ICL 4.6: UE Entrapment Neuropathies

Question 1

what are the 3 types of nerve connective tissue?

Answer 1

1. endoneurium
2. perineurium
3. epineurium

Question 2

what is the endoneurium?

Answer 2

a type of nerve connective tissue

connective tissue surrounding each individual axon and its mylin sheath

Question 3

what is the perineurium?

Answer 3

strong, protective connective tissue

it surrounds bundle or fascicles of myelinated and unmyelinated nerve fibers; middle layer –> so it’s a bundle of axons covered in endoneurium

it strengthens the nerve and acts as diffusion barrier –> individual axons may cross from one bundle to another along its course

Question 4

what is the epineurium?

Answer 4

loose connective tissue surrounding entire nerve; most outside layer

it holds fascicles together

protects nerve from compression

Question 5

what’s the most common nerve entrapment syndrome?

Answer 5

carpal tunnel syndrome

Question 6

what are the 3 classifications of nerve injuries?

Answer 6

1. neurapraxia
2. axonotmesis
3. neurotmesis

Question 7

what is the etiology and description of neurapraxia?

Answer 7

aka conduction block

the nerve gets compressed so it can’t relay the message down the axon

so like when you fall asleep and your nerve gets pinched and you wake up and your hand is tingling

axon is intact; might have local myelin injury

you’ll recover within a few hours; pretty mild injury

Question 8

what is the etiology and description of axonotmesis?

Answer 8

nerve crush injury

you do have disruption of the axon and protective tissue damage

endoneurium and perineurium is intact but axon and myelin are effected so axons will start to die = Wallerian degeneration occurs

you won’t be able to conduct any type of signal down the nerve

takes 1 mm a day to heal the nerve between the nerve to the muscle it innervates

Question 9

what is the etiology and description of neurotmesis?

Answer 9

nerve transection injury

your nerve is totally cut –> epineurium is fine but endoneurium and perineurium are damaged

axon is interrupted, connective tissue is damaged and no conduction down the nerve

regrowth is really difficult so patients will have to have surgery to reattach nerves

Question 10

what are the 5 places of entrapment of the median nerve?

Answer 10

1. ligament of struthers (LOS)
2. bicipital aponeurosis (lacertus fibrosis)
3. pronator teres (PT) Syndrome
4. AIN syndrome
5. carpal tunnel

Question 11

how does the median nerve get entraped at the ligament of struthers? what effects will you see if that happens?

Answer 11

there is a 2 cm bone spur 3-6 cm proximal to medial epicondyle connected by a ligament to the medial epicondyle in 1% of population and the median nerve passes under the ligament and can get entrapped there

the nerve becomes entrapped with brachial artery under ligament; so pulse might be diminished and patients might complain of dull achy sensation in forearm from nerve entrapment

rehab or surgery is how you fix it

weakness:
1. FDP and FDS weakness = grip weakness

2. FCR weakness = wrist flexion weakness
3. FDP weakness = 2nd and 3rd digit flexion weakness

Question 12

how does the median nerve get entraped at the lacertus fibrosis? what effects will you see if that happens?

Answer 12

when there’s thickening of the antebrachial fascia that attaches your biceps to ulna –> the antebrachial fascia overlies the median nerve in the proximal forearm in the elbow region

you could also get a hematoma that compresses the nerve if someone punctures the veins in the area

treat with rehab or surgical release or stretching the ligament

weakness:
1. FDP and FDS weakness = grip weakness

2. FCR weakness = wrist flexion weakness
3. FDP weakness = 2nd and 3rd digit flexion weakness

looks just like LOS entrapment!

Question 13

how does the median nerve get entraped at the pronator teres? what effects will you see if that happens?

Answer 13

so your median nerve actually passes between the 2 heads of the pronator teres muscle on its way down to the FDS and it can get compressed inside the muscle or by the fascial bands that connect to the FDS

patients will complain of dull ache in proximal forearm exacerbated by forceful pronation or finger flexion (FDS)

weakness = all median innervated muscles in forearm and hand except pronator teres*

Question 14

how does the median nerve get entraped at the AIN? what effects will you see if that happens?

Answer 14

pure motor syndrome

can be caused by idiopathic, fracture, laceration, compression

Exam: +ve OK sign, difficulty forming a fist d/t inability to approximate thumb and index finger

FDP and FDL will flex distal portion of fingers so they should be able to make OK sign but if they can’t they’ll compensate with the ulnar nerve and will extend at the DIP and have a more flattened OK sign

they also won’t be able to fully flex when you ask them to make a fist because they won’t be able to flex DIP so they’re finger will be sticking out

Question 15

what are some of the causes of carpal tunnel?

Answer 15

1. Idiopathic
2. Increased volume within the carpal tunnel
   ex. thyroid disease, CHF, renal failure, mass (tumor, hematoma), and pregnancy (usually occurs at 6 mos and resolves postpartum)
3. decreased volume within the carpal tunnel
   ex. fracture, arthritis, rheumatoid tenosynovitis
4. Double crush syndrome from DM, Cervical Radiculopathy, and TOS

Question 16

what’s the clinical presentation of carpal tunnel?

Answer 16

1. gradual and often at night
2. first 3 digits often effected: night pain or aching, numbness, tingling pain in hand, pain in forearm toward shoulder
3. feels need to ”shake it off”
4. weakness LOAF muscles

**severity of CTS symptoms does not necessarily correlate with severity of EDX findings

Question 17

what structure is not within the carpal tunnel?

A. FDS

2. FDP
3. FCR
4. FPL
5. median nerve

Answer 17

flexor carpi radialis

Question 18

what 5 tests can you do to test for carpal tunnel?

Answer 18

1. Tinel’s
2. Phalen’s
3. Tourniquet’s test = inflate BP cuff reproduction of symptoms at 1 minute
4. carpal compression test aka Durken’s compression test
5. reverse Phalen’s test

you usually want 2 positive tests to diagnose with CTS

Question 19

how do you treat carpal tunnel syndrome?

Answer 19

1. rehab
   - orthotics: neutral resting hand splints overnight
   - medications: NSAIDS, oral steroids, steroid injection, diuretic, vitamin B6
   - ergonomic modifications
   - treat underlying medical disorder
2. surgery

indications = muscle atrophy, severe pain and failure of conservative treatment

limited symptomatic relief and return of muscle strength with severe median nerve damage and profound muscle atrophy

Question 20

what are the 3 sites of entrapment of the ulnar nerve?

Answer 20

1. arcade of struthers
2. cubital tunnel
3. Guyon’s cannal

Question 21

what’s the path of the ulnar nerve?

Answer 21

it descends along medial head of triceps within Arcade of Struthers

then it continues posteriorly through the retrocondylar groove and through the cubital tunnel in the forearm

it then passes into the hand via Guyon’s canal

Question 22

how does the ulnar nerve get entrapped at the arcade of struthers? what effects will you see if that happens?

Answer 22

there’s a fascial band in the medial arm that connects brachialis to tricep brachii and the ulnar nerve can get compressed under this fascial band

interventions may include rehab or surgical release of AOS

clinical presentation:
1. involvement of ALL ulnar nerve innervated muscles; since this is very proximal all the ulnar muscles will be effected

2. wrist flexion w/ radial deviation (FCU weakness)
3. abnormal sensation in all sensory braches of ulnar nerve
4. ulnar claw hand: unopposed pull of EDC causes partial finger flexion of 4th and 5th PIP and DIP joint d/t MCP extension

Question 23

what is the Froment’s sign?

Answer 23

Inability to hold piece of paper by thumb and index finger with pure thumb adductions (APL)

the patient will instead substitute the median innervated FPL causing flexion of DIP joint

Question 24

what is Wartenberg’s sign?

Answer 24

inability to aduct the pinky because interossei is weakened

Question 25

how does the ulnar nerve get entrapped at the cubital tunnel? what effects will you see if that happens?

Answer 25

this is the most common site of elbow entrapment

the ulnar nerve gets compressed beneath the proximal edge of FCU aponeurosis or arcuate ligament –> the cubital tunnel is bordered by medial epicondyle and olecranon with overlying aponeurotic band

treat with rehab or surgical release

clinical presentation:

1. all ulnar nerve innervated muscles +/- FCU are effected
2. similar complaints as AOS entrapment
3. Tinel’s sign at ulnar groove

Question 26

how does the ulnar nerve get entrapped at Guyon’s canal? what effects will you see if that happens?

Answer 26

proximal extent of the transverse carpal ligament and ends at the aponeurotic arch of the hypothenar muscles

different branches of ulnar nerve can be injured at wrist

can be caused by cyclist’s palsy, wrist ganglions, RA, or trauma

clinical presentation depends on the type you have (there are 3)

Question 27

what are the 3 types of Guyon’s canal ulnar compressions?

Answer 27

1. involvement of the deep ulnar branch, hypothenar and sensory
2. involvement of deep ulnar motor branches
3. involvement of the superficial ulnar sensory branch

Question 28

what are the 5 entrapment sites of the radial nerve?

Answer 28

1. crutch palsy
2. 2. Spiral groove – Honeymooner’s palsy
3. radial tunnel
4. PIN syndrome
5. 5. Cheiralgia Paresthetica

Question 29

what is crutch palsy?

Answer 29

when you’re compressing on the posterior cord of brachial plexus; most commonly affecting radial nerve

you will see weakness in ALL radially innervated muscles including triceps brachii

sensation is decreased over posterior arm and forearm

interventions: focus on rehab, discontinue crutch use, static cock-up splint or dynamic splinting

Question 30

what is spiral groove/honeymooner’s palsy?

Answer 30

Arm positioned over a sharp ledge like a chair back or head on humerus when you’re cuddling with someone –> you can also get them from injections, compression, or fracture

you will see weakness in radial innervated muscles below the spiral groove – triceps and anconeus are spared though!

weakness of elbow flexion (Brachialis**), supination (supinator), wrist drop (ECRL, ECRB, ECU) finger extension (EDC)

sensory deficits in dorsal aspect of hand and posterior forearm

Question 31

the brachialis muscle is innervated by which two nerves?

Answer 31

1. radial

2. musculocutaneous

Question 32

the pectoralis major muscle is innervated by which two nerves?

Answer 32

1. medial pectoral

2. lateral pectoral

Question 33

the flexor digitorum profundus muscle is innervated by which two nerves?

Answer 33

1. median nerve (AIN)

2. ulnar nerve

Question 34

the lumbricals muscle is innervated by which two nerves?

Answer 34

1. median

2. ulnar

Question 35

the flexor pollicis brevis muscle is innervated by which two nerves?

Answer 35

1. median nerve

2. ulnar nerve

Question 36

how is the radial nerve compressed at the radial tunnel? what happens?

Answer 36

radial nerve anatomy at elbow is highly variable – it runs through an intramuscular septum b/w the brachialis and brachioradialis then branches into PIN and superficial radial branch before or after traveling through the intramuscular septum

symptoms may mimic a resistant lateral epicondylitis = tennis elbow

Question 37

what is PIN syndrome?

Answer 37

purely motor syndrome!!!

the radial nerve can be compressed at arcade of Frohse of the supinator

it can also be compressed by a lipoma, ganglion, cyst, RA, or Monteggia fracture

Weakness in PIN innervated muscles – EDC, EIP, ECU, EPB, EPL, APL = wrist drop syndrome (but supinator muscle will be fine)

you may also see pseudo claw-hand because of weak distal extensors and radial deviation with wrist extension (flexion is stronger than extension)

Question 38

what is a Monteggia fracture?

Answer 38

Fracture of proximal 1/3 of ulna and dislocation of radial head towards the ulnar

it’s a FOOSH with forearm locked in full pronation

this could cause PIN syndrome

Question 39

what is 5. Cheiralgia Paresthetica?

Answer 39

aka wristwatch syndrome

it’s compression at wrist from watch, tight handcuffds, peripheral IV placement

it’s a PURE sensory syndrome so you’ll get burning and/or tingling on dorsal radial aspect of hand

Question 40

what’s the course of the axilary nerve?

Answer 40

Passes inferior to GHJ through quadrilateral space of axilla and posterior aspect of humerus

Question 41

what could cause axillary neuropathy?

Answer 41

injury can be traction or compression from shoulder dislocation, humeral head fracture, improper axillary crutch use

involves deltoid and teres minor so you might have weakness of shoulder flexion & abduction (deltoid) & external rotation (teres minor)

interventions include rehabilitation, surgical decompression and discontinuation of crutch use

Question 42

what is the course of the suprascapular nerve?

Answer 42

it runs beneath trapezius through scapular notch then wraps around the spinoglenoid notch

it’s the only peripheral nerve injury at trunk level

Question 43

what is effected when the suprascapular nerve get compressed?

Answer 43

Abduction weakness because of the supraspinatus weakness

external rotation weakness because of infraspinatus weakness

Question 44

where is the suprascapular nerve compressed when both the supraspinatus and infraspinatus are affected?

Answer 44

scapular notch

if it was compressed at the spinoglenoid notch then the supraspinatus would be fine because it would’ve already been innervated since it’s proximal to the spinoglenoid notch

Question 45

what can cause suprascapular palsy?

Answer 45

Forced scapular protraction

Penetrating wounds

Improper crutch use

Traction rotator cuff rupture

Erb’s palsy

Spinoglenoid ganglions

Hematoma

Scapular or spinoglenoid notch entrapment

Paralabral cyst

Sports with repetitive overhead movement most commonly injures branches to Infraspinatus

Question 46

what is the course of the musculocutaneous nerve?

Answer 46

travels along medial aspect of the humerus = Coracobrachialis, Biceps Brachii, Brachialis

it then continues anterior to antecubital fossa lateral to biceps tendon