Week 5 - Nerve Injuries Flashcards by Joseph Glenn

What is radiculopathy?

Nerve root(s) damaged

Affects dermatome & myotome, and might affect several peripheral nerves.

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What is the main characteristic of neuropathy?

Peripheral nerve(s) damaged

Severely affects skin/muscles innervated by the nerve distal to injury.

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What is an example of radiculopathy?

C8 Radiculopathy

C8 contributes to ulnar, median & radial nerves, leading to partial weakness of muscles supplied by those nerves.

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What occurs in ulnar nerve neuropathy?

Weakness (often complete paralysis) of muscles & skin innervated solely by ulnar nerve

This results in significant functional impairment.

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What distinguishes dermatome issues from cutaneous nerve distribution issues?

Dermatome issue indicates a CNS/spinal nerve issue
Cutaneous nerve distribution indicates a peripheral nerve issue

This is due to the mixing of nerve fibers in the brachial plexus.

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Who developed the original dermatome maps?

Foerster, 1933

Based on dissection, shingles distribution, and rhizotomy.

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What was the basis for the ‘new’ dermatome maps by Keegan & Garrett in 1948?

Hypoalgesia due to herniated IV disc and anaesthesia

Issues include the subjective nature of sensory-based methods and overlap of dermatomes.

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What are the three classifications of peripheral neuropathy according to Seddon?

I: Neurapraxia
II: Axonotmesis
III: Neurotmesis

Each classification varies based on severity and recovery potential.

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What is neurapraxia?

Temporary loss in function with recovery in <12 weeks

Caused by mild injury, toxins, or compression ischaemia.

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What happens in axonotmesis?

Axon & myelin sheath locally destroyed, with Wallerian degeneration distal to injury

Schwann cells clear myelin and guide regenerating axons.

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What is the most severe classification of peripheral nerve injury?

Neurotmesis

Often requires surgery for recovery.

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What are the five grades of Sunderland’s classification of peripheral nerve injury?

I: Neurapraxia
II: Axonotmesis
III: Endoneurium only
IV: Endoneurium & Perineurium
V: Endoneurium, Perineurium & Epineurium

This classification helps to assess the severity of nerve injuries.

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What are the roots of the Brachial Plexus?

C5, C6, C7, C8, T1

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What mnemonic can help remember the roots that contribute to proximal nerves?

Read: Roots (C5-T1)
That: Trunks (Superior, Middle, Inferior)
Damn: Divisions (Anterior, Posterior)
Cadaver: Cords (Lateral, Medial, Posterior)
Book: Branches (e.g., radial, ulnar, median, etc.)

Upper roots contribute more to proximal nerves

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What is the mnemonic for the Musculocutaneous nerve?

3 Muskateers – C5, C6, C7

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Which roots are involved in the Upper Plexus Injury (Erb-Duchenne Palsy)?

C5, C6 (7)

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What is a characteristic posture of the arm in Upper Brachial Plexus Injury?

Arm adducted & medially rotated

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What is the characteristic hand position in Lower Brachial Plexus Injury (Klumpke’s Palsy)?

Total claw hand & ape hand

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What percentage of neonatal brachial plexus injury cases involve C5 and C6?

50%

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What is the risk factor associated with neonatal brachial plexus injury?

Shoulder dystocia

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What happens to the forearm in Erb’s Palsy plus (C5-7)?

Forearm is extended & pronated
Wrist & fingers flexed

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What is the term for the paralysis of the hand associated with C8 and T1 injuries?

Klumpke’s

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What is Horner’s Syndrome associated with?

Damage to T1

What is the outcome for most cases of neonatal brachial plexus injury?

Most recover spontaneously

What is a common surgical intervention for persistent impairment in brachial plexus injuries?

- Contracture release - Tendon-transfer - Nerve-transfer surgery

True or False: The lower roots contribute more to proximal nerves.

False

Fill in the blank: The mnemonic for the Radial nerve is _______.

Five RATS – C5, C6, C7, C8, T1

What is the characteristic function loss in Upper Brachial Plexus Injury?

Reduction/loss of function of muscles innervated by C5, 6 fibres

What are the main affected muscles in Erb’s Palsy?

- Deltoid, - Infraspinatus - biceps

What is the incidence rate of neonatal brachial plexus injury?

1/666 live births

What is the route of the Axillary Nerve?

1. Runs posteriorly 2. Medial to humeral neck to enter the Quadrangular space ## Footnote Supplies the deltoid, teres minor, and skin of the 'regimental badge area' of the shoulder.

What are the common mechanisms of injury for the Axillary Nerve?

* Shoulder dislocation * Humeral fracture * Sleeping with arms above head

What symptoms are associated with Axillary Nerve injury?

* Difficulty abducting & laterally rotating arm * Numbness of superolateral arm * Eventually atrophy of deltoid

What is the route of the Musculocutaneous Nerve?

1. Pierces coracobrachialis 2. Runs between brachialis & biceps 3. Becomes superficial lateral to biceps tendon

What muscles does the Musculocutaneous Nerve supply?

* Biceps * Brachialis * Coracobrachialis

What are the mechanisms of injury for the Musculocutaneous Nerve?

* Direct trauma in axilla * Shoulder dislocation * Overuse of anterior arm muscles * Iatrogenic

What are the symptoms of Musculocutaneous Nerve injury?

* Numbness of lateral forearm * Weakened elbow flexion

What is the route of the Radial Nerve?

1. Exits axilla via Triangular interval 2. Spirals around humerus between lateral & medial heads of triceps in Radial groove

What muscles does the Radial Nerve supply?

* Long & lateral heads of triceps * Brachioradialis * Extensor carpi radialis longus (ECRL) * Extensor carpi radialis brevis (ECRB)

What are the mechanisms of injury for the Radial Nerve?

* Fracture of humeral shaft * Compression against humerus in spiral groove * Crutch paralysis

What are the symptoms of Radial Nerve injury in the Spiral Groove?

* Weak wrist & MCP extension (wrist drop) * Numb dorsal hand/forearm * Difficulty making a fist

What can cause injury to the Deep Branch of the Radial Nerve?

* Fracture of proximal radius * Radial head dislocation * Repetitive pronation/supination

What are the symptoms of Deep Branch Radial Nerve injury?

* Weak MCP extension & grip * No sensory loss * No deficits in elbow extension

What is Wartenberg’s Syndrome?

Injury to Superficial Branch of Radial Nerve ## Footnote Mechanisms include trauma, laceration, or compression.

What are the symptoms of Superficial Branch of Radial Nerve injury?

Paraesthesias of dorsolateral hand/forearm

What is the route of the Median Nerve?

1. Runs through cubital fossa deep to bicipital aponeurosis 2. Passes between the 2 heads of pronator teres

What muscles does the Median Nerve supply?

* Most of the anterior forearm (except FCU & Medial ½ of FDP) * Thenar muscles * Lumbricals 1 & 2 ## Footnote (Flexor Digitorum Profundus)

What are the common mechanisms of injury for the Median Nerve?

* Supracondylar humeral fracture * Laceration at wrist * Carpal tunnel syndrome

What are the symptoms of Median Nerve injury?

* Weak wrist flexion with ulnar deviation * Cannot pronate * Weak/no MCP/IP flexion of digits 1-3 * 'Hand of Benediction'

What is the presentation of Anterior Interosseous Nerve injury?

No sensory deficit, but forearm pain and inability to make an 'OK hand sign'

What is the route of the Ulnar Nerve?

1. Pierces medial intermuscular septum & runs posterior to medial epicondyle 2. enters cubital tunnel

What are the common mechanisms of Ulnar Nerve injury?

* Compression in cubital tunnel * Guyon’s (Ulnar) canal * Arthritis

What are the symptoms of Ulnar Nerve injury?

* Weak wrist flexion with radial deviation * Loss of DIP flexion of digits 4 & 5 * Claw hand * Paraesthesia of palmar & dorsal medial hand

What is Froment’s Sign/Test?

Test for Ulnar Nerve injury, where adductor pollicis is paralyzed

What happens in Long Thoracic Nerve Damage?

Medial border of scapula pulls away from ribcage due to weakening of Serratus anterior | Winged Scapula

What is the usual treatment for Long Thoracic Nerve Damage?

Most heal with conservative treatment, surgery may involve transferring Pec. Major tendon to inferior scapula