Nerve Lesions, Injuries

Question 1

lesion of long thoracic nerve

Answer 1

• Lesion –> paralysis of serratus anterior muscle –> loss of scapular protraction –> winged scapula
  
  • ​The serratus anterior is a protractor of the scapula
• Runs with lateral thoracic artery - could also lose blood supply to serratus anterior
• The long thoracic nerve in that it innervates its target muscle from the superficial aspect of the muscle. (Most muscles are innervated from their deep surface, as this provides protection for the nerve.) Given its superficial position, the long thoracic nerve may be lesioned during surgeries taking place in the axilla (classically, a radical mastectomy), which results in paralysis of the serratus anterior muscle.
  
  • The patient may complain of difficulty combing the hair, placing an object on a shelf, and other activities that require protraction.
  • When a posteriorly directed force is placed on the scapula (such as leaning on a wall using an outstretched hand), the serratus anterior cannot contract to hold the scapula on the posterior chest wall, so the scapula begins to protrude through the skin of the posterior chest wall (a “winged scapula”).

Question 2

Compression or lesion of median nerve at the carpal tunnel

• what muscles does the median nerve innervate in the hand?
• motor findings, if severe enough?

Answer 2

• Carpal tunnel syndrome may arise from compression of the median nerve as it passes through the narrow carpal tunnel in the wrist.
• This compression can cause numbness, tingling, burning sensations, or pain in the dermatome of the median nerve – specifically, in the fingers
  
  • It generally does not involve the palm because the superficial palmar branch of the median nerve actually branches proximal to the point where it enters the carpal tunnel
• Innervates the thenar muscles (OAF) and lumbricals to index and middle finger
  
  • Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis all get recurrent branch
• if severe –> ape thumb
  
  • inability to oppose the thumb bc we’ve lost opponens pollicis
  • (the longus versions of the other muscles are just fine)

Question 3

What causes carpal tunnel?

common causes?

Answer 3

• compression of median nerve as it passes through the narrow carpal tunnel in the wrist
• This compression can cause numbness, tingling, burning sensations, or pain in the dermatome of the median nerve – specifically, in the lateral 3.5 digits
  
  • It generally does not involve the palm because the superficial palmar branch of the median nerve actually branches proximal to the point where it enters the carpal tunnel
• common causes
  
  • Overuse/inflammation of flexor tendons
  • Dislocation of lunate
  • Obesity
  • Pregnancy

Question 4

why isn’t the palm involved in carpal tunnel?

Answer 4

• Superficial palmar branch does not pass

through carpal tunnel, goes above

Question 5

lesion to recurrent branch of median nerve

(caused by laceration)

Answer 5

• ape thumb - inability to oppose thumb
• no sensory findings, since that’s just a motor branch to the thenar eminence

Question 6

What happens when you hit your funny bone?

Answer 6

• Hitting the “funny bone” refers to transient trauma of the ulnar nerve as it passes under the medial epicondyle of the humerus
  
  • ​passes throuch cubital tunnel (groove between olecranon and medial epicondyle)
• Notice that it’s only the medial half of the ring finger that gets the “pins and needles” sensation, not the lateral half.
  
  • Dermatome for ulnar nerve is the medial one and a half digits (pinkie and half of ring finger)

Question 7

name the arteries that run with these nerves of the brachial plexus:

axillary nerve –>

radial nerve –>

long thoracic nerve –>

Answer 7

• There are a few notable examples of arteries that run with nerves of the brachial plexus. A fracture that lesions a given nerve may easily also lesion the artery that travels with it.
• Axillary nerve –> posterior circumflex humeral artery (through the quadrangular space)
• Radial nerve –> deep (profunda) brachial artery (runs in the spiral groove)
• Long thoracic nerve –> lateral thoracic artery

Question 8

midshaft humerus fracture:

what happens?

(fracture at #22)

Answer 8

• Radial nerve damaged, as it runs through spiral groove
• Deep (profunda) brachial artery damaged
• The radial nerve is the major source of innervation for the posterior arm and posterior forearm. These muscles are predominantly extensors (in fact, all muscles of the upper limb with extensor in their names are innervated by the radial nerve). One of the most prominent motor findings of a radial neuropathy is a wrist drop, in which the hand cannot be extended at the wrist.
• loss of cutaneous sensation @ posterior forearm and lateral side dorsum of hand
• Can’t extend at all these joints, bc radial nerve innervates all these muscles:
  • Extension at the wrist - extensor carpi radialis longus and brevis, and extensor carpi ulnaris
  • Extension at the metacarpophalangeal joints - extensor digitorum, extensor indicis, and extensor digiti minimi
  • Extension at the interphalangeal joint of the thumb - extensor pollicis longus

Question 9

proximal humerus fracture, at surgical neck

Answer 9

• the quadrangular space is right next to the surgical neck of the humerus
• Would damage the axillary nerve and posterior circumflex humeral artery (more rare though)
• Axillary nerve could also be damaged by shoulder dislocation

(A proximal humerus fracture is a break in the upper part of your humerus near your shoulder - surgical neck. A mid-shaft humerus fracture is a break in the middle of your humerus - sprial groove. Distal humerus fractures occur near your elbow - supracondylar.)

Question 10

distal humerus fracture

aka supracondylar fracture

• lesion to what nerve?
• clinical presentation
• what muscle could impinge on same nerve?

Answer 10

• occurs just above elbow
• lesion to median nerve
• now in addition to carpal tunnel syndrome, we also have most of the anterior forearm (flexors/pronators) affected
  
  • Hand of Benediction when asked to make a fist
  • weakness flexing the hand at the wrist as well as weakness flexing at most of the interphalangeal joints
    • ​AIN damaged can’t make OK sign
  • Pronation would also be lost, as both pronators are innervated by the median nerve

instead of fracture, this could be due to prontator teres impingement:

• median nerve runs through the pronator teres. Could be squeezed by overuse of pronator teres
• only difference from fracture is that pronator teres is working

Question 11

Answer 11

The spiral groove of the humerus transmits the radial nerve and its accompanying artery, the profunda (deep) brachial artery. Can be damaged in midshaft humeral fracture.

(A)The axillary nerve runs through the quadrangular space and may be lesioned with a much more proximal humeral fracture or a shoulder dislocation.

(B)The axillary artery is much more proximal than the spiral groove.

(C)The lateral thoracic nerve is usually lesioned by surgeries in the axilla that may get close to the superficial surface of the serratus anterior muscle (such as a radical mastectomy); a humeral fracture is unlikely to lesion this nerve.

(D)Like the axillary nerve, the posterior circumflex humeral artery runs through the quadrangular space and may be lesioned by similar injuries.

(E)(correct answer)

Question 12

Saturday night palsy

• what nerve is affected?
• what is another action that compresses the nerve
• presentation

Answer 12

• More proximally than a midshaft humerus fracture, the radial nerve may be lesioned proximally, in the axilla by compression.
• “Saturday night palsy,” - falls asleep with some hard surface lodged in the axilla (think of falling asleep with one’s arm over the back of a chair).
• This may be seen in patients using crutches.
• Or if you’re the big spoon!
• since this is a more proximal lesions, weakness of the triceps brachii might also be seen in addition to the wrist drop.
  
  • Loss of triceps (extends the forearm)
• Can’t extend at all these joints, bc radial nerve innervates all these muscles:
  
  • Extension at the elbow - triceps brachii
  • Extension at the wrist - extensor carpi radialis longus and brevis, and extensor carpi ulnaris
  • Extension at the metacarpophalangeal joints - extensor digitorum, extensor indicis, and extensor digiti minimi
  • Extension at the interphalangeal joint of the thumb - extensor pollicis longus

Question 13

What humeral fracture may cause an axillary neuropathy?

What blood vessel may also be lesioned?

Answer 13

• Surgical neck fracture
  
  • lesions axillary nerve and posterior circumflex humeral artery
  • as they pass through quadrangular space

Question 14

shoulder dislocation

would damage what nerve and artery?

Answer 14

• Should dislocation is proximal, so could damage axillary nerve, which runs through quadrangular space with posterior circumflex humeral artery
• usually dislocates anteriorly and inferiorly

Question 15

What are the four fractures of the humerus,

match them with their main nerve lesion,

and artery if applicable.

Answer 15

• proximal humerus fracture @ surgical neck
  
  • axillary nerve and posterior circumflex humeral artery
• mid-shaft humerus fracture @ sprial groove
  
  • radial nerve and profunda brachial artery
• distal humerus fractures @ supracondyle
  
  • median nerve including AIN
• distal humerus fracture @ medial epicondyle
  
  • ulnar nerve

Question 16

name a major clinical finding for each of these 4 fractures to the humerus:

Answer 16

• surgical neck - axillary nerve + posterior circumflex humeral
  
  • inability to ABduct beyond 15^o
• midshaft - radial nerve + profunda brachial artery
  
  • wrist drop
• supracondylar - median nerve
  
  • ape thumb (as with carpal tunnel)
  • hand of benediction (can’t make fist)
  • if AIN can’t make OK sign
• medial epicondylar - ulnar nerve
  
  • tingling in pinkie and half of ring finger, radial deviation of wrist upon flexion, weakness of adduction and abduction of fingers

Question 17

What do we need to stand on toes?

Answer 17

• Need tibial nerve, which provides plantar flexion
• Plantaris, Gastrocnemius, Soleus = major plantar flexors
• Tibialis posterior, flexor digitorum longus, flexor hallucis longus also help with plantar flexion, and some inversion of foot

Question 18

What do we need to stand on heels?

Answer 18

• Need dorsiflexion, from common fibular (peroneal) nerve

Question 19

What could result from a fracture through the femoral neck?

Answer 19

• Damage to the medial circumflex femoral artery –> necrosis of femoral head
  
  • The medial passes up the neck of the femur to serve as a blood supply of the femoral head.
  • A fracture through the femoral neck may cause a loss of blood supply to the femoral head and associated avascular necrosis.
  • (Anastomoses with the lateral circumflex femoral artery. They’re branches off the profunda, which is a branch off the femoral.)

Question 20

Herniation of a loop of bowel under the inguinal ligament would put which nerve at risk for damage?

Answer 20

The femoral nerve

• This question stem describes a femoral hernia (bowel herniates under the inguinal ligament and into the superior thigh).
• The femoral nerve runs through this space, and so would be most at risk.

Question 21

A patient presents with a proximal fibular fracture; a lesion of a nearby nerve is suspected.

Which movements is most likely to be affected by this patient on physical examination?

Answer 21

Dorsiflexion of the foot at the ankle.

Possibly also eversion of the foot.

• Dorsiflexion is accomplished by the anterior compartment of the leg, which is innervated by the deep fibular nerve.
  
  • It is the common fibular nerve that passes over the neck of the fibula, and then splits to form the superficial and deep fibular nerves (both of which may be affected in this case).
    
    • The superficial fibular nerve supplies the fibularis longus and brevis, form the lateral compartment of the lower leg. They act to evert the foot.

Question 22

If your knees are locked, what’s the problem?

Answer 22

• Unlocking of the knee is the role of the popliteus muscle
• Innervated by the tibial nerve (posterior compartment of the leg).

Question 23

Answer 23

• The medial circumflex femoral artery runs up the femoral neck (which is fractured in this x-ray) and may be lesioned in a femoral neck fracture.
• This puts the femoral head at risk for avascular necrosis.

Question 24

What causes foot drop?

Answer 24

• Damage to fibular/peroneal nerve
• Can’t dorsiflex

Question 25

Why might a patient’s foot be dragging?

You see patient leaning when walking.

When the patient lift his left foot, the left hip tilts downward.

“Waddling gate” “Trendenlenberg sign”

Answer 25

• There’s a problem with the gluteus medius and gluteus minimus
  
  • Most important function actions of gluteus medius and minimus is to abduct the trunk and keep the pelvis level when the lower limb is off the ground.
  • Muscles on opposite side of lifted food contract to level the pelvis
• The superior gluteal nerve innervates gluteus medius, the gluteus minimus and the tensor fasciae latae muscle
• So it could either be d/t injury of superior gluteal nerve, or injury of gluteus medius/minimus, or hip joint injury
• Since the left hip is dipping, injured nerve is on the right side

Question 26

Which muscles do we use when walking,

to extend the thigh at the hip?

(Thigh goes backwards)

Answer 26

• Hamstrings
• (Use gluteus maximus as extensor when running, jumping up from seated position, climbing stairs)

Question 27

Why do the hamstrings take longer to heal?

Answer 27

• They have a lousy blood supply, not direct
  
  • The posterior thigh is supplied by perforating branches of the deep femoral artery (small)

Question 28

What’s common for ppl with osteoporosis?

Answer 28

• Osteoporosis weakens the neck of the femur, can lead to fracture
• Femoral neck fracture –> avascular necrosis of femoral head –> need hip replacement
  
  • Common
  • Because the branches of the medial circumflex femoral artery had to cross the neck of the femur to get to the head of the femur, and there’s limited collateral blood supply

Question 29

What’s the most clinically significant nerve of the hand?

Answer 29

• The recurrent branch of the median nerve
• Prone to injury: unlike most muscle innervation, the recurrent branch of the median nerve is superficial.
  
  • Hand surgeons have to be careful when relieving carpal tunnel, not to nick this nerve
• Without it, no power grip

Question 30

Why is the recurrent branch of the median nerve clinically significant?

“million dollar nerve”

Answer 30

• It’s the only nerve that goes through the carpal tunnel (along with nine tendons)
• After it crosses the carpal tunnel, it gives rise to the recurrent branch of the median nerve innervates the three thenar eminence muscles
  
  • Problem: unlike most muscle innervation, the recurrent branch of the median nerve is superficial. Prone to injury.
  • “million dollar nerve”

Question 31

anatomic snuffbox

what might fracture there?

Answer 31

• In the anatomical snuffbox, the scaphoid and the radius articulate to form part of the wrist joint. In the event of a blow to the wrist (e.g falling on an outstretched hand), the scaphoid takes most of the force.
• If localised pain is reported in the anatomical snuffbox, a fracture of the scaphoid is the most likely cause.
• A fracture of the scaphoid can disrupt the blood supply to the proximal portion – emergency. Failure to revascularise the scaphoid can lead to avascular necrosis, and arthritis

Question 32

wrist drop

Answer 32

• radial nerve
• inability to extend the hand at the wrist, because all the wrist extensors are innervated by radial nerve
• Can happen in children when arm is yanked, their annular ligament hasn’t fully formed yet –> dislocation of humerus –> lesion to radial nerve

Question 33

hand of benediction

• cause
• clinical presentation

Answer 33

• Median n. palsy at (elbow or higher) results in lag of radial 3 digits in flexion due to extrinsic muscle weakness
• “Hand of Benediction” is the clinical sign of a proximal median neuropathy - could be caused by supracondylar fracture leading to lesion of median nerve
  • when attempt to make a fist
  • absence of flexion and extension of digits 2 + 3 (at least at the interphalangeal joints)
• also have an ape thumb (inability to oppose the thumb) due to weakness of the thenar eminence muscles (same as carpal tunnel)

Question 34

claw hands

Answer 34

• median claw
  
  • Hand of benediction - upon trying to form fist, digits 1-3 remain extended
  • bc flexor digitorum profundus half innervated by median/ulnar
  • also without median nerve, knock out thenar eminence
• ulnar claw when attempt to extend fingers
  
  • Claw hand / ape hand occurs due to an ulnar nerve injury, usually a distal lesion.
  • The fourth and fifth digits are flexed and the patient cannot straighten these two fingers.
  • The 4th and 5th digits (without lumbrical function) assume a “claw” appearance, with hyperextension at the MCPs and flexion at the IP joints.
  • bc extensor digitorum (innervated by PIN branch of radial) only extends strongly at MCP joints. PIP and DIP require lumbricals, which are also half ulnar/half median innervated
  • ulnar nerve also innervates hypothenar eminence

Question 35

ape hand

Answer 35

• lesion to recurrent branch of median nerve
• no OAF, so no opposable thumb

Question 36

What happens when there is a severe lesion of median nerve or ulnar nerve?

Answer 36

• Different degrees of digital clawing:
  
  • Median claw hand
  • or Ulnar claw hand
• Patient will have difficulty extending fingers at IP joints
  
  • bc the extensor digitorum (innervated by PIN branch of radial) only extends strongly at MCP joints.
  • extension of PIP and DIP require lumbricals, which are half ulnar/half median innervated
• Difficulty flexing hand at both IP joints
  
  • Because flexor digitorum profundus is half innervated by median/ulnar

Question 37

What nerves might be stretched when you dislocate head of humerus?

Answer 37

• Either the axillary nerve or the radial nerve
  
  • More the axillary than the radial
• Because they’re situated near the surgical neck or the midshaft portion of the humerus, when it’s dislocated anteriorly and inferiorly.

Question 38

What nerve lesion could happen when yanking a child’s arm?

Answer 38

• Because children have weak annular ligament, there can be subluxation/dislocation of radial head
• Distal lesion stretches the deep branch of radial nerve
  
  • Subluxation (partial dislocation) of radial head
  • Wrist drop - inability to extend hand at wrist bc all the wrist extensors are innervated by radial nerve
  • weak

Question 39

carpal bones

Which are the most clinically significant?

Answer 39

• 2 rows of 4 each
• Most important are the lunate and schaphoid, because they articulate with the more massive bone at the wrist, the distal radius
  
  • Lunate and schaphoid are at risk of trauma after FOOSH
  • Note that the radius is the larger of the two wrist articulations (whereas at the elbow, the ulnar was the larger)
• 3rd most clinically significant is the hamate - with FOOSH, may fracture the hook of the hamate –> lesion of the ulnar nerve –> effect on intrinsic hand muscles
• Some Lovers Try Positions That They Cannot Handle (or go in circle: So Long The Pinkie Here Comes The Thumb)

Question 40

most commonly fractured carpal bone?

2nd most commonly fractured?

Answer 40

• 1st: scaphoid
• 2nd: hook of hamate

Question 41

Which wrist bones may be affected after Fall On Outstretched Hand?

What could happen?

Answer 41

• Fracture of scaphoid or dislocation of lunate
  
  • the bigger bones that articulate with the radius
• The scaphoid bone is the most frequently fractured of the carpal bones –> avascular necosis of proximal part of scaphoid –> tenderness in anatomic snuffbox
• Otherwise, lunate dislocated, anteriorly into the carpal tunnel –> cause of latent carpal tunnel syndrome

Question 42

cause of latent carpal tunnel?

Answer 42

• can occur after FOOSH –> lunate carpal bone displaced anteriorly into carpal tunnel
• median nerve compression

Question 43

Which nerve is damaged by a fracture of the hook of the hamate?

(After FOOSH)

Answer 43

• ulnar nerve
  
  • runs through Guyon’s canal
  • could have tingling in pinkie and half of ring finger (palmar and dorsal sides)

Question 44

can’t finger spread or bring fingers back -

what nerve has been lesioned?

Answer 44

• ulnar nerve gives ability to finger spread
  
  • innervates all the interosseous muscles (and the adductor pollicis)
• PAD-DAB innervated by deep branch of ulnar nerve
  
  • Palmar interosseous muscles ADduct
  • Dorsal interosseous muscles ABduct
• whereas thumb
  
  • extension: radial (deep branch)
  • flexion: AIN of median nerve, Recurrent of median nerve

Question 45

what can’t the thumb do if…

• Radial nerve is lesioned
• Median nerve is lesioned
• Ulnar nerve is lesioned

Answer 45

• Radial - ABduction, extension (all the PIN)
• Median - ABduction, flexion, opposition (recurrent branch, AIN for flexion)
• Ulnar - ADduction

Question 46

what is the terrible triad for lateral knee injuries?

Answer 46

Torn:

• ACL
• tibial/medial collateral ligament
• medial meniscus

Question 47

What nerve can be lesioned by lateral trauma just distal to the knee joint?

Answer 47

• common fibular nerve, sweeps around the fibular neck
  
  • in a subcutaneous, vulnerable position
• so lateral trauma just distal to the knee joint –> traumatizes the common fibular ligament –> numbness, tingling, pain
  
  • If serious affects the superficial/deep fibular nerves which innervate lateral/anterior leg

Question 48

Answer 48

The answer is (D).

The dorsal scapular nerve innervates the rhomboid major and minor muscles, and the levator scapulae. These are all retractors of the scapula.

(A)The deltoid and supraspinatus are the main abductors of the humerus at the glenohumeral joint. They are innervated by the axillary and suprascapular nerves, respectively.

(B)The main medial rotator of the humerus at the glenohumeral joint is the subscapularis, innervated by the upper and lower subscapular nerves. The latissimus dorsi and teres major, innervated by the thoracodorsal and lower subscapular nerves, respectively, also assist with medial rotation.

(C)The main depressors of the scapula are the lower fibers of the trapezius, innervated by the (spinal) accessory nerve, and the pectoralis minor, innervated by the medial pectoral nerve. The latissimus dorsi also contributes.

(D)Vertebral column extension is accomplished by the erector spinae and transversospinalis muscles, which are innervated by dorsal rami (similar name, but not the same thing).

Question 49

brachial plexus injuries:

Damages to C5, C6, C7, C8, T1 affect what?

Answer 49

C5 – Shoulder abduction, extension, and external rotation, and some elbow flexion.

C6 – Elbow flexion, forearm pronation and supination, some wrist extension.

C7 – Diffuse loss of function in the extremity without complete paralysis of a specific muscle group, elbow extension

C8 – Finger extensors, finger flexors, wrist flexors, hand intrinsics

T1 – Hand intrinsics

Question 50

proximal median nerve lesion

Answer 50

• all pronation ability would be lost
  
  • bc the two pronators (pronator teres and pronator quadratus) are innervated by median nerve
    
    • AIN of median nerve to pronator quadratus
    • Median nerve to pronator teres

Question 51

lesion of Anterior Interosseous Nerve

• what is it a branch of?
• what does it innervate?
• clinical sign?

Answer 51

• AIN is a branch of the median nerve
• AIN innervates 3 deep muscles of anterior forearm:
  
  • flexor digitorum profundus (to digits 2,3)
  • flexor pollicis longus
  • pronator quadratus (but pronator teres is still fine, median nerve)
• Clinical: someone with AIN palsy can’t make OK sign!
  
  • can’t flex index finger at DIP
  • can’t flex thumb IP

Question 52

2 pronators of the arm

Answer 52

• Pronation and supination occur at the proximal and distal radioulnar joints.
• pronator teres and pronator quadratus
• Both innervated by the median nerve
  
  • proximal median nerve lesion: all pronation ability would be lost.

Question 53

2 supinators of the arm

Answer 53

• Pronation and supination occur at the proximal and distal radioulnar joints.
• biceps brachii
  
  • ​musculocutaneous nerve
• the supinator
  
  • ​radial nerve

Question 54

wrist:

• which bone articulates more with the wrist joint?
• most frequently fractured bone of wrist?
• most frequently dislocated?
• second most frequently fractured?

Answer 54

• radius at wrist
  
  • so injuries from FOOSH occur between carpal bones in contact with the radius
• scaphoid = most fractured
• lunate = dislocated, usually anteriorly
• hamate = second most frequently fractured
  
  • usually it is the “hook” of the hamate that is fractured from its anterior surface.

Question 55

A midshaft fracture of the humerus

leads to lesion of radial nerve.

What actions are compromised?

Answer 55

• wrist extension
  
  • the extensor carpi radialis longus and brevis, and extensor carpi ulnaris are innervated by the radial nerve.
• supination of the radius at radioulnar joints
  
  • suppinator innervated by radial nerve
• flexion of forearm at elbow
  
  • brachioradialis is innervated by radial nerve
• adduction of hand at wrist
  
  • extensor carpi ulnaris

Question 56

AIN syndrome

• which nerve is lesioned?
• how do you test for it?

Answer 56

• AIN (Kiloh-Nevin) syndrome may be tested by the inability to make an “OK” sign with the hand
• I_nability to flex at the thumb interphalangeal joint, and weakness with flexing the fingers at the distal interphalangeal joints leads to a “triangle” sign_, without rounding of the thumb and index finger
• Bc the only muscle that causes flexion of the thumb at the interphalangeal joint is the flexor pollicis longus, which is innervated by the anterior interosseus nerve (AIN), a branch of the median nerve

Question 57

deep laceration to palm

Answer 57

• Check the intrinsic muscles and tendons of the hand. These are innervated by the median and ulnar nerves and are also separated into compartments.
• Thenar muscles: both median and ulnar nerve innervation
  
  • Median nerve –> Abductor Pollicis Brevis, Opponens Pollicis, Flexor Pollicis Brevis
    • Ask the patient to touch thumb and small finger tips together so the nails are parallel
  • Ulnar nerve –> Adductor pollicis
    • Have the patient hold paper between thumb base and radial side of 1st finger. Try to pull the paper away and see if they can hold it. When the adductor muscle is weak the thumb flexes at the IP joint to grab the paper (Froment’s sign)
• interosseous (ulnar)
• lumbricals
• hypothenar (ulnar)

Question 58

how could you evaluate sensory and motor functions for the radial nerve at the hand?

Answer 58

Radial (C5-C8)

• Motor: Extend the wrist.
  
  • or extend the thumb IP joint.
• Sensory: Test the dorsal webspace between the thumb and index finger

Question 59

which nerves are you testing?

1. Have the patient attempt opposition
2. Make an OK sign by having the patient touch the tip of the thumb to the tip of the index finger

Answer 59

1. recurrent branch of median nerve
2. AIN of median nerve

Radial nerve = C5-C8

median nerve = C5-T1

Ulnar nerve = C8-T1

Question 60

which nerve are you testing?

• Motor: Test by having patient spread fingers against resistance - dorsal interossei. Or test by having patients hold piece of paper between fingers - palmar interossei.
• Sensory: Palmar aspect of the little finger

Answer 60

ulnar nerve (C8-T1)

Question 61

signs of ulnar neuropathy in hand

Answer 61

• digits 4,5: weakened flexion and absent extension at the interphalangeal joints.
• Weakness of the flexor carpi ulnaris would also lead to some radial deviation of the wrist when the hand is flexed at the wrist.
• weakness of adduction (PAD) and abduction of the digits at the MCP joints (DAB) could be tested: holding a piece of paper between the digits against traction (to assess adduction) and maintaining finger-spreading against force (to assess abduction).
  
  • weakness of interossei muscles

Question 62

what are the 2 basic rules of nerve lesions?

Answer 62

• if nerve damage isn’t severe (compression or stretch) we expect to see sensory before motor findings
• the more proximal the lesion, the more clinical signs (of course!)

Question 63

What humeral fracture is associated with a median nerve lesion?

• sx?

Answer 63

Supracondylar fracture

as with carpal tunnel:

• ape thumb (lack of opposition)
• clawing for digits 2 & 3 (lack of flexors of anterior of forearm and lumbricals)

add more than carpal tunnel:

• hand of benediction when you ask to make a fist (thumb, digits 2 and 3)
  
  • bc flexor digitorum superficialis by median nerve, and half of flexor digitorum profundus

Question 64

name this nerve:

Answer 64

ulnar neuropathy

• This case describes potential overuse injury.
• The symptoms include tingling in the medial digits, as well as some potential weakness of intrinsic hand muscles.

Question 65

nursemaid’s elbow

Answer 65

• after yanking child, arm is pronated and extended
• d/t subluxation of radial head, out of annular ligament, which is weaker in kids
• Fix: suppinate and flex the arm to put back in place!

Question 66

medial epicondyle fracture

• what nerve is lesioned?
• what muscles does it innervate

Answer 66

Medial epicondyle = most common location for an ulnar nerve lesion

Question 67

ulnar nerve lesion

• where is it most commonly lesioned?
• what muscles are affected

Answer 67

• lesioned at medial epicondyle - from overuse, fracture, or bad ergonomics (resting on elbow for too long)
  
  • clinical case: drummer, jack-hammer-er
• muscles of forearm (flexor carpi ulnaris, medial half of FDP) and some intrinsic hand muscles could be affected
  
  • weakened flexion, and cannot extend digits 4,5

Question 68

name the nerve and artery that are affected:

Answer 68

• midshaft humoral fracture
• radial nerve lesion - it’s running through the spiral groove
  
  • wrist drop, finger drop at MCP
  • IP joints are fine - lumbricals
• profunda brachial artery may be impacted

Question 69

name this nerve:

Answer 69

• Anterior dislocation of the humerus and weakness/loss of ABduction above 15 degrees –> Think axillary nerve injury
  
  • innervates the deltoid
• inferior, anterior dislocation = most common dislocation of humerus

Question 70

axillary neuropathy

• motor function

Answer 70

• axillary nerve innervates deltoid & teres minor
  
  • Deltoid is more clinically significant - then you can’t do ABduction beyond 15^o
    
    • (abduction is initiated by supraspinatus, innervated by suprascapular nerve)
  • teres minor isn’t the only lateral rotator (ex: infraspinatus)

Question 71

shoulder dystocia during delivery of baby

• what are the main 3 nerves that are impacted
• clinical findings

Answer 71

• common cause of upper trunk lesion of brachial plexus (C5, C6 fibers)
• The most prominently impacted nerves:
  • _suprascapular nerve (_C5, C6),
  • musculocutaneous nerve (C5, C6)
  • axillary nerve (C5, C6)
  • radial nerve (C5, C6, C7, C8).
  • [dorsal scapular nerve (C5) and long thoracic nerve (C5, C6, C7) are generally not involved because they branch prior to the trunks. Impact on the median nerve is usually pretty minimal, as well, despite containing C6.]
• Erb-Duchenne palsy
  
  • arm is ADducted - because the deltoid (axillary) and supraspinatus (suprascapular) are paralyzed
  • arm and forearm are extended - because flexors or arm (biceps brachii and coracobrachilais) and flexors of forearm (biceps brachii and brachilalis) are innervated by musculocutaneous
  • arm is medially rotated - becaue the lateral rotators (infaspinatus - suprascapular) (teres minor - axillary) are paralyzed
  • waiter’s tip hand - just a side effect of the medially rotated, pronated forearm (bc strongest suppinator is the biceps brachii)
    
    • hand function actually fine

Question 72

Erb-Duchenne palsy

• cause
• 3 nerves involved
• what’s the position of the upper limbs and why

Answer 72

• due to neck getting hyperextended laterally - traction and stretching of C5, C6 roots
  
  • think of baby delivery pulling on neck, or falling onto neck
• lesions to suprascapular, musculocutaneous, axillary nerves
  
  • C5, C6 of upper trunk

Presentation:

• arm is ADducted, extended, medially rotated
• forearm is extended, pronated (bc strongest suppinator is the biceps brachii)
• waiter’s tip hand - side effect of the medially rotated arm, pronated because biceps brachii was the most powerful suppinator

Question 73

name this nerve lesion:

Answer 73

• The x-ray demonstrates a mass at the upper aspect of the right lung - “pancoast tumor” from lung cancer
• Given the difficulty moving hand, we should consider C8 and T1
• Could be a C8/T1 radiculopathy or a lower trunk lesion
  
  • affects median and ulnar nerves

Question 74

upper trunk lesions affect which nerves

Answer 74

• suprascapular
• musculocutaneous
• axillary

Question 75

Name three actions at the joint formed by bones 6 and 7 that will be weakened in a patient with compression of the upper trunk of the brachial plexus.

Answer 75

Flexion, Abduction, Lateral rotation / Supination

Question 76

lower trunk lesions

• causes
• affect mainly which nerves
• clinical presentation

Answer 76

• think of pulling hard on arm - traction applied to an abducted upper limb
• The lower trunk is formed from the union of the C8 and T1 roots (ventral rami).
• It most significantly contributes to the median nerve (C6, C7, C8, T1) and ulnar nerve (C8, T1)
  
  • difficulty moving hand
• Clinical:
  
  • Klumpke’s palsy - clawing of all digits
  • Horner syndrome - ptosis (drooping of eyelid), miosis (narrowing of pupil)

Question 77

this could cause what lesions?

what sx are associated?

Answer 77

• traction on ABducted arm can lead to lower trunk lesion (C8, T1)
• Klumpke’s palsy (klumpe the monkey hanging from tree branch)
  
  • clawing of all digits
• Horner syndrome - loss of sympathetic innervation to the head and neck (T1-L2)

Question 78

name this nerve lesion:

Answer 78

• Femoral nerve lesion - femoral neuropathy
  
  • dermatome of anterior thign, medial leg
    
    • saphenous nerve continues as cutaneous only, for medial leg
  • “giving out” of the limb might be due to effects on the quadriceps muscles
• Anterior compartment of the thigh
  
  • overall: flexion at the hip, extension at knee
    
    • nuances: pectineus helps with ADduction, sartorius helps with flexion at the knee (also flexion at the hip, and lateral rotator at the hip)
• can also be caused by femoral hernia

Question 79

possible causes for femoral nerve lesion,

and clinical findings

Answer 79

• femoral hernia
• abscess in right psoas muscle
• difficulty walking - d/t quadriceps
• burning in anterior thigh, medial leg dermatome

Question 80

name this lesion:

An 80-year-old man with a history of metastatic urothelial carcinoma of the bladder complains of tingling in the medial thigh. Previous imaging has identified diffuse lymphadenopathy in the pelvis.

Physical examination demonstrates weakness of thigh adduction on the left side

Answer 80

• obturator nerve
  
  • weakness of thigh ADduction
  • not common
• innervates ADductors
  
  • obturator externus (also helps with lateral rotation at hip)
    
    • not the obturator internus, has its own branch
  • adductor brevis, longus, magnus
  • gracilis (also helps with flexion of knee)
• small dermatome in medial thigh

Question 81

name this lesion:

what nerves run through the gluteal region?

Answer 81

• sciatic - tibial and common fibular
  
  • Tibial –>
  • Common fibular –>
• gluteal nerves
  
  • superior gluteal nerve –>
  • inferior gluteal nerve –> gluteus maximus

Question 82

What are the clinical findings of an inferior gluteal nerve injury?

Answer 82

• Difficulty getting up from a chair without using upper limbs
  
  • because gluteus maximus is our major extensor from flexed position

Question 83

What are the clinical findings of an superior gluteal nerve injury?

Answer 83

• Trendlenburg waddling gait
  
  • because superior innervates gluteus medius and gluteus minimus and tensor fasciae latae - ABduction to stabilize the pelvis
• trunk slumps to the opposite side, as rotate around center of gravity
  
  • so if you stand on the lesioned side (ex: right side), the opposite hip will drop (non-lesioned side), because right gluteus medius/minimus fails to pull the right pelvis down

Question 84

Where is the common fibular nerve most commonly lesioned?

What are the clinical findings?

Answer 84

• Fracture at the neck of the fibula
  
  • thereafter it divides into deep and superficial
    
    • deep –> anterior compartment of leg
      
      • ​dorsiflexors –> foot drop
      • and some weakness in inversion, but tibial helps with this
    • superficial –> lateral compartment of leg
      
      • ​everters
• weakness with dorsiflexion and eversion
• Steppage/slapping gait
  
  • The patient experiences a foot drop; to compensate, the knee and/or hip are often flexed more than usual to pull the toes off the ground.
  • Because of the lack of dorsiflexion, the normal heel-to-toe progression of stepping on the foot is replaced with a single “flat” placement of the foot on the ground.
• sensory changes over anterolateral leg and dorsum of foot
• btw the short head of the biceps femoris is innervated by common fibular nerve, but wouldn’t be involved because it’s more proximal

Question 85

Answer 85

• fracture at neck of fibula –> common fibular nerve injury –> affects superficial fibular nerve too –> weakness in eversion

Question 86

steppage / slapping gait

• caused by lesion to what nerve?
• where is the fracture most likely?

Answer 86

• lesion to common fibular nerve
• fracture over neck of fibula
• can’t dorsiflex at the ankle joint
• steppage gait due to foot drop
  
  • entire foot slaps down flat
  • to avoid running over toes, raises lower limb higher

Question 87

clinical findings with lesion to tibial nerve?

Answer 87

• can’t stand on tip toes
  
  • loss of ankle and toe plantar flexion - flexor digitorum longus
  • Standing on the tip-toes is a test for tibial nerve function, as the tibial nerve innervates the strongest plantar flexors of the foot (gastrocnemius and soleus).
• weakness inverting foot
  
  • tibialis posterior, flexor hallicus longus, flexor digitorum longus
  • (but tibialis anterior from deep fibular)
• sensory changes to posterior leg and sole of foot

Question 88

Answer 88

The answer is (D).

The Anterior Interosseus Nerve is a muscular nerve that arises from the median nerve and innervates three muscles of the anterior forearm: the flexor pollicis longus, the lateral half of the flexor digitorum profundus, and the pronator quadratus. There is no cutaneous distribution for this nerve.

(A)The superficial fibular nerve’s dermatome is the anterolateral leg and much of the dorsum of the foot.

(B)The deep fibular nerve’s dermatome is the webspace between the hallux and the second digit (the “flip-flop” distribution)

(C)The musculocutaneous nerve’s dermatome is the lateral forearm. (lateral antebrachial cutaneous… medial antebrachial cutaneous nerve comes straight from the medial cord of the brachial plexus)

(D)(correct answer)

(E)The tibial nerve’s dermatome is the sole of the foot and some of the posterior leg.

Question 89

Answer 89

The answer is (C).

The primary deficits in this median nerve lesion will include absence of flexion and extension of the second and third digits, weakened flexion of the fourth and fifth digits, an “ape” thumb, and some weakness with pronation. If asked to make a fist, the patient will show the “Hand of Benediction,” with somewhat extended, somewhat flexed second and third digits, and weakly flexed fourth and fifth digits.

(A)Pronation may be mildly weakened because of denervation of the pronator quadratus, but the pronator teres can generally create enough power that this symptom is generally subtle, if present at all.

(B)Supination should not be impacted by this lesion, as the supinator and biceps brachii are innervated by the radial and musculocutaneous nerves, respectively.

(C)(correct answer)

(D)Finger spreading is accomplished by the dorsal interossei muscles, which are innervated by the ulnar nerve.

(E)“Crossing” of the second and third digits means that the second digit is adducted, while the third digit is abducted radially; these actions are accomplished by the palmar and dorsal interossei muscles, respectively, which are innervated by the ulnar nerve.

Question 90

Answer 90

The answer is (B).

A fracture of the surgical neck of the humerus may lesion the axillary nerve, which innervates the deltoid (and the teres minor). The deltoid is responsible for abduction above approximately 15 degrees (and, by extension, maintaining the position of the upper limb above 15 degrees).

(A)Midshaft humeral fractures are associated with radial nerve lesions; clawing of digits 4 and 5 is associated with ulnar nerve lesions.

(B)(correct answer)

(C)Medial epicondylar fractures are associated with ulnar nerve lesions; the middle finger is within the dermatomes of the median (palmar surface and nail bed) and radial (dorsal surface) nerves.

(D)Lateral epicondylar fractures do not have any classically associated nerve lesions; finger spreading is accomplished by the ulnar nerve.

(E)Supracondylar fractures are associated with median nerve lesions; wrist drop is associated with radial nerve lesions.

Question 91

Answer 91

The answer is (A).

If the left superior gluteal nerve is lesioned, the left gluteus medius, gluteus minimus, and tensor fasciae latae muscles will be weakened. When an individual with this lesion stands on only the left leg, the affected muscles are unable to abduct the trunk and keep the pelvis level.

(B)A left-sided gluteal nerve lesion will be demonstrated when the patient stands on the left leg.

(C)Standing on the tip-toes is a test for tibial nerve function, as the tibial nerve innervates the strongest plantar flexors of the foot (gastrocnemius and soleus).

(D)See choice (C).

(E)An inferior gluteal nerve lesion is associated with difficulty arising from a chair due to denervation of the gluteus maximus muscle.

Question 92

Answer 92

The answer is (D).

The two abductors of the arm at the shoulder are the deltoid and the supraspinatus, which are innervated by the axillary and suprascapular nerves, respectively. Both of these nerves are composed of C5 and C6 fibers, which are lesions in an upper trunk plexopathy.

(A)Clawing is a more prominent feature of median and ulnar neuropathies, or a lower trunk plexopathy.

(B)The arm should be medially rotated in an upper trunk plexopathy due to unopposed activity of the subscapularis; the infraspinatus and teres minor, innervated by the suprascapular and axillary nerves, respectively, are both weakened by an upper trunk plexopathy.

(C)The medial arm corresponds most closely with the T1 dermatome, not the C5 and C6 dermatomes.

(E)The axillary nerve (and the radial nerve, less so) are impacted by an upper trunk plexopathy, and are composed of posterior division fibers.

Question 93

Answer 93

Lesion to radial nerve! Runs with profunda brachial artery, in the spiral groove)

The answer is (E).

“Saturday night palsy” is a proximal radial neuropathy. Extension at the proximal interphalangeal joints is accomplished by the lumbricals, which are innervated by the median and ulnar nerves.

(A)Extension at the elbow is accomplished by the triceps brachii, innervated by the radial nerve.

(B)Extension at the wrist is accomplished by the extensor carpi radialis longus and brevis, and extensor carpi ulnaris, which are innervated by the radial nerve.

(C)Extension at the metacarpophalangeal joints is accomplished by the extensor digitorum, extensor indicis, and extensor digiti minimi, which are innervated by the radial nerve.

(D)Extension at the interphalangeal joint of the thumb is accomplished by the extensor pollicis longus, which is innervated by the radial nerve.

Question 94

Answer 94

The answer is (A).

The deep fibular nerve is responsible for dorsiflexion; its dermatome is just the space between the first and second toes (the “flip-flop” distribution). The “high-stepping” gait described by this patient is a common compensatory mechanism to avoid scraping the foot on the ground.

(A)(correct answer)

(B)The superficial fibular nerve innervates everters of the foot and has a much more extensive dermatome than described.

(C)The femoral nerve is responsible for flexion at the hip and extension at the knee; its dermatome includes the anterior thigh and medial leg.

(D)The obturator nerve is responsible for adduction at the hip; its dermatome is a small area in the medial thigh.

(E)The tibial nerve is responsible for extension at the hip, flexion at the knee, and plantar flexion; its dermatome includes the sole of the foot and some of the posterior leg.