Upper Limb Nerves Flashcards
What is Parsonage Turner syndrome?
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
Name the common sites of compression of the median nerve (5)?
What symptoms/signs will the patient have?
SPLAT for Median
- Supracondylar process, Ligament of Struthers
- Pronator teres (2 beads)
- Lacertus fibrosis
- FDS Aponeurosis
- Transverse Carpal Ligament (CTS no PCB deficit)
AIN:
Cannot make OK sign
- Gantzer Muscle ( acc. FPL)
- Enlarged biceps bursa
- 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)
- supracondylar process of the humerus
- ligament of struthers
- Lacertus fibrosis
- between ulnar and humeral heads of pronator
- FDS aponeurotic arch (sublimis bridge)
- (then in the wrist - carpal tunnel)
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?
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:
- edge of lacertus fibrosis
- tendinous edge of pronator teres
- FDS arch
- accessary head of FPL (Gantzers)
- accessory muscle from FDS to FDP
- Abberant mm (FCRB, palmaris profundus)
- thrombosed ulnar or radial artery
- abberant vessels
Answer from our lecture series:
- Accessory muscles: Gantzer’s accessory FPL muscle
- FDS
- Aberrant vessels
- Pronator teres
What are the common sites of compression of the Radial nerve (PIN compression syndrome)(5)?
FLEAS
- Fascial band at the radial head
- Recurrent Leash of Henry
- ECRB
- Arcade of Froshe (most common site, proximal edge of supinator)
- Supinator (distal edge)
Fibrous bands anterior to radial head
Recurrent radial vessels (Leash of Henry)
ECRB
Arcade of Frohse (proximal edge of supinator)
distal edge of supinator
What is the arcade of struthers?
What is the ligament of struthers?
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
What is Froment’s sign? What does it indicate?
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***
Describe the pathogenesis of ulnar claw:
- 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
What is the ulnar paradox?
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”
What is an anconeus epitrochlearis?
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”
What is pronator syndrome?
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
What is AIN syndrome?
Compression of AIN
Weakness of FPL, FDP to middle and index fingers, and PQ
Cannot make OK sign
When do you see the “Hand of Benediction”
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.
Where does the AIN originate?
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
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?
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!
What are the boundaries of the the radial tunnel?
Cubital tunnel?
Carpal Tunnel?
Guyon’s canal?
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
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?
- 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
What is the Martin Gruber Anastamosis?
What is it’s clinical significance?
Occurs in 10 to 44% of people
Branches from the median to ulnar nerve in the forearm. Can have 2 patterns:
- Median nn in the prox forearm to the ulnar nerve in the middle to distal third
- 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
What is the Marinacci Anastamosis?
- A reverse Martin gruber from the ulnar to the median nerve.
- THE ULNAR NERVE ENDS UP INNERVATING THE THENAR MUSCLES
What is the Riche-Cannieu Anastamosis?
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
Where does the AIN arise?
Where does it then run?
What does it innervate?
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)
What does Median nerve innervate in the forearm and hand and what is the order of supply?
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
What are 5 causes of compression in Guyon’s canal?
Describe the zones of the GC?
compression in guyon’s canal due to:
- ganglion (80%)
- lipoma
- repetative trauma
- ulnar artery thrombosis or aneurysm
- fracture/nonunion/malunion of the hook of hamate
- pisiform dislocation
- arthritis
- 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)
The ulnar nerve is (radial/ulnar) and (volar/dorsal) to the artery at the level of the wrist
Ulnar nerve is ulnar and dorsal to the artery at the level of the wrist
What is the last muscle to be reinnervated after PIN injury? Bonus marks for full order of reinnervation.
Last to reinnervate: EIP
Order of reinnervation: Goes proximal to distal:
- ECU
- EDC
- EDM
- APL
- EPL
- EPB
- EIP
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
- 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
What is the primary stabilizer of the extensor tendon at the MCP?
Secondary stabilizer?
Primary: Sagittal bands
Secondary: Juncturae tendinum
Which of the following is responsible for light touch?
- Meissner’s corpuscles
- Pacinian corpuscles
- Merkel’s receptor
- Ruffini corpuscles
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.
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?
- Accessory head of the FPL
- Flexor carpi ulnaris
- Osborne’s ligament
- Ganglion within Guyon’s canal
- Anconeus epitrochlearis
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.
All of the following are possible sites of compression for the ulnar nerve EXCEPT:
- arcade of Struthers
- ligament of Struthers
- flexor carpi ulnaris fascia
- medial intermuscular septum
- Osborne’s ligament
There are five sites of potential ulnar nerve entrapment around the elbow:
- arcade of Struthers
- medial intermuscular septum
- medial epicondyle
- cubital tunnel (osborne’s ligament)
- 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.
What are the preclavicular branches of the brachial plexus? What do they supply?
- long thoracic nerve: serratus anterior
- nerve to subclavius: subclavius
- suprascapluar nerve: supraspinatus, infraspinatus
- dorsal scapular nerve: rhomboids, levator scapulae
Erb’s palsy: what is it, what are the muscles involved, what is the position of the arm, and is prognosis good/moderate/poor?
- 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
Klumpke’s palsy: what is it, what muscles involved, what arm position, and prognosis is good/moderate/bad?
- 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
describe the path of the axillary nerve after it leaves the brachial plexus
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
Describe the path of the musculocutaneous nerve as it leaves the brachial plexus up to the elbow
- 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
describe the path of the ulnar nerve as it leaves the brachial plexus up to where it enters the elbow
- 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…
Describe the path of the median nerve as it leaves the brachial plexus up to when it enters the elbow
- 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
