Multiple-choice clinical situations focused on anatomy, with explanations:
Clinical Scenario: Brachial Plexus Injury
A 25-year-old male presents to the emergency department after falling off his motorcycle and landing on his right shoulder. He reports numbness and weakness in his right arm. On examination, the patient has difficulty abducting his arm beyond 30 degrees and cannot flex his elbow. There is also diminished sensation over the lateral aspect of his forearm.
Question: What part of the brachial plexus is most likely injured?
A) C5-C6 Roots
B) C8-T1 Roots
C) Posterior Cord
D) Medial Cord
E) Long Thoracic Nerve
Answer: A) C5-C6 Roots
Explanation: The clinical presentation suggests an upper trunk (Erb-Duchenne) brachial plexus injury, which typically affects the C5 and C6 nerve roots. This injury leads to weakness in muscles innervated by these roots, including the deltoid (abduction of the arm), biceps (elbow flexion), and brachialis. The sensory deficit over the lateral aspect of the forearm is consistent with damage to the lateral cutaneous nerve of the forearm, derived from C5-C6.
Clinical Scenario: Ulnar Nerve Entrapment
A 40-year-old office worker presents with numbness and tingling in his right hand. He reports difficulty gripping objects and says his symptoms worsen when he leans on his elbows. On physical exam, you note weakness in the intrinsic muscles of the hand and a positive Froment’s sign. The sensory examination reveals loss of sensation over the medial side of the hand, including the fifth digit.
Question: Where is the likely site of ulnar nerve entrapment?
A) Cubital Tunnel
B) Guyon’s Canal
C) Carpal Tunnel
D) Axilla
E) Radial Tunnel
Answer: A) Cubital Tunnel
Explanation: The symptoms described—numbness in the medial side of the hand, weakness in the intrinsic hand muscles, and exacerbation of symptoms when leaning on the elbow—are consistent with ulnar nerve entrapment at the cubital tunnel. The cubital tunnel is located at the elbow, and compression of the ulnar nerve here can lead to sensory loss and motor weakness in the distribution of the ulnar nerve.
Clinical Scenario: Herniated Disc
A 55-year-old man presents with severe low back pain radiating down his left leg to the lateral side of his foot. He reports difficulty walking and describes weakness in dorsiflexing his left foot. On examination, there is decreased strength in foot dorsiflexion and an absent Achilles reflex.
Question: Which nerve root is most likely compressed?
A) L3
B) L4
C) L5
D) S1
E) S2
Answer: D) S1
Explanation: This patient's symptoms suggest a herniated disc compressing the S1 nerve root, as indicated by the pain radiating to the lateral foot, weakness in dorsiflexion, and an absent Achilles reflex. Compression of the S1 nerve root often causes these specific deficits, including weakness in the gastrocnemius-soleus complex, which is involved in plantarflexion of the foot, and decreased Achilles reflex.
Clinical Scenario: Femoral Nerve Injury
A 30-year-old man is recovering from surgery for a retroperitoneal mass. Postoperatively, he complains of difficulty walking and knee instability. On examination, there is weakness in extending the knee and loss of sensation over the anterior thigh and medial leg.
Question: Which nerve is most likely affected?
A) Obturator nerve
B) Femoral nerve
C) Sciatic nerve
D) Tibial nerve
E) Common peroneal nerve
Answer: B) Femoral nerve
Explanation: The femoral nerve (L2-L4) is responsible for innervating the quadriceps muscles, which extend the knee. Injury to this nerve leads to weakness in knee extension and loss of sensation over the anterior thigh and medial leg (supplied by the saphenous nerve, a branch of the femoral nerve). The clinical presentation suggests damage to the femoral nerve, possibly due to its proximity to the retroperitoneum during surgery.
Clinical Scenario: Median Nerve Injury
A 28-year-old woman is seen after a car accident in which she sustained a laceration to her forearm. She complains of weakness when attempting to make a fist, and her thumb remains extended and abducted. On examination, you note weakness in thumb opposition and loss of sensation in the lateral three and a half digits.
Question: Which nerve is injured?
A) Radial nerve
B) Ulnar nerve
C) Median nerve
D) Axillary nerve
E) Musculocutaneous nerve
Answer: C) Median nerve
Explanation: The median nerve is crucial for thumb opposition and for making a fist. Injury to the median nerve leads to weakness in thumb opposition and sensory loss in the lateral three and a half digits (palmar side). The fact that the thumb remains extended and abducted suggests paralysis of the thenar muscles, which are innervated by the median nerve.
Brachial Plexus Injury
A 32-year-old male presents to the emergency department after a fall from his bike onto his right shoulder. He is unable to abduct his right arm and has a "waiter's tip" deformity. Sensation is diminished over the lateral aspect of the shoulder.
Question: What part of the brachial plexus is most likely injured?
A) C5-C6 roots
B) C7 root
C) C8-T1 roots
D) Posterior cord
E) Medial cord
Answer: A) C5-C6 roots
Explanation: This patient presents with classic Erb-Duchenne palsy, which involves injury to the upper trunk of the brachial plexus (C5-C6 roots). The "waiter's tip" position is due to the paralysis of the shoulder abductors (deltoid and supraspinatus) and elbow flexors (biceps brachii). The sensory loss over the lateral shoulder also correlates with C5-C6 involvement.
Radial Nerve Palsy
A 45-year-old woman comes to the clinic complaining of weakness in her right hand and wrist. She recently slept with her arm over a chair during a long flight. On exam, she has wrist drop and decreased sensation over the dorsal surface of the hand. She can still extend her elbow.
Question: Which nerve is most likely affected?
A) Axillary nerve
B) Ulnar nerve
C) Radial nerve
D) Median nerve
E) Musculocutaneous nerve
Answer: C) Radial nerve
Explanation: Radial nerve palsy typically presents as "wrist drop," which is caused by weakness in the wrist extensors. The nerve can be compressed at the mid-shaft of the humerus, often due to prolonged pressure (e.g., "Saturday night palsy" or falling asleep on the arm). The ability to extend the elbow is preserved because the nerve branches supplying the triceps are proximal to the lesion.
Femoral Nerve Injury
A 50-year-old male is recovering from surgery for a large retroperitoneal tumour. After surgery, he reports difficulty walking and notes that his knee feels unstable. On exam, you note weakness in knee extension and decreased sensation over the anterior thigh and medial leg.
Question: Which nerve is most likely affected?
A) Obturator nerve
B) Femoral nerve
C) Sciatic nerve
D) Tibial nerve
E) Common peroneal nerve
Answer: B) Femoral nerve
Explanation: The femoral nerve innervates the quadriceps muscle, which is responsible for knee extension. Injury to the femoral nerve can occur during retroperitoneal surgeries. Sensory loss over the anterior thigh and medial leg is due to involvement of the saphenous nerve, a branch of the femoral nerve.
Median Nerve Injury
A 29-year-old woman cuts her wrist deeply while preparing dinner. She reports numbness in her thumb, index, and middle fingers and difficulty grasping objects. On exam, she has weakness in thumb opposition.
Question: Which nerve is likely injured?
A) Radial nerve
B) Ulnar nerve
C) Median nerve
D) Axillary nerve
E) Musculocutaneous nerve
Answer: C) Median nerve
Explanation: The median nerve controls thumb opposition and sensation over the lateral three and a half fingers. Injury to this nerve at the wrist (e.g., in a laceration) leads to loss of thumb opposition and sensory loss in the same distribution.
Sciatic Nerve Injury
A 40-year-old man presents after a gluteal injection given several weeks ago. He complains of weakness in his leg and difficulty walking. On exam, you notice weakness in knee flexion, ankle dorsiflexion, and decreased sensation on the lateral aspect of his foot.
Question: Which nerve is likely affected?
A) Femoral nerve
B) Obturator nerve
C) Sciatic nerve
D) Tibial nerve
E) Common peroneal nerve
Answer: C) Sciatic nerve
Explanation: The sciatic nerve innervates the muscles responsible for knee flexion and ankle dorsiflexion and provides sensory innervation to the lateral foot. It is often injured by improperly placed intramuscular injections in the gluteal region.
Carpal Tunnel Syndrome
A 38-year-old woman who works as a typist presents with numbness and tingling in her thumb, index, and middle fingers, especially at night. She reports that shaking her hands relieves the symptoms. On physical exam, there is weakness in thumb opposition.
Question: What structure is compressing the nerve?
A) Palmar carpal ligament
B) Flexor retinaculum
C) Extensor retinaculum
D) Annular ligament
E) Guyon’s canal
Answer: B) Flexor retinaculum
Explanation: In carpal tunnel syndrome, the median nerve is compressed under the flexor retinaculum (transverse carpal ligament). The patient presents with classic symptoms, including nocturnal hand paresthesia and weakness in thumb opposition.
Common Peroneal Nerve Injury
A 35-year-old man presents after a fracture of the fibular neck. He complains of difficulty walking and states that his foot drags when he tries to take a step. On exam, he has a foot drop and sensory loss over the dorsum of his foot.
Question: Which nerve is likely injured?
A) Tibial nerve
B) Common peroneal nerve
C) Femoral nerve
D) Sural nerve
E) Saphenous nerve
Answer: B) Common peroneal nerve
Explanation: The common peroneal nerve winds around the neck of the fibula, making it vulnerable to injury. Foot drop is caused by paralysis of the dorsiflexors of the foot (innervated by the deep peroneal nerve, a branch of the common peroneal nerve).
Knee Injury – ACL Tear
A 25-year-old male presents to the emergency department after twisting his knee while playing soccer. He describes hearing a "pop" and feeling immediate swelling. On physical examination, you note a positive Lachman test.
Question: Which structure is most likely injured?
A) Anterior cruciate ligament (ACL)
B) Medial collateral ligament (MCL)
C) Lateral collateral ligament (LCL)
D) Posterior cruciate ligament (PCL)
E) Patellar tendon
Answer: A) Anterior cruciate ligament (ACL)
Explanation: A positive Lachman test (increased anterior translation of the tibia relative to the femur) is highly suggestive of an ACL tear, which is common in twisting injuries, especially in athletes. The "pop" and rapid onset of swelling further support this diagnosis.
Medial Collateral Ligament Injury
A 30-year-old man is brought to the clinic after a skiing accident. He complains of pain along the inner aspect of his knee and swelling. Examination reveals joint instability with valgus stress.
Question: Which structure is most likely injured?
A) Anterior cruciate ligament (ACL)
B) Medial collateral ligament (MCL)
C) Lateral collateral ligament (LCL)
D) Meniscus
E) Patellar ligament
Answer: B) Medial collateral ligament (MCL)
Explanation: MCL injury is often caused by trauma to the lateral side of the knee, leading to a valgus deformity (inward collapse). A positive valgus stress test confirms MCL injury, which affects the stabilizing structures on the medial side of the knee.
Meniscal Tear
A 40-year-old man presents with knee pain after twisting his knee while playing basketball. He reports difficulty fully extending his knee, and during the physical exam, you note a positive McMurray’s test with an audible click during knee flexion and extension.
Question: What structure is most likely damaged?
A) ACL
B) PCL
C) Lateral meniscus
D) Medial meniscus
E) Patellar tendon
Answer: D) Medial meniscus
Explanation: A positive McMurray’s test with clicking indicates a meniscal tear, particularly the medial meniscus, which is more commonly injured. Meniscal tears often result from twisting movements, and patients may experience locking or clicking of the knee.
Hip Dislocation
A 34-year-old male is brought to the emergency room after a motor vehicle collision. His right leg is shortened, adducted, and internally rotated. He is unable to move his leg due to pain.
Question: What is the most likely injury?
A) Anterior hip dislocation
B) Posterior hip dislocation
C) Femoral neck fracture
D) Acetabular fracture
E) Intertrochanteric femur fracture
Answer: B) Posterior hip dislocation
Explanation: In posterior hip dislocation, the affected leg is typically shortened, adducted, and internally rotated. This type of injury is common in motor vehicle accidents where the knee is driven into the dashboard. Posterior dislocations require urgent reduction to prevent complications such as avascular necrosis of the femoral head.
Femoral Neck Fracture
A 72-year-old woman falls at home and presents with severe pain in her left hip. Her left leg appears shortened and externally rotated. She is unable to bear weight on the affected side.
Question: What is the most likely diagnosis?
A) Intertrochanteric femur fracture
B) Posterior hip dislocation
C) Femoral neck fracture
D) Pelvic fracture
E) Acetabular fracture
Answer: C) Femoral neck fracture
Explanation: A femoral neck fracture is common in elderly patients after a fall, particularly in those with osteoporosis. The affected leg is typically shortened and externally rotated, distinguishing it from hip dislocations where the leg is often internally rotated.
Patellar Dislocation
A 19-year-old female athlete presents with sudden onset knee pain after a twisting injury while running. Her knee is visibly deformed, and her patella appears displaced laterally. She is unable to extend her knee.
Question: What is the most likely injury?
A) ACL tear
B) MCL tear
C) Patellar dislocation
D) Tibial plateau fracture
E) Meniscal tear
Answer: C) Patellar dislocation
Explanation: Patellar dislocation typically occurs with a twisting injury, especially in athletes. The patella is usually displaced laterally, and patients often cannot extend the knee. This injury often resolves spontaneously, but recurrent dislocations are possible.
Pelvic Fracture
A 60-year-old male presents after falling from a height. He complains of severe pelvic pain and is unable to walk. X-ray shows multiple fractures in the pelvic ring.
Question: Which complication is the most immediate concern?
A) Sciatic nerve injury
B) Femoral nerve injury
C) Urethral injury
D) Bladder rupture
E) Avascular necrosis of the femoral head
Answer: C) Urethral injury
Explanation: In the setting of a pelvic fracture, especially involving the pelvic ring, the most immediate concern is urethral injury, particularly in males. The urethra is susceptible to injury due to the proximity of the bony structures. The inability to pass urine, blood at the meatus, or a high-riding prostate on the rectal exam are clinical clues.
Ischial Tuberosity Avulsion
A 17-year-old male sprinter reports a sudden onset of sharp pain in his buttocks while sprinting. He is unable to continue running and has tenderness over the ischial tuberosity.
Question: What structure is most likely injured?
A) Gluteus maximus tendon
B) Hamstring tendon
C) Adductor magnus tendon
D) Quadriceps tendon
E) Piriformis muscle
Answer: B) Hamstring tendon
Explanation: The hamstrings originate from the ischial tuberosity, and avulsion injuries can occur in athletes during activities requiring sudden acceleration, such as sprinting. Tenderness over the ischial tuberosity and difficulty with hip extension suggest a hamstring injury.
Iliotibial Band Syndrome
A 28-year-old marathon runner complains of pain on the lateral side of her knee, especially after long runs. The pain worsens with downhill running and is tender over the lateral femoral condyle.
Question: What is the most likely diagnosis?
A) Lateral collateral ligament strain
B) Patellofemoral pain syndrome
C) Iliotibial band syndrome
D) Popliteal tendonitis
E) Medial meniscus tear
Answer: C) Iliotibial band syndrome
Explanation: Iliotibial band syndrome is a common overuse injury in runners, characterized by pain at the lateral knee, particularly at the lateral femoral condyle. The pain worsens with activities like downhill running, and localized tenderness over the lateral knee is typica
