Upper Limb Nerves

Question 1

What is Parsonage Turner syndrome?

Answer 1

Acute brachial plexus neuritis.

aka brachial neuritis, neuralgic amyotrophy

Presentation:

• sudden onset of intense pain that subsides in 1 to 2 weeks
• typically awakens people from sleep
• followed by weakness for a period of up to 1 year in the muscle that is supplied by the involved nerve

Physical exam

severe weakness of the external rotators and abductors

can have decreased sensation (up to 75% of patients)

especially in lateral antebrachial cutaneous nerve

commonly affects more than one nerve branch

outcomes

90% of patients recover full muscle strength and function by 3 years with no residual pain or deficits

only 35% of patients recover at 1 year

Question 2

Name the common sites of compression of the median nerve (5)?

What symptoms/signs will the patient have?

Answer 2

• DIFFERS FOM AN AIN PALSY. THIS IS AKA PRONATOR SYNDROME. Should have predominantly sensory symptoms which can be provoked, also has aching pain in forearm and sensory disturbance over palm of hand which can differentiate from carpal tunnel syndrome. ALSO HAVE PRONATOR WEAKNESS and WEAKNESS OF HAND INSTRINSICS LIKE AN AIN PALSY.

Can also have hand instrinisc weakness if there is a martin gruber anastamosis (due to the takeover of ulnar innervated hand intrinsics by the median-to-ulnar connection)

1. • supracondylar process of the humerus
2. • ligament of struthers
3. • Lacertus fibrosis
4. • between ulnar and humeral heads of pronator
5. • FDS aponeurotic arch (sublimis bridge)
6. • (then in the wrist - carpal tunnel)

Question 3

Name the common sites of compression of the AIN (8)?

What is the common presentation, how does it differ from a median nerve proper lesion?

Answer 3

AIN compression syndrome is different from Median nerve proper lesion (aka Pronator syndrome) as there is weakness in all AIN supplied muscles (FPL,FDP 1/2 and PQ) and NO sensory symptoms.

There may be only intrinsic weakness if there is an incomplete palsy or a reverse martin gruber anastomosis (i.e Marinacci anastomosis) is present (in 15% of ppl, where Ulnar nn axon cross over to the AIN/Median to innervate certain muscle groups)

Depending on where the AIN comes off, sites of compression can be:

1. edge of lacertus fibrosis
2. tendinous edge of pronator teres
3. FDS arch
4. accessary head of FPL (Gantzers)
5. accessory muscle from FDS to FDP
6. Abberant mm (FCRB, palmaris profundus)
7. thrombosed ulnar or radial artery
8. abberant vessels

Answer from our lecture series:

1. Accessory muscles: Gantzer’s accessory FPL muscle
2. FDS
3. Aberrant vessels
4. Pronator teres

Question 4

What are the common sites of compression of the Radial nerve (PIN compression syndrome)(5)?

Answer 4

Fibrous bands anterior to radial head

Recurrent radial vessels (Leash of Henry)

ECRB

Arcade of Frohse (proximal edge of supinator)

distal edge of supinator

Question 5

What is the arcade of struthers?

What is the ligament of struthers?

Answer 5

Arcade of struthers:

Thickening of the deep investing fascia of the arm - Extends from the medial head of triceps to the intermusular septum Present in 70% of the population 1.5-2cm in width, 8-10cm proximal to the medial epicondyle.

where the ulnar n crosses lateral IM septum to go from anterior to posterior compartment - potential site of compression of ULNAR NERVE

Ligament of struthers:

This is a ligament from the supracondylar process (1% of pop) to the humerus and is a potential site of compression of the MEDIAN nerve

Question 6

What is Froment’s sign? What does it indicate?

Answer 6

Seen with an ulnar nerve palsy with paralysis to the adductor pollicis.

There is compensatory flexion of the thumb IP joint when asked to grab a piece of paper.

***This is in contrast to an AIN palsy when the patient will be unable to grasp a piece of paper using a pincer grip due to loss of the long flexors***

Question 7

Describe the pathogenesis of ulnar claw:

Answer 7

• MCP hyperextension: loss of intrinsics (responsible for MCP flexion)
• IP Flexion: Unopposed action of long extensors. Loss of lumbricals causes IP flexion

High vs low ulnar nerve lesion:

‘the closer to the Paw, the worse the Claw’.

This is because higher up you lose innervation to FDS to the ulnar two fingers which is a deforming force and functions to flex the IP joints. If you have a lower lesion then FDS is intact, causing more deformity and the “Worse the claw”

In a lower ulnar nerve lesion you get the Hand of benediction: - Hyperextension of MCPs & Flexion of IP joint - Due to loss of intrinsics and ulnar 2 lumbricals

Caused Low lesion of ulnar nerve causing above paralysis, exacerbated when asked to extend fingers.

Hand of benediction can also be seen with a median nerve lesion when asked to make a fist

Question 8

What is the ulnar paradox?

Answer 8

High ulnar nerve lesion causes a paradoxically more benign looking hand (although the pathology is worse) - High ulnar nerve lesion takes out FDP also, causes less of an IP flexion contracture and a benign looking hand.

“The lower the claw, the worse the paw”

Question 9

What is an anconeus epitrochlearis?

Answer 9

Anomalous muscle found in 10% of patients - Arises from medial border of olecranon & adjacent triceps - Inserts into medial epicondyle May be a muscular or fibrous structure

ANCONEUS proper is on the other side of the elbow. Dont get them confused

like a “muscular osborne’s ligament”

Question 10

What is pronator syndrome?

Answer 10

Compression of median nerve at elbow

Main dDx: CTS

• Parasthesia in median nerve distribution Different from CTS b/c:
• Aching pain over proximal volar forearm
• Sensory disturbance over palmar cutaneous branch distribution (this arises 4-5cm proximal to carpal tunnel)
• Lack of night symptoms

Question 11

What is AIN syndrome?

Answer 11

Compression of AIN

Weakness of FPL, FDP to middle and index fingers, and PQ

Cannot make OK sign

Question 12

When do you see the “Hand of Benediction”

Answer 12

This refers to a median nerve palsy where you lose the ability to flex D1-3. This sign is brought out by asking the patient to make a fist. This looks very simliar to a claw hand but they are different as clawing is due to ulnar nerve lesion. A low ulnar nerve lesion is often also referred to as the hand of benediction. Worse with asking the patient to extend the fingers.

Question 13

Where does the AIN originate?

Answer 13

4cm distal to medial Epicondyle, but generally quite variable where it branches off the median n proper, usually somewhere around the 2 heads of pronator

Question 14

If you ask a patient to hold a piece of paper between their index and thumb and they do this, what is your diagnosis? what is this sign called?

Answer 14

AIN nerve palsy

Subtle weakness of the FPL and index finger FDP may be uncovered by asking the patient to pinch a sheet of paper between his thumb and index finger using only the fingertips and then trying to pull the paper away

This is NOT froment’s sign!

Question 15

What are the boundaries of the the radial tunnel?

Cubital tunnel?

Carpal Tunnel?

Guyon’s canal?

Answer 15

Cubital tunnel:

Floor:

• Medial joint capsule
• MCL
• Olecranon

Roof:

• Osborne’s ligament

Carpal Tunnel

Floor:

• Carpal bones

Roof:

• Transverse Carpal ligament (flexor retinaculum)

Radial Border:

• Scaphoid tubercle
• Trapezium Ridge

Ulnar Border:

• Hook of Hamate
• Pisiform

Guyon’s Canal

Roof:

• volar carpal lig

Floor:

• Transverse Carpal ligament

Radial:

• hamate

Ulnar:

• pisiform

Question 16

What is the flexor retinaculum in continuity with proximally?

What is a danger distally when releasing the carpal tunnel? How do you landmark this danger?

Answer 16

• In continuity with the antebrachial fascia.
• Danger at the distal edge is the superficial palmar arch.
• Dont go distal to Kaplans Cardinal line. (evidence that this is a better surface landmark for the superficial palmar arch than the deep palmar arch)

Hand. 2010 Jun; 5(2): 155–159.

The Clinical Application of Kaplan’s Cardinal Line as a Surface Marker for the Superficial Palmar Arch

Question 17

What is the Martin Gruber Anastamosis?

What is it’s clinical significance?

Answer 17

Occurs in 10 to 44% of people

Branches from the median to ulnar nerve in the forearm. Can have 2 patterns:

1. Median nn in the prox forearm to the ulnar nerve in the middle to distal third
2. From AIN to ulnar nerve

• THE RESULT IS THAT THE MEDIAN NERVE ENDS UP INNERVATING HAND INTRINSICS

Clincial significance

• High ulnar n. laceration:

Preservation of intrinsic muscle function, along with loss of function of the FCU and FDP to the ulnar two fingers

• High median n. laceration:

Loss of some of the intrinsic muscles usually innervated by the ulnar n.

In the literature, some researchers cited the clinical importance of MGA. The intrinsic muscles of the hand were completely unaffected by median lesions. A lesion of the median nerve situated proximal to the departure of the communicating branch would affect the median thenar muscles, whereas a lesion below that would not

Question 18

What is the Marinacci Anastamosis?

Answer 18

• A reverse Martin gruber from the ulnar to the median nerve.
• THE ULNAR NERVE ENDS UP INNERVATING THE THENAR MUSCLES

Question 19

What is the Riche-Cannieu Anastamosis?

Answer 19

This is a communication between the deep branch of the ulnar nerve and the recurrent branch of the median nerve.

This can lead to a hand with complete ulnar intrinsic innervation. I.e the thenar eminence is ulnar based. This can be a problem with compression neuropathies at the wrist i.e guyon’s canal leading to weakness of the thenar eminence

Question 20

Where does the AIN arise?

Where does it then run?

What does it innervate?

Answer 20

Usually arises 4cm distal to the medial epicondyle

Arises from the median nerve at a variable level as the nerve passess beween the heads of pronator teres. It then runs along the volar aspect of the IOM deep to FDP

Innervates FPL, lateral half of FDP and pronator quadratus (deep muscles)

Question 21

What does Median nerve innervate in the forearm and hand and what is the order of supply?

Answer 21

PT

FCR

PL

Then the AIN takes over and supplies FDP (1 and 2), FPL and PQ

In the hand the median nerve proper supplies:

APB, FPB, OP, Lumbricals 1 and 2

Question 22

What is the difference between the Hand of Benediction and an Ulnar claw hand?

Answer 22

These two entities look very similar however

Benediction - median nerve. Only brought out if asked to make a fist. Unable to flex D1-3 due to loss of the long flexors. Only for high median nerve lesion before bifurcation to the AIN.

Claw hand - ulnar nerve. Spontaneous. MCP hyperextended, IP flexed all due to the overpull of the volar long flexors.

To explain why this occurs, we need to consider the muscles that are affected by an ulnar nerve lesion at the wrist:

Medial two lumbricals: Flexes at the MCP joints and extends at the IP joints of the little and ring fingers.

Interossei: Abducts and adducts the fingers.

Hypothenar muscles: Flexes, abducts, and opposes the little finger.

Adductor pollicis: Adducts the thumb.

Ulnar Claw

D4 and 5 are hyperextended at the metacarpophalangeal (MCP) joint, and flexed at both interphalangeal (IP) joints.

In the ulnar claw, the important muscles to consider are the medial lumbricals. If these muscles are paralysed, there is a loss of flexion at the MCP joints, and a loss of extension at the IP joints. This leads to an imbalance between the intrinsic and extrinsic muscles of the hand – producing the claw deformity:

The MCP joints are hyperextended due to unopposed extension from the long extensor muscles in the posterior compartment of the forearm.

The IP joints are flexed due to unopposed flexion from the long flexor muscles in the anterior compartment of the arm. The extensor muscles cannot extend at the IP joints as their energy is dissipated in hyperextending the MCP joints.

The ulnar claw only occurs in the little and ring fingers, as the lateral two lumbricals are innervated by the median nerve.

Hand of Benediction

The hand of benediction occurs as a result of median nerve damage at the elbow. In contrast to the ulnar claw, which is produced spontaneously, the hand of benediction is only apparent if the patient is asked to make a fist.

To explain how the hand of benediction is produced, we need to consider the muscles affected if the median nerve is lesioned at the elbow:

Long flexors in the anterior compartment of the arm (except the medial half of the flexor digitorum profundus and the flexor carpi ulnaris).

Lateral two lumbricals: Flexes at the MCP joints and extends at the IP joints of the index and middle fingers.

If the patient is asked to make a fist, they will be able to flex the little and ring fingers. This action is performed by the medial half of the flexor digitorum profundus and the medial two lumbricals.

The patient will not be able to flex the index and middle fingers. Thus, the patient displays a claw shape, where the little and ring fingers and flexed, the index and middle fingers extended.

Question 23

What is ulnar paradox?

Answer 23

When there is a high ulnar nerve lesion and you get less clawing than with a more distal lesion. This is due to the loss of the FDP to D4-5.

“The closer to the paw, the more the claw”

Ulnar Paradox

The ulnar claw is a deformity produced by an ulnar nerve lesion at the wrist. We shall now look at what happens if the ulnar nerve is damaged more proximally – at the elbow.

In a high ulnar nerve injury, some muscles in the anterior forearm are paralysed (in addition to the hand muscles mentioned above):

Medial half of flexor digitorum profundus: Flexes at the distal IP joints of the ring and little fingers.

Flexor carpi ulnaris: Flexes and adducts the wrist.

The ulnar claw will develop as before, but with one key difference. The flexor digitorum profundus is paralysed, and there will not be any flexion at the distal IP joints of the ring and little fingers. Now the ulnar claw only consists of hyperextension at the MCP joints and flexion at the proximal IP joints. This produces a much less evident claw hand.

This is known as the ‘ulnar paradox‘ – you would expect a more debilitating injury to produce a more pronounced deformity, but in fact the opposite occurs.

Question 24

What is radial tunnel syndrome?

Answer 24

lateral forearm pain, may also have weakness secondary to pain (not nerve weakness, i.e not a PIN palsy

Same sites as PIN compression syndrome (5)

1. Leash of henry
2. fibrous bands from anterior to the radiocapitellar joint
3. medial edge ecrb
4. Leading edge supinator (Arcade of frohse)
5. distal edge supinator

Question 25

What are common sites of compression of the ulnar nerve when considering cubital tunnel syndrome?

Answer 25

From Proximal to distal. (* denotes most common)

1) Hypertrophied triceps
2) Medial intermuscular septum

3) *Arcade of Struthers (thickening of the deep investing fascia of the arm from medial triceps to the IM septum present in 70%, 1.5-2cm in width and 8-10cm proximal to the medial epicondyle)

4) *Cubital tunnel (btwn Osbornes ligament and MCL)

5) Anconeus epitrochlearis (accessory anconeus)

6) ***Btwn heads of FCU (most common)

7) Flexor/pronator aponeurosis (>5cm distal to medial epicondyle)

Question 26

What is Wartenberg syndrome?

What is another name for this?

Symptoms exacerbated with what motion?

What is the site of compression and how far from the styloid?
What are 3 differentials?

Answer 26

Aka Cheiralgia paraesthetica

Site: Compression of the superficial radial nerve where the nerve transitions from deep to superficial between ECRL and BR approximately 9cm from the styloid.

Exacerbated by pronation.

Differentials:

1) De Quervain’s
2) Lateral antebrachial Cutaneous nerve neuritis
3) intersection syndrome (Due to inflammation at crossing point of 1st dorsal compartment (APL and EPB ) and 2nd dorsal compartment (ECRL, ECRB))

Question 27

What are 5 causes of compression in Guyon’s canal?

Describe the zones of the GC?

Answer 27

compression in guyon’s canal due to:

1. ganglion (80%)
2. lipoma
3. repetative trauma
4. ulnar artery thrombosis or aneurysm
5. fracture/nonunion/malunion of the hook of hamate
6. pisiform dislocation
7. arthritis
8. palmaris brevis atrophy

symptoms related to location of lesion

Zone 1 - sensory and motor (ganglion and hook of hamate fractures top causes)

Zone 2 - motor only (ganglion and hook of hamate fractures top causes)

Zone 3 - sensory only (Ulnar artery thrombosis or aneurysm top cause)

Question 28

What 3 muscles in the extensor compartment does the PIN NOT innervate?

Answer 28

the mobile wad (innervated by radial nerve proper)

• ECRB (although this is variable)
• ECRL
• brachioradialis

Question 29

The ulnar nerve is (radial/ulnar) and (volar/dorsal) to the artery at the level of the wrist

Answer 29

Ulnar nerve is ulnar and dorsal to the artery at the level of the wrist

Question 30

What is Wartenberg’s sign?

Answer 30

Ulnar nerve injury - Ulnar drift of small finger due to unopposed function of EDM (radial) with paralysis of palmar interossei (ulnar)

EDM attaches ulnarly so will have an ulnar/abduction moment, pulling small finger ulnarly

vs: Wartenburg’s syndrome: superficial radial nerve injury

Question 31

What is the last mm innervated by:

• the Radial nerve proper
• PIN
• Median nerve proper
• AIN
• Ulnar

Answer 31

• Radial nerve proper - ECRL
• PIN - EIP
• Median - 2nd lumbrical (not the thenar eminence as this is from the recurrent branch which is given off more proximally)
• AIN - PQ
• Ulnar - Adductor pollicis (1st dorsal interossei is the last testable muscle innervated)

Question 32

What nerves branch off the ulnar nerve proximal to the elbow?

Answer 32

Usually none, but if any, are just articular branches

Question 33

What is the last muscle to be reinnervated after PIN injury? Bonus marks for full order of reinnervation.

Answer 33

Last to reinnervate: EIP

Order of reinnervation: Goes proximal to distal:

1. ECU
2. EDC
3. EDM
4. APL
5. EPL
6. EPB
7. EIP

Question 34

What are the nerve and muscle are involved with each of the following clinical scenarios?

• Wasting of infraspinatus
• Medial scapular winging
• Lateral scapular winging
• deltoid atrophy
• thenar atrophy

Answer 34

• wasting of infraspinatus - suprascapular nerve (in the spinoglenoid notch)
• medial winging - due to serratus anterior weakness (long thoracic nerve)
• lateral winging - due to weakness of trapezius (spinal accessory nerve) or rhomboids (dorsal scapular)
• deltoid atrophy - axillary
• thenar atrophy - recurrent branch of median nerve

Question 35

What is the most common nerve injury in a pediatric supracondylar fracture:

1) Flexion type
2) Extension type

?

Answer 35

1. Flexion Type - Ulnar Nerve
2. Extension type - AIN (radial second most common)

Question 36

What is the primary stabilizer of the extensor tendon at the MCP?

Secondary stabilizer?

Answer 36

Primary: Sagittal bands

Secondary: Juncturae tendinum

Question 37

Which of the following nerves have excellent recovery potential after grafting?

Moderate potential? Poor Potential?

Radial

Ulnar

Median

MSC

Tibial

Peroneal

Femoral

Answer 37

The following nerves had excellent recovery potential:

• radial
• musculocutaneous
• femoral

The following nerves had moderate recovery potential:

• median
• ulnar
• tibial

The following nerve had poor recovery potential:

• peroneal nerve

Difference in recovery potential of peripheral nerves after graft repairs.

Roganovic Z, Pavlicevic G
Neurosurgery. 2006 Sep;59(3):621-33;

Question 38

Which of the following is responsible for light touch?

1. Meissner’s corpuscles
2. Pacinian corpuscles
3. Merkel’s receptor
4. Ruffini corpuscles

Answer 38

Meissner corpuscle - a rapidly adapting sensory receptor, is very sensitive to touch.

Pacinian corpuscles are ovoid in shape, measuring approximately 1 mm in length. They respond to high-frequency vibration and rapid indentations of the skin.

Ruffini corpuscles are slowly adapting receptors that detect stretching of the skin.

Merkel’s skin receptors are slowly adapting skin receptors that detect pressure, texture, and low frequency vibration and can be appropriately evaluated by static two-point discrimination. Merkel’s disk receptors adapt slowly and sense sustained pressure, texture, and low-frequency vibrations.

Question 39

A 72-year-old female complains of progressive weakness with grasp and key pinch in her left hand. Physical exam of the hand is significant for decreased sensation on the volar aspect of the fourth and fifth digits. Dorsal sensation throughout the hand is normal. A clinical photo displaying bilateral key pinch is shown below. What is the most likely cause of compression?

1. Accessory head of the FPL
2. Flexor carpi ulnaris
3. Osborne’s ligament
4. Ganglion within Guyon’s canal
5. Anconeus epitrochlearis

Answer 39

Compression of the ulnar nerve within Guyon’s canal, termed ulnar tunnel syndrome, is most commonly caused by a ganglion cyst. A lack of dorsal ulnar sensory deficit helps differentiate entrapment here from at the elbow because the dorsal ulnar cutaneous nerve branches proximal to Guyon’s canal. The clinical photo demonstrates Froment’s sign where the FPL is used to substitute for the weakened adductor pollicis resulting in flexion of the thumb at the interphalangeal joint, and MCP joint hyperextension. The AIN can be compressed by the accessory head of the FPL (Gantzer’s muscle) which results in loss of FPL, index FDP and PQ motor function and no sensory deficits. Ulnar nerve compression at Osborne’s ligament, the two heads of the FCU, or by the anconeus epitrochlearis will classically result in volar and dorsal ulnar sensory loss of the affected hand.

Question 40

All of the following are possible sites of compression for the ulnar nerve EXCEPT:

1. arcade of Struthers
2. ligament of Struthers
3. flexor carpi ulnaris fascia
4. medial intermuscular septum
5. Osborne’s ligament

Answer 40

There are five sites of potential ulnar nerve entrapment around the elbow:

1. arcade of Struthers
2. medial intermuscular septum
3. medial epicondyle
4. cubital tunnel (osborne’s ligament)
5. deep flexor pronator aponeurosis.

The ulnar nerve emerges from the medial intermuscular septum, under the arcade of Struthers, and lies on the medial head of the triceps. At the level of the elbow, the ulnar nerve continues distally toward the posterior aspect of the condylar groove, passing between the medial epicondyle and olecranon to enter the cubital tunnel. The roof is formed by the arcuate (Osborne’s) ligament. This ligament blends distally with the antebrachial fascia superficial to the aponeurosis and connects the ulnar and humeral heads of the FCU.

The ligament of Struthers is a fibrous band extending from the supracondylar process of the humerus to the medial epicondyle which can cause compression of the median nerve.

Question 41

What are the preclavicular branches of the brachial plexus? What do they supply?

Answer 41

1. long thoracic nerve: serratus anterior
2. nerve to subclavius: subclavius
3. suprascapluar nerve: supraspinatus, infraspinatus
4. dorsal scapular nerve: rhomboids, levator scapulae

Question 42

Erb’s palsy: what is it, what are the muscles involved, what is the position of the arm, and is prognosis good/moderate/poor?

Answer 42

• upper trunk injury C5, C6.
• deltoid, rotator cuff, wrist extensors, elbow flexors
• get waiter’s tip position with shoulder adducted, elbow extended, wrist flexed
• good prognosis

Question 43

Klumpke’s palsy: what is it, what muscles involved, what arm position, and prognosis is good/moderate/bad?

Answer 43

• lower trunk injury C8, T1
• weakness of finger flexors, wrist flexors, hand intrinsics
• wrist extended, fingers flexed/clawed (loss of hand intrinsics)
• T1 involvement - can present with Horner’s syndrome
• prognosis is moderate/poor

Question 44

Why do you get a horner’s syndrome with Klumpke’s palsy?

Answer 44

the sympathetic outflow from the spinal cord is delivered via T1 to the stellate ganglia and the sympathetic chain which then distributes the fibers cephalad.

Question 45

total plexus palsy: what muscles affected, what arm position, and what is prognosis?

Answer 45

affects everything

supplied by brachial plexus

flaccid arm

worst prognosis

Biceps recovery at 3 months portends a better recovery

Question 46

describe the path of the axillary nerve after it leaves the brachial plexus

Answer 46

Off posterior cord

runs antero-inferior to subscap

passes through quadrangular space

wraps around surgical neck of humerus on underside of deltoid giving off 3 branches (5cm distal to lateral acromium):

anterior - wraps around surgical neck of humerus on undersurface of deltoid, supplying anterior deltoid

posterior - posterior branch supplies teres minor and posterior deltoid, then pierces the depe fascia and terminates as superior lateral cutaneous nerve of arm (seargent patch

articular branch - articular branch enters shoulder joint inferior to subscap

Question 47

describe the path of the radial nerve as it leaves the brachial plexus up to the elbow

Answer 47

• arises from posterior cord
• travels along anterior surface of posterior wall of axilla: on subscap and lat dorsi, teres major
• gives off 3 branches in axilla:

1. posterior cutaneous nerve of arm
2. branch to long head of triceps
3. branch to medial head of triceps

• goes through triangular INTERVAL (with profunda brachii a.)
• wraps around humerus shaft in the “spiral groove” from medial to lateral, deep to triceps in the groove
• it then gives off 4 in/after groove branches:

1. inferolateral (aka lower lateral in Gerwin approach article) cutaneous nerve of arm,
2. posterior cutaneous nerve of forearm,
3. branch to lateral head of triceps
4. branch to medial head of triceps and anconeus

• exits groove around 14cm proximal to lateral epicondyle
• pierces lateral intermuscular septum about 10cm proximal to trochlea surface (never less than 7.5cm)
• enters anterior compartment between lateral IM septum and brachialis
• emerges between BR and brachialis about 7.5cm proximal to trochlea (the joint), anterior to lateral epicondyle
• branches here to lateral brachialis, BR, ECRL
• stays deep to brachioradialis at elbow, divides into PIN and superficial branch… (continued in elbow section)

Question 48

Describe the path of the musculocutaneous nerve as it leaves the brachial plexus up to the elbow

Answer 48

• arises from lateral cord
• travels anteromedially on subscap (like the rest of the plexus branches) pierces conjoint tendon 5-8cm distal to coracoid
• runs between biceps and brachialis in the anterior compartment to enter the lateral aspect of the arm
• gives branch to biceps and brachialis
• a little above the elbow it pierces the deep fascia lateral to the tendon of the Biceps brachii
• emerges lateral to distal bicep tendon and brachoradialis to form lateral antebrachial cutaneous nerve

Question 49

describe the path of the ulnar nerve as it leaves the brachial plexus up to where it enters the elbow

Answer 49

• emerges from medial cord
• runs posterior-Medial to brachial artery in upper 1/2 of arm (medial nerve runs lateral)
• it pierces medial IM septum and runs just posterior to it
• deep to triceps at the arcade of struthers - 8cm from medial epicondyle
• passes into cubital tunnel posterior to medial epicondyle and enters forearm between heads of FCU…

Question 50

Describe the path of the median nerve as it leaves the brachial plexus up to when it enters the elbow

Answer 50

• emerges from plexus (from both medial and lateral cords)
• travels anteromedial to humerus
• travels LATERAL to brachial artery within anterior compartment
• crosses over artery before the elbow and then runs MEDIAL to brachial a.
• enters elbow medial to biceps, superficial to brachialis, and dives under lacertus, still MEDIAL to the artery

Question 51

What are the common sites of compression of the ulnar nerve?

Answer 51

Ligament of Struthers Arcade of Struthers

Hypertrophied medial triceps

Medial intermuscular septum

Osborne’s ligament

Anconeus epitrochlearis

Cubital tunnel 2 heads of FCU

Ligament of Spinner (aponeurosis between FDS of ring finger and humeral head of FCU)

Deep flexor pronator aponeurosis