Weekly Check Point - Nerve Injury & Impingement Flashcards
A 25-year-old construction worker presents with wrist drop and inability to extend the fingers after a humeral shaft fracture.
Which nerve is most likely injured?
A. Median Nerve
B. Radial Nerve
C. Axillary Nerve
D. Ulnar Nerve
B. Radial Nerve
Feedback:
Based on answering correctly
The radial nerve is most susceptible to injury in mid-shaft humeral fractures due to its close proximity to the spiral groove. A wrist drop (inability to extend the wrist and fingers) is the classic presentation. The median nerve (A) controls thumb opposition and finger flexion, the ulnar nerve (B) affects intrinsic hand muscles (claw hand), and the axillary nerve (D) innervates the deltoid.
Which of the following is the earliest pathological event in Wallerian degeneration following peripheral nerve transection?
A. Schwann cell proliferation
B. Calcium influx and activation of degradative enzymes
C. Myelin phagocytosis
D. Macrophage infiltration
B. Calcium influx and activation of degradative enzymes
Feedback:
Based on answering correctly
Wallerian degeneration begins within 24–72 hours with calcium influx, triggering enzymatic breakdown of neurofilaments and microtubules (Page 16).
Macrophage infiltration (A) and myelin phagocytosis (D) occur later (days to weeks).
Schwann cell proliferation (C) supports regeneration but is not the initial event.
A patient with carpal tunnel syndrome reports worsening nocturnal paresthesia in the thumb, index, and middle fingers.
Which maneuver will most likely reproduce symptoms?
A. Adson’s test
B. Phalen’s test
C. Froment’s sign
D. Tinel’s sign
B. Phalen’s test
Feedback:
Based on answering correctly
Phalen’s test (holding wrist in flexion for 60 seconds) increases pressure in the carpal tunnel, reproducing median nerve paresthesia. Tinel’s sign (C) (tapping over the nerve) may also elicit symptoms but is less specific. Froment’s sign (A) tests ulnar nerve function (thumb adduction weakness), and Adson’s test (D) assesses thoracic outlet syndrome.
A motorcyclist sustains a brachial plexus injury after a high-impact collision. On exam, he has a medially rotated arm with loss of shoulder abduction and deltoid paralysis.
Which nerve root is most likely affected?
A. C7
B. C8 - T1
C. C5
D. C5 - C6
D. C5 - C6
Feedback:
Based on answering correctly
The upper trunk (C5-C6) is commonly injured in Erb’s palsy (e.g., motorcycle accidents), leading to waiter’s tip posture (arm adducted, medially rotated, elbow extended). Deltoid paralysis (axillary nerve, C5) and shoulder abduction loss (suprascapular nerve, C5-C6) are key findings. C8-T1 (C) causes Klumpke’s palsy (claw hand).
A 30-year-old patient presents with weakness and sensory loss in the right hand after a deep laceration to the wrist.
Which is the most appropriate initial diagnostic test?
A. Nerve conduction studies (NCS)
B. MRI of the brachial plexus
C. Electromyography (EMG)
D. X-ray of the wrist
A. Nerve conduction studies (NCS)
Feedback:
Based on answering correctly
NCS is the first-line test for suspected peripheral nerve injury, as it assesses nerve function (conduction block, demyelination, or axonal loss).
EMG (A) evaluates muscle denervation but is typically done after NCS (usually 3–4 weeks post-injury).
MRI (C) is useful for structural lesions (e.g., brachial plexus trauma) but not the initial test.
X-ray (D) may detect fractures but does not assess nerve integrity.
A patient with diabetes presents with foot drop and sensory loss over the dorsum of the foot.
Which nerve is most commonly impinged at the fibular head?
A. Saphenous nerve
B. Common peroneal nerve
C. Tibial nerve
D. Sural nerve
B. Common peroneal nerve
Feedback:
Based on answering correctly
The common peroneal nerve is vulnerable to compression at the fibular head, causing foot drop and dorsal foot sensory loss (Page 45).
Tibial nerve (A) compression occurs in tarsal tunnel syndrome.
Sural (C) and saphenous (D) nerves are sensory-only branches.
A baseball pitcher develops medial elbow pain and numbness in the ring and little fingers.
Which anatomical structure is most likely compressing the affected nerve?
A. Cubital tunnel retinaculum
B. Inguinal ligament
C. Supinator muscle
D. Flexor retinaculum
A. Cubital tunnel retinaculum
Feedback:
Based on answering correctly
Ulnar nerve compression at the cubital tunnel (elbow) causes medial elbow pain and sensory loss in ulnar distribution (Page 44).
Supinator (A) compresses the posterior interosseous nerve (radial nerve branch).
Flexor retinaculum (C) is involved in carpal tunnel syndrome.
Inguinal ligament (D) compresses the lateral femoral cutaneous nerve.
A construction worker with forearm pain has weakness in thumb/index finger flexion and numbness over the thenar eminence. Pronation remains intact.
Where is the nerve most likely compressed?
A. Pronator teres
B. Arcade of Struthers
C. Carpal tunnel
D. Spinoglenoid notch
A. Pronator teres
Feedback:
Based on answering correctly
Pronator teres syndrome (median nerve compression in forearm) spares pronation (innervated proximal to compression) but affects flexor pollicis longus and palmar cutaneous branch (thenar eminence sensation) (Page 44).
Carpal tunnel (A) spares forearm pain and palmar cutaneous branch.
Arcade of Struthers (C) compresses the ulnar nerve.
Spinoglenoid notch (D) affects the suprascapular nerve.
A 50-year-old typist complains of nocturnal tingling in her thumb, index, and middle fingers, along with weakness when opening jars. Physical exam reveals a positive Tinel’s sign at the wrist.
What is the most likely site of nerve impingement?
A. Guyon’s canal
B. Cubital tunnel
C. Carpal tunnel
D. Pronator teres
C. Carpal tunnel
Feedback:
Based on answering correctly
Classic carpal tunnel syndrome symptoms (nocturnal paresthesia in median nerve distribution + weakness in thumb opposition) with Tinel’s sign at the wrist localize compression to the transverse carpal ligament (Page 44).
Pronator teres (A) affects the median nerve proximally (no nocturnal symptoms).
Cubital tunnel (C) compresses the ulnar nerve (little/ring finger symptoms).
Guyon’s canal (D) causes pure ulnar neuropathy.
Which of the following is the strongest risk factor for developing carpal tunnel syndrome?
A. Tall stature
B. Vitamin D deficiency
C. Repetitive hand use
D. Male Gender
C. Repetitive hand use
Feedback:
Based on answering correctly
Repetitive flexion/extension (typing, manual labor) is the most modifiable risk factor.
CTS is more common in females (A).
Height (C) and vitamin D (D) are not established risks.
