg bullets
result: paralysis of serratus anterior: 1) medial border of scap. moves lat. and post., giving appearance of wing esp when arm is pressed against wall, when arm is raised it is especially prominent as it pulls markedly away from the thoracic wall -> WINGED SCAPULA
2) arm may not be able to be abducted beyond 90 degrees, as the glen. cav. cannot be superiorly rotated

Question 2

cause of an injury to the long thoracic nerve

Answer 2

the course of the nerve runs superficial to the serratus anterior and is especially vulnerable when the upper limb is elevated

therefore it can be damaged by weapons eg bullets

Question 3

result of an injury to the long thoracic nerve

Answer 3

paralysis of serratus anterior: 1) medial border of scap. moves lat. and post., giving appearance of wing esp when arm is pressed against wall, when arm is raised it is especially prominent as it pulls markedly away from the thoracic wall -> WINGED SCAPULA

2) arm may not be able to be abducted beyond 90 degrees, as the glen. cav. cannot be superiorly rotated

Question 4

injury to thoracodorsal nerve cause and result

Answer 4

cause: the nerve runs inferiorly along post. wall of axilla and enters med. surface of lat. dorsi, close to the tendinous part of the muscle
1) surgery in inf. part of axilla
2) mastectomies when the axillary tail of the breast is removed
3) surgery to scapular lymph nodes as the terminal part of the TD lies anterior to them, also the subscapular artery
result: paralysis of the lat. dorsi, leading to the inability to perform activities that require active depression of the scapula (as gravity is usually sufficient):
1) raising the trunk to the arms normally when climbing
2) the use of an axillary crutch, as shoulder is pushed superiorly

Question 5

cause of injury to thoracodorsal nerve

Answer 5

the nerve runs inferiorly to the posteiror wall of the axilla and enters the medial surface of the latissimus dorsi, close to its tendinous part

1) surgery to inferior part of axilla
2) mastectomy, when the axillary tail of the breast is removed
3) surgery to the scapula lymph nodes, as the terminal part of the TD lies anterior to them (also the subscapular artery)

Question 6

result of an injury to thoracodorsal nerve

Answer 6

it leads to the inability to perform activities requiring the active depression of the scapula, as in passive activities gravity is sufficient

1) raising the trunk to the arms when climbing
2) the use of an axillary crutch as the shoulder is pushed superiorly

Question 7

injury to spinal accessory nerve result

Answer 7

loss of motor function of trapezius

marked weakness when elevating/shrugging the shoulders against resistance

Question 8

injury to dorsal scapular nerve result

Answer 8

damage to rhomboids

if one side is paralysed, a sign is that the scapula on the affected side is located farther form the midline than the other

Question 9

injury to axillary nerve cause and result

Answer 9

cause: the nerve passes inf. to humeral head and winds around surgical neck
1) injured during a surgical neck frx therefore
2) dislocation of GHJ
3) compression from incorrect use of crutches

in addition, the deltoid is a common site for intramuscular injections (the axillary nerve runs transversely under deltoid at surgical neck level) so knowledge of its location may prevent damage during surgery

result: 1) atrophy of deltoid -> cannot abduct arm beyond 15 degrees, flattened shoulder appearance -> hollow cavity under acromion
2) loss of sensation over regimental badge area (lateral part of proximal portion of arm)

Question 10

injury axillary nerve cause

Answer 10

the nerve runs inferior to the head of the humerus and winds around the surgical neck

1) therefore, can be injured by a frx to surgical neck
2) dislocation of GHJ
3) compression during inappropriate use of crutches

in addition, as the deltoid is a common site for intramuscular injections, it can be damaged during surgery if its location (transverse path around surgical neck under deltoid) is not precisely known

Question 11

injury to axillary nerve result

Answer 11

1) atrophy of deltoid -> cannot abduct arm beyond 15 degrees, flattened shoulder appearance -> hollow cavity under acromion
2) loss of sensation over regimental badge area, the lateral proximal part of the arm

Question 12

injury to musculocutaneous nerve cause and result

Answer 12

cause: rare occurence in the axilla as it is protected, but can be cut commonly with a weapon eg a knife
result: 1) paralysis of BBC -> weak flexion of arm, weak flexion and supination of forearm (though both are still possible)
2) loss of sensation to lateral surface of forearm by the lateral antebrachial cutaneous nerve

Question 13

injury to radial nerve cause and result

Answer 13

cause: in the arm it can be severed by a mid humeral frx affecting the radial groove. In the 4 arm the deep branch can be severed by deep wounds in the posterior of the 4arm
result: 1) paralysis of triceps (when the radial nerve is damaged by a mid humeral frx, the triceps may only be weakened, but the posterior 4arm muscles are paralysed)
2) paralysis of forearm muscles -> wrist drop - inability to extend hand at wrist and the MCPJs
3) if just the deep branch is severed, it leads to an inability to extend thumb and the 2nd-5th MCPJs
4) small loss of sensation (due to ulnar and median nerve overlap) on the lateral dorsum side of the hand
5) loss of sensation to posterior of arm and forearm

Question 14

cause of injury to radial nerve

Answer 14

1) mid humeral frx across the radial groove
2) deep branch can be damaged by deep posterior forearm cuts

Question 15

result of injury to radial nerve

Answer 15

1) paralysis of triceps brachii (though if damaged at the radial groove it may only be weakened - but the posterior muscles are paralysed still)
2) paralysis of the posterior forearm muscles -> WRIST DROP (inability to extend hand at wrist and the fingers at the MCPJs)
3) if just the deep branch is lacerated, it leads to ina bility to extend MCPJs
4) small loss of sensation to lateral dorsum part of hand due ot overlap by median and ulnar nerve
5) loss of sensation to posteror of arm and forearm

Question 16

Carpal tunnel syndrome cause, result, treatment

Answer 16

cause: anything that increases the size of the nine structures (FPL, FDP, FDS)/their coverings that passes through the carpal tunnel eg through infection, fluid retention, excessive exercise, tenosynovitis, oedema, frxs, dislocations,
- risk factors: occupation involving repetitive tasks, diabetes, RA, hypothyroidism, pregnancy, obesity, menopause
result: median nerve is compressed:
1) loss of coordination and strength in thumb from a loss of movement of thenar muscles
2) para/hypo/anaesthesia in lateral 3.5 digits (not palm as the palamr cutaneous branch rises proximal to the carpal tunnel
3) as condition progresses, sensory problems may radiate into the forearm and axilla
treatment: carpal tunnel incision (partial/complete surgical division of flexor retinaculum) to relieve the pressure on the median nerve

Question 17

Carpal tunnel syndrome result

Answer 17

compression of median nerve:

1) loss of coordination and strength in thumb due to lack of function of thenar muscles
2) loss of sensation to lateral 3.5 digits (not palm as the palmar cutaneous branch of the median nerve rises proximally to CT and does not enter it)
3) as the condition worsens the loss of sensation spreads to forearm and axilla

Question 18

median nerve injury cause and result

Answer 18

cause: 1) compression in carpal tunnel (Carp Tunn Synd)
2) severed in elbow region
3) slashing wrists
result: 1) inability to flex 1st-3rd proximal IPJs and 4th and 5th IPJs are weakoned
2) inability to flex distal 2nd and 3rd IPJs
- > hand of benediction (when the hand attempts to make a fist the index and middle fingers remain partially extended)
- > pinch posture of hand when making an OK sign
- > loss of function of thenar muscles

Question 19

Median nerve injury result

Answer 19

Hand of benediction: paralysis of lateral half of DP and lat. 2 lumbricals

-> no flexion at MCPJs and IPJs of 2nd and 3rd fingers - when asked to make a fist the index and middle fingers remain straight

Also, a pinch posture sign, when an ‘ok’ sign is made the distal IPJ of the index finger hyperextends

Question 20

ulnar nerve injury cause and result

Answer 20

cause: ulnar nerve is vulnerable in several places:
1) posterior to medial epicondyle of humerus (‘funny bone’ if hit on a hard surface)
2) in wrist- Ulnar Canal Syndrome
3) in hand
4) in cubital tunnel formed by tendinous arch connecting the humerus and ulnar heads of the FCU
result: 1) para and anaesthesia to medial 1.5 fingers and hand below
2) wrist flexion causes abduction (as no FCU)
3) MCPJs are hyperextended
4) interosseous muscles atrophy
5) cannot flex 4th and 5th digits at distal IPJs and extend IPJs when attempting to straighten fingers -> CLAW HAND (due to unopposed action of extensors and FDP)

Question 21

ulnar nerve injury cause

Answer 21

vulnerable in several locations: 1) posterior to medial epicondyle of humerus - ‘Funny bone’

2) wrist - Ulnar Canal Syndrome
3) hand
4) in cubital tunnel (formed by the tendinous arches connecting humeral and ulnar heads of FCU)

Question 22

ulner nerve injury result

Answer 22

1) para and anaesthesia to medial 1.5 fingers and corresponding skin of hand below
2) when wrist is flexed abduction is caused (no FCU)
3) MCPJs are hyperextended
4) cannot flex 4th and 5th digits at distal IPJs
5) cannot extend IPJs when attempting to straighten fingers

4 and 5 lead to CLAWED HAND - unopposed action of the FDP and extensors

Question 23

ulnar canal syndrome cause and result

Answer 23

cause: ulnar nerve runs in the ulnar canal, an osseofibrous tunnel formed by the pisohamate ligament in the depression between the hook of hamate and pisiform
result: 1) hypoesthesia in medial hand
2) weakness of intrinsic muscles of the hand
3) clawed hand

Question 24

Ulnar claw vs Hand of benediction

Answer 24

lesion of ulnar nerve at wrist/median nerve at wrist/elbow

appears in long standing cases of nerve damage due to atrophy of interossei/appears when patient attempts to make a fist

little and ring/index and middle fingers affected

medial 2 lumbricals/lat. half of FDP and lat. 2 lumbricals affected most importantly

unopposed extension at MCPJs and flexion at IPJs/inability to flex MCPJs and IPJs of middle and index fingers

Question 25

carpal tunnel syndrome cause

Answer 25

anything that increases the size of the nine structures (FPL, FDP, FDS)/their coverings that passes through the carpal tunnel eg through infection, fluid retention, excessive exercise, tenosynovitis, oedema, frxs, dislocations,

-risk factors: occupation involving repetitive tasks, diabetes, RA, hypothyroidism, pregnancy, obesity, menopause