Ch 5 - EDX: Upper Limb Mononeuropathy Flashcards
Describe the pathway of the median nerve in the upper arm.
Runs medial to the axillary artery, down the humerus and runs under the ligament of Struthers (LOS) at the medial epicondyle
What does the median nerve innervate in the forearm?
– Pronator teres (PT) – FCR – Palmaris longus – Flexor digitorum superficialis (FDS) – Palmar cutaneous branch – The AIN branches from the median nerve to innervate (four Ps): ■ Flexor pollicis longus (FPL) ■ Flexor digitorum profundus (FDP 1 and 2) ■ Pronator quadratus (PQ)
What does the median nerve innervate in the hand?
Through the carpal tunnel “LOAF” muscles: – Lumbricals (1, 2) – Opponens pollicis – Abductor pollicis brevis – Flexor pollicis brevis (superficial) – (Digital cutaneous branches)
What nerve and artery can be injured under the Ligament of Struthers (LOS)?
Median nerve and Brachial artery
What is the clinical presentation of nerve injury at the Ligament of Struthers?
Involvement of ALL median innervated muscles and loss of:
- Grip strength/ Benediction sign (FDS, FDP)
- Wrist flexion (FCR)
- Dull, aching in distal forearm
What is the bicipital aponeurosis?
Antebrachial fascia attaching biceps to the ulna
How can the median nerve be injured at the bicipital aponeurosis?
Entrapment or hematoma
compression resulting from an arterial blood gas or
venipuncture
What is pronator teres syndrome?
Median nerve compression between the heads of the PT muscle or the bridging fascial band of the FDS muscle
What is the clinical presentation of pronator teres syndrome?
All median innervated muscles EXCEPT PT involved
Dull ache of the proximal forearm exacerbated by forceful pronation (PT) or finger flexion (FDS). Forearm and hand muscles easily fatigued.
What is affected in AIN syndrome?
FPL, PQ, FDP 1, 2 weakness
The FPL is 1st muscle affected
What is the etiology of AIN syndrome?
Idiopathic process
Fracture of the forearm
Lacerations
Compression
What is the clinical presentation of AIN syndrome?
Pure motor syndrome
ABN “OK” sign
Difficulty forming a fist
What are the contents of the carpal tunnel?
Superficial layer -4 FDS tendons -1 FPL tendon -Median nerve -(FCR is outside the carpal tunnel) Deep layer -4 FDP tendons
What are different etiologies of carpal tunnel syndrome?
Inc canal volume: thyroid dz, CHF, renal failure, mass (tumor, hematoma), pregnancy (at 6 months and resolves postpartum).
Dec canal volume: fracture, arthritis, rheumatoid tenosynovitis.
Double crush syndrome: DM, cervical radiculopathy, TOS
Why are sensory NCS more sensitive than motor studies?
- Larger distribution of the large myelinated fibers, which are more susceptible to compression/ ischemia. - Antidromic studies produce larger amp
How does a demyelinating lesion in CTS present on EDX?
Slowing and prolongation of the distal motor and sensory latencies
How does a conduction block or axonal loss in CTS present on EDX?
Prolongation of the distal motor and sensory latencies
Dec distal CMAP and SNAP amp
How does CTS differ from peripheral neuropathy on EDX?
CTS: max slowing across the wrist
Peripheral neuropathy: distal segment more ABN
Describe EDX of mild CTS.
SNAP: Prolonged latency
CMAP: Normal
EMG: Normal
Describe EDX of moderate CTS.
SNAP: Prolonged latency, dec amp
CMAP: Prolonged latency
EMG: Normal
Describe EDX of severe CTS.
SNAP: absent
CMAP: Prolonged latency, dec amp
EMG: ABN activity
Describe the orthotic for mild CTS treatment.
Hand splint 0 to 30° neutral to extension
What are surgical indications for CTS?
Muscle atrophy
Severe pain
Severe median nerve damage
Profound muscle atrophy
What are indications of poor prognosis with CTS?
Sx > 10 mo Constant paresthesias \+ Phalen’s test < 10 sec Weakness, atrophy Prolonged latency on NCS ABN spontaneous activity
What is Martin-Gruber anastomosis?
AIN branch of the median nerve anastamose
w/ the ulnar nerve or proximal median nerve cross over to the ulnar nerve
What does Martin-Gruber anastomosis innervate?
ADP, ADM, and MC 1st DI muscles
How is Martin-Gruber anastomosis diagnosed on EDX?
Initial + deflection in CMAP and inc median amp at elbow but not at wrist
Artificially fast conduction velocity
What is a Riche-Cannieu anastomosis?
Connection of the recurrent branch of the median nerve in the hand to the deep motor branch of the ulnar nerve
What does Riche-Cannieu anastomosis produce?
All ulnar innervated hand
How is Riche-Cannieu anastomosis diagnosed on EDX?
Recording over the APB, CMAP waveform is absent w/ median nerve stim but present with ulnar nerve stim
Describe the pathway of the ulnar nerve in the upper arm
Medial surface of the medial head of the triceps, runs w/in
Arcade of Struthers (AOS), continues posteriorly in a sulcus b/w the medial epicondyle and olecranon called the retrocondylar groove
What is the Arcade of Struthers (AOS)?
Fascial band in the medial arm that connects the brachialis to the triceps brachii
What does the ulnar nerve innervate in the forearm?
Flexor carpi ulnaris (FCU) FDP Palmar ulnar cutaneous nerve Dorsal ulnar cutaneous (DUC) nerve Dorsal digital nerves
Why is the dorsal ulnar cutaneous nerve normal in ulnar neuropathies at the wrist?
Does not travel through Guyon’s canal (arising 5–8 cm more
proximally)
Describe how the ulnar nerve branches and what it innervates in the hand.
Superficial sensory branch Hypothenar branch – Opponens digiti quinti – Abductor digiti quinti – Flexor digiti quinti Deep motor branch – Palmaris brevis – 4 Dorsal interossei—(“DAB”: Abduction) – 3 Palmar interossei—(“PAD”: Adduction) – 2 Lumbricals – 1 Adductor pollicis – 1/2 Flexor pollicis brevis (deep head)
What is the clinical presentation of ulnar compression under Arcade of Struthers?
ALL ulnar innervated muscles
Radial deviation w/ wrist flexion
ABN ulnar sensation
Ulnar claw hand
Describe ulnar claw hand.
Hand at rest, an unopposed pull of EDC causes partial finger flexion of the fourth and fifth PIP and DIP joint due to
extension of the MCP
What is a positive Froment’s sign?
Inability to hold piece of paper with thumb and index finger due to adductor pollicis
weakness so pt substitutes FPL
What is a positive Wartenberg’s sign?
Inability to adduct the fifth digit (interossei weakness)
What is a tardy ulnar nerve palsy?
Ulnar neuropathy mos to yrs after a distal humeral fx d/t bone overgrowth, scar formation or inc carrying angle at elbow
What is the etiology of cubital tunnel syndrome?
Compression beneath the proximal edge of the FCU aponeurosis or arcuate ligament
What elbow angle should NCS done for accurate results?
90° to 110° elbow
flexion to avoid underestimation of actual nerve length, thus causing false
+ findings
When evaluating for cubital tunnel syndrome what is a benefit of recording at FDI instead of ADM?
FDI may show earlier abnormalities due to those nerve fascicles
being more prone to injury at the elbow
What can cause ulnar amp decrease above and below the elbow?
Martin-Gruber anastomosis
How can you check for Martin-Gruber anastomosis when evaluating the ulnar nerve with EDX?
Stim median nerve at the elbow will provide a waveform with an amp equal to what is considered “missing” from the ulnar nerve stim
What happens to CMAP in cubital tunnel syndrome?
~10 to 15 ms drop of CV across the elbow or a drop of amp of 20%
What is seen on EMG in cubital tunnel syndrome?
ABN activity in ulnar nerve hand intrinsics > forearm muscles
What is the most reliable muscle to test with EMG for cubital tunnel syndrome?
FDP has more fascicles that pass through the cubital tunnel and reliable than FCU
What is a Type I Shea classification?
Involvement of the deep ulnar branch, hypothenar, and sensory
What is a Type II Shea classification?
Involvement of deep ulnar motor branches
What is a Type III Shea classification?
Involvement of the superficial ulnar sensory branch
How can the ulnar nerve be injured at Guyon’s canal?
Cyclist’s palsy
Wrist ganglions
RA
What is the clinical presentation of ulnar injury at Guyon’s canal?
Painless wasting of the first DI
Claw hand (lumbrical
weakness)
FDP remains intact, causing marked finger flexion
Describe which SNAP’s are ABN in ulnar injury at Guyon’s canal.
- DUC nerve spared
- SNAP to 5th digit ABN
Describe the Radial nerve course in the upper arm
Located posterior to the axillary artery.
Descends b/w the long and medial heads of the triceps muscle toward the spiral groove.
Which muscles are innervated by the Radial nerve ABOVE the spiral groove?
Triceps brachii
Anconeus
Posterior cutaneous nerve
Lower lateral cutaneous nerve
Which muscles are innervated by the Radial nerve BELOW the spiral groove?
Brachioradialis (BR)
Extensor carpi radialis longus (ECR-L)
Posterior cutaneous nerve of forearm
Describe the course of the Radial nerve 10 cm proximal to the lateral epicondyle of the humerus.
Pierces the lateral intermuscular septum and enters the anterior compartment of the arm. Continues distally b/w the brachioradialis and brachialis
What does the Radial nerve split into at the lateral epicondyle?
Motor (posterior interosseus nerve [PIN]) Sensory branch (superficial radial nerve)
Which muscles do the PIN innervate?
– Extensor carpi radialis brevis (ECR-B) – Supinator – Extensor digitorum communis (EDC) – Extensor digiti minimi (EDM) – Extensor carpi ulnaris (ECU) – Abductor pollicis longus (APL) – Extensor pollicis longus (EPL) – Extensor pollicis brevis (EPB) – Extensor indicis proprius (EIP)
What is the clinical presentation of crutch palsy?
Weakness in all radial nerve innervated muscles, including the triceps brachii. Sensation may be decreased over the posterior arm and forearm
What are etiologies of Radial nerve injury at the spiral groove?
Prolonged arm position over back of chair or person’s head.
Humerus fracture at spiral groove
Which muscles are spared in Radial nerve spiral groove injury?
Triceps brachii and Anconeus
What is the clinical presentation of Radial nerve spiral groove injury?
Weakness in EF, supination, wrist drop and finger extension. Sensory deficits in dorsal aspect of hand and posterior forearm
What is Radial tunnel syndrome?
Radial nerve or PIN can be entrapped b/w the brachialis and BR
How are Radial tunnel syndrome symptoms reproduced?
Resisted extension of the 3rd digit during elbow extension
Resisted supination
Palpation of the radial head
What are etiologies of PIN syndrome?
Compression of the nerve at the Arcade of Frohse of the supinator Lipoma Ganglion cyst Synovitis from RA Monteggia fx
What is a Monteggia fracture?
Fracture of the proximal 1/3 of the ulna and dislocation of the radial head
What is the etiology of a Monteggia fracture?
FOOSH w/ the forearm locked in full pronation
What is the clinical presentation of PIN syndrome?
Pseudo claw-hand deformity may be demonstrated (finger extensor weakness). Radial deviation is noted with wrist extension (ECU weakness) and sensation is spared
What is Cheiralgia paresthetica?
Superficial radial neuropathy or Wristwatch syndrome
What is the clinical presentation of Superficial radial neuropathy?
Pure sensory syndrome on the dorsal radial aspect of the hand
How can symptoms of Superficial radial neuropathy be exacerbated?
Palmar and ulnar wrist flexion or forced pronation
Describe the course of the musculocutaneous nerve in the arm.
Passes along the medial aspect of the
humerus and continues anterior to the antecubital fossa, lateral to the biceps tendon
What does the musculocutaneous nerve innervate?
– Coracobrachialis
– Biceps brachii
– Brachialis
–Lateral antebrachial cutaneous nerve
What are etiologies of musculocutaneous injury?
Entrapment from the coracobrachialis Gunshot wounds
Shoulder dislocation
Phlebotomy
What is the clinical presentation of musculocutaneous injury?
EF weakness
ABN sensation over lateral forearm
Coracocbrachialis usually spared
What are the borders of the quadrangular space?
Humerus
Long head of triceps
Teres minor
Teres major
Describe the course of the axillary nerve.
Runs through the quadrangular space
What are etiologies of Axillary neuropathy?
Traction or compression from a shoulder dislocation
Humeral
head fracture
Improper axillary crutch use
What is the clinical presentation of Axillary neuropathy?
Shoulder flexion and abduction weakness (deltoid) ER weakness (teres minor) ABN sensation of lateral shoulder
Describe the course of the Suprascapular nerve.
Passes posterior triangle of the neck, runs beneath trapezius to superior scapula through suprascapular notch then around spinoglenoid notch
What is the MC nerve involved in neuralgic amyotrophy?
Suprascapular nerve
What are etiologies of suprascapular neuropathy?
Forced scapular protraction Penetrating wounds Improper crutch use Traction rotatorcuff rupture Erb’s palsy Spinoglenoid ganglions Hematoma Suprascapular or spinoglenoid notch entrapment Paralabral cyst Overhead activities
What is the clinical presentation of suprascapular neuropathy?
Weakness in abduction (SS) and external rotation (IS) of the glenohumeral joint
Describe the course of the long thoracic nerve.
Runs distally along the thoracic wall to innervate the serratus anterior
What is weak/injured in medial scapula winging?
Serratus anterior weakness
Long thoracic nerve injury
What is weak/injured in lateral scapula winging?
Tapezius weakness
Spinal accessory nerve injury
What are etiologies of long thoracic nerve injury?
Fall
MVA
Sports activities
Shoulder bags
