Peripheral nerve surgery basics US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Peripheral nerve surgery basics. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Peripheral nerve surgery basics US Medical PG Question 1: A patient presents with difficulty extending their wrist following trauma to the posterior forearm. Which of the following muscles would be most affected by injury to the posterior interosseous nerve?
- A. Extensor carpi ulnaris
- B. Extensor carpi radialis brevis
- C. Extensor pollicis longus
- D. Extensor digitorum (Correct Answer)
Peripheral nerve surgery basics Explanation: ***Extensor digitorum***
- The **posterior interosseous nerve (PIN)** innervates most muscles of the **posterior compartment of the forearm**, including the extensor digitorum. [1]
- Loss of function in the **extensor digitorum** would directly impair **extension of the fingers** and contribute significantly to difficulty extending the wrist. [1]
*Extensor carpi ulnaris*
- This muscle is also innervated by the **posterior interosseous nerve (PIN)** and contributes to **wrist extension** and **ulnar deviation**.
- While its innervation by the PIN is correct, injury to the PIN would affect this muscle, but the *extensor digitorum* is more broadly responsible for the stated primary symptom (difficulty extending the wrist), as its primary action is finger and thus wrist extension.
*Extensor carpi radialis brevis*
- While it is a **wrist extensor**, it is innervated by the **deep branch of the radial nerve** *before* it becomes the posterior interosseous nerve.
- Therefore, an isolated injury to the **posterior interosseous nerve** proper would typically spare the extensor carpi radialis brevis.
*Extensor pollicis longus*
- This muscle is indeed innervated by the **posterior interosseous nerve (PIN)** and acts to extend the **thumb**. [1]
- While it would be affected, the primary problem described is difficulty extending the *wrist*, for which the extensor digitorum plays a more significant and general role than the extensor pollicis longus.
Peripheral nerve surgery basics US Medical PG Question 2: A 74-year-old male is brought to the emergency department 1 hour after he fell from the top of the staircase at home. He reports pain in his neck as well as weakness of his upper extremities. He is alert and immobilized in a cervical collar. He has hypertension treated with hydrochlorothiazide. His pulse is 90/min and regular, respirations are 18/min, and blood pressure is 140/70 mmHg. Examination shows bruising and midline cervical tenderness. Neurologic examination shows diminished strength and sensation to pain and temperature in the upper extremities, particularly in the hands. Upper extremity deep tendon reflexes are absent. Strength, sensation, and reflexes in the lower extremities are intact. Anal sensation and tone are present. Babinski's sign is absent bilaterally. Which of the following is most likely to confirm the cause of this patient's neurologic examination findings?
- A. CT angiography of the neck
- B. MRI of the cervical spine without contrast (Correct Answer)
- C. X-ray of the cervical spine
- D. CT of the cervical spine with contrast
- E. Cervical myelography
Peripheral nerve surgery basics Explanation: ***MRI of the cervical spine without contrast***
- This patient presents with symptoms consistent with **central cord syndrome**, characterized by greater weakness in the upper extremities than the lower extremities, often following a hyperextension injury in older adults with pre-existing cervical spondylosis. **MRI is the gold standard for visualizing soft tissue injuries**, including spinal cord compression, edema, or hemorrhage, which are typical causes of central cord syndrome.
- Given the primary concern for spinal cord injury and the detailed neurological deficits indicating specific cord involvement, **MRI** offers the best resolution for evaluating the extent of cord damage, disc herniation, ligamentous injury, and pre-existing degenerative changes.
*CT angiography of the neck*
- **CT angiography** primarily evaluates the **vascular structures** of the neck (e.g., carotid and vertebral arteries) for dissection, stenosis, or occlusion.
- While vascular injury could occur in trauma, the patient's neurological findings (disproportionate upper extremity weakness, pain and temperature sensation loss) point more directly to **spinal cord pathology** rather than isolated vascular compromise as the primary cause.
*X-ray of the cervical spine*
- **X-rays** are useful for initial screening of **bony fractures** and significant dislocations but offer limited information about soft tissues, such as the spinal cord, ligaments, or intervertebral discs.
- They cannot adequately visualize the spinal cord damage responsible for the patient's specific neurological deficits, making it insufficient for confirming the cause of central cord syndrome.
*CT of the cervical spine with contrast*
- **CT scans** excel at visualizing **bony structures** and acute fractures, but even with contrast, they provide less detail of the **spinal cord parenchyma** and soft tissue ligaments compared to MRI.
- **Contrast** is typically used to highlight vascular structures, inflammatory processes, or tumors, which are not the primary diagnostic concerns suggested by this patient's acute post-traumatic presentation of central cord syndrome.
*Cervical myelography*
- **Myelography** involves injecting contrast into the subarachnoid space, followed by X-ray or CT imaging, to outline the spinal cord and nerve roots.
- While it can identify **spinal cord compression**, it is an **invasive procedure** with risks (e.g., headache, seizures) and has largely been replaced by the non-invasive and superior soft tissue imaging capabilities of MRI, especially in acute trauma.
Peripheral nerve surgery basics US Medical PG Question 3: A 62-year-old woman is brought to the physician because of 6 months of progressive weakness in her arms and legs. During this time, she has also had difficulty swallowing and holding her head up. Examination shows pooling of oral secretions. Muscle strength and tone are decreased in the upper extremities. Deep tendon reflexes are 1+ in the right upper and lower extremities, 3+ in the left upper extremity, and 4+ in the left lower extremity. Sensation to light touch, pinprick, and vibration are intact. Which of the following is the most likely diagnosis?
- A. Guillain-Barré syndrome
- B. Amyotrophic lateral sclerosis (Correct Answer)
- C. Spinal muscular atrophy
- D. Myasthenia gravis
- E. Syringomyelia
Peripheral nerve surgery basics Explanation: ***Amyotrophic lateral sclerosis***
- The patient presents with a combination of **upper motor neuron (UMN)** signs (hyperreflexia at 3+ and 4+, possibly stiffness contributing to difficulty holding head up) and **lower motor neuron (LMN)** signs (progressive weakness, decreased muscle tone, pooling of oral secretions due to bulbar involvement). This coexistence is pathognomonic for **ALS**.
- The **progressive nature** of the weakness in arms and legs, encompassing both UMN and LMN features without sensory deficits, is characteristic of ALS.
*Guillain-Barré syndrome*
- Typically presents with **acute or subacute onset (days to weeks)** of ascending weakness, often post-infectious, and characteristically causes **areflexia** or severely diminished deep tendon reflexes.
- This patient's symptoms have been progressive over **6 months**, and she exhibits significantly **increased reflexes** in some limbs, which is inconsistent with GBS.
*Spinal muscular atrophy*
- This is a group of **autosomal recessive disorders** that primarily affect **lower motor neurons**, leading to progressive muscle weakness and atrophy, usually presenting in infancy or childhood.
- The patient's age of presentation (62 years old) and the presence of **upper motor neuron signs** (hyperreflexia) rule out SMA.
*Myasthenia gravis*
- Presents with **fluctuating muscle weakness** that worsens with activity and improves with rest, often affecting ocular, bulbar, and limb muscles. It does not typically cause hyperreflexia or sustained upper motor neuron signs.
- While the patient has difficulty swallowing and pooling oral secretions, the **progressive, sustained weakness** and varied deep tendon reflexes (hypo to hyper) are not typical of myasthenia gravis without specific triggers like exertion.
*Syringomyelia*
- Characterized by a **syrinx (cyst) within the spinal cord**, leading to sensory deficits (often **"cape-like" loss of pain and temperature sensation**) and weakness/atrophy due to LMN damage, usually affecting the upper extremities.
- This patient's **intact sensation** and the presence of widespread UMN signs (hyperreflexia in lower limb) make syringomyelia an unlikely diagnosis.
Peripheral nerve surgery basics US Medical PG Question 4: A 29-year-old woman presents with progressive vision loss in her right eye and periorbital pain for 5 days. She says that she has also noticed weakness, numbness, and tingling in her left leg. Her vital signs are within normal limits. Neurological examination shows gait imbalance, positive Babinski reflexes, bilateral spasticity, and exaggerated deep tendon reflexes in the lower extremities bilaterally. FLAIR MRI is obtained and is shown in the image. Which of the following is the most likely cause of this patient’s condition?
- A. Amyotrophic lateral sclerosis
- B. Multiple sclerosis (Correct Answer)
- C. Acute disseminated encephalomyelitis
- D. Lead intoxication
- E. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL)
Peripheral nerve surgery basics Explanation: ***Multiple sclerosis***
- This patient's presentation with **optic neuritis** (vision loss, periorbital pain), disseminated neurological symptoms (**weakness, numbness, tingling in the left leg**, gait imbalance, spasticity, exaggerated DTRs, Babinski reflexes), and multifocal white matter lesions on MRI (FLAIR image would show **Dawson's fingers** or juxtacortical/infratentorial lesions) is highly characteristic of **multiple sclerosis**.
- The symptoms are **disseminated in space and time**, meaning different neurological deficits occurring at different locations in the CNS at different times, as suggested by the right eye and left leg involvement.
*Amyotrophic lateral sclerosis*
- Primarily a **motor neuron disease** affecting both upper and lower motor neurons, causing progressive muscle weakness, atrophy, and fasciculations.
- It does not typically involve **sensory deficits** (numbness, tingling), **optic neuritis**, or extensive white matter lesions on MRI.
*Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL)*
- A genetic (NOTCH3 gene) small vessel disease causing recurrent **strokes, migraine with aura**, and progressive cognitive decline, typically starting in middle age.
- While it causes white matter abnormalities on MRI, it does not typically present with **inflammatory demyelination** causing optic neuritis or the diverse neurological relapses seen in MS.
*Acute disseminated encephalomyelitis*
- This is a monophasic, immune-mediated demyelinating disorder that typically occurs **after an infection or vaccination**.
- It often has a more **acute and severe onset** with encephalopathy, and while it causes multifocal white matter lesions, it is typically a single event rather than relapsing-remitting course seen in MS.
*Lead intoxication*
- Lead poisoning can cause a variety of neurological symptoms, including **peripheral neuropathy** (motor and sensory), **encephalopathy**, and cognitive impairment.
- It does not typically cause **optic neuritis**, demyelinating lesions in the CNS, or the specific pattern of neurological deficits characteristic of MS.
Peripheral nerve surgery basics US Medical PG Question 5: A 34-year-old man is brought to the emergency department 3 hours after being bitten by a rattlesnake. He was hiking in the Arizona desert when he accidentally stepped on the snake and it bit his right leg. His pulse is 135/min and blood pressure is 104/81 mm Hg. Examination shows right lower leg swelling, ecchymosis, and blistering. Right ankle dorsiflexion elicits severe pain. A manometer inserted in the lateral compartment of the lower leg shows an intracompartmental pressure of 67 mm Hg. In addition to administration of the antivenom, the patient undergoes fasciotomy. Two weeks later, he reports difficulty in walking. Neurologic examination shows a loss of sensation over the lower part of the lateral side of the right leg and the dorsum of the right foot. Right foot eversion is 1/5. There is no weakness in dorsiflexion. Which of the following nerves is most likely injured in this patient?
- A. Sural nerve
- B. Tibial nerve
- C. Saphenous nerve
- D. Superficial peroneal nerve (Correct Answer)
- E. Deep peroneal nerve
Peripheral nerve surgery basics Explanation: ***Superficial peroneal nerve***
- The **superficial peroneal nerve** (also known as the superficial fibular nerve) is responsible for **foot eversion** (peroneus longus and brevis muscles) and provides sensory innervation to the **dorsum of the foot**, except for the web space between the first and second toes.
- The patient's inability to evert the foot and sensory loss on the dorsum of the foot, combined with a history of **compartment syndrome** and fasciotomy in the lateral compartment, strongly indicates injury to the superficial peroneal nerve.
*Sural nerve*
- The **sural nerve** provides sensory innervation to the **posterolateral aspect of the lower leg** and the lateral aspect of the foot.
- It does not innervate muscles involved in foot eversion or dorsiflexion, so its injury would not lead to the motor deficits described.
*Tibial nerve*
- The **tibial nerve** innervates the muscles of the posterior compartment of the leg, responsible for **plantarflexion** and inversion of the foot, and provides sensation to the sole of the foot.
- Its injury would lead to weakness in plantarflexion and sensory loss on the sole, not the symptoms described.
*Saphenous nerve*
- The **saphenous nerve** is a pure sensory nerve, supplying sensation to the **medial aspect of the lower leg and foot**.
- Its injury would result in sensory loss in this distribution but no motor deficits affecting foot eversion or dorsiflexion.
*Deep peroneal nerve*
- The **deep peroneal nerve** (also known as the deep fibular nerve) innervates the muscles of the anterior compartment of the leg, primarily responsible for **foot dorsiflexion** and toe extension, and provides sensation to the web space between the first and second toes.
- The patient has no weakness in dorsiflexion, ruling out significant injury to the deep peroneal nerve.
Peripheral nerve surgery basics US Medical PG Question 6: A 65-year-old man is referred by his primary care provider to a neurologist for leg pain. He reports a 6-month history of progressive bilateral lower extremity pain that is worse in his left leg. The pain is 5/10 in severity at its worst and is described as a "burning" pain. He has noticed that the pain is acutely worse when he walks downhill. He has started riding his stationary bike more often as it relieves his pain. His past medical history is notable for hypertension, diabetes mellitus, and a prior myocardial infarction. He also sustained a distal radius fracture the previous year after falling on his outstretched hand. He takes aspirin, atorvastatin, metformin, glyburide, enalapril, and metoprolol. He has a 30-pack-year smoking history and drinks 2-3 glasses of wine with dinner every night. His temperature is 99°F (37.2°C), blood pressure is 145/85 mmHg, pulse is 91/min, and respirations are 18/min. On exam, he is well-appearing and in no acute distress. A straight leg raise is negative. A valsalva maneuver does not worsen his pain. Which of the following is the most appropriate test to confirm this patient's diagnosis?
- A. Electromyography
- B. Ankle-brachial index
- C. Computerized tomography myelography
- D. Magnetic resonance imaging (Correct Answer)
- E. Radiography
Peripheral nerve surgery basics Explanation: **Magnetic resonance imaging**
- **Magnetic resonance imaging (MRI)** is the most appropriate test for diagnosing **lumbar spinal stenosis** because it provides detailed imaging of soft tissues, including the **spinal cord, nerve roots, and intervertebral discs**.
- The patient's symptoms of bilateral lower extremity pain, worse with downhill walking and relieved by stationary biking (which typically involves a flexed spine), are classic for **neurogenic claudication** caused by spinal stenosis.
*Electromyography*
- **Electromyography (EMG)** measures electrical activity of muscles and can identify **radiculopathy** or **neuropathy** but does not directly visualize the spinal canal or its contents to diagnose the cause of nerve compression.
- While it could show nerve root involvement, it wouldn't be the primary diagnostic test to confirm **spinal stenosis** itself.
*Ankle-brachial index*
- The **ankle-brachial index (ABI)** is used to diagnose **peripheral artery disease (PAD)**, which can also cause leg pain with activity (**vascular claudication**).
- However, the patient's pain being worse with downhill walking and relieved by spine flexion (like on a stationary bike) is more consistent with **neurogenic claudication** than vascular claudication.
*Computerized tomography myelography*
- **CT myelography** involves injecting contrast into the spinal canal and then performing a CT scan. While it can visualize the spinal canal, it is more invasive than MRI and exposes the patient to **ionizing radiation**.
- It is typically reserved for cases where MRI is contraindicated (e.g., pacemakers) or when MRI findings are inconclusive.
*Radiography*
- **Radiography (X-rays)** can show bony changes such as **spondylosis** and **degenerative disc disease**, which are often associated with spinal stenosis.
- However, X-rays do not directly visualize the **spinal cord, nerve roots, or soft tissue compression**, making them inadequate for confirming spinal stenosis as the cause of neurogenic claudication.
Peripheral nerve surgery basics US Medical PG Question 7: A 60-year-old woman is rushed to the emergency room after falling on her right elbow while walking down the stairs. She cannot raise her right arm. Her vital signs are stable, and the physical examination reveals loss of sensation over the upper lateral aspect of the right arm and shoulder. A radiologic evaluation shows a fracture of the surgical neck of the right humerus. Which of the following muscles is supplied by the nerve that is most likely damaged?
- A. Teres minor (Correct Answer)
- B. Teres major
- C. Subscapularis
- D. Infraspinatus
- E. Supraspinatus
Peripheral nerve surgery basics Explanation: ***Teres minor***
- A fracture of the **surgical neck of the humerus** often damages the **axillary nerve**, which innervates the **teres minor**.
- The axillary nerve also supplies the **deltoid muscle** and provides cutaneous sensation to the **upper lateral arm**, consistent with the patient's sensory loss.
*Teres major*
- This muscle is innervated by the **lower subscapular nerve**, which is less likely to be damaged in a surgical neck fracture.
- Its primary action is **adduction** and **internal rotation** of the arm.
*Subscapularis*
- The **subscapularis** is innervated by the **upper and lower subscapular nerves**.
- While it contributes to internal rotation, its nerve supply is typically protected in this type of fracture.
*Infraspinatus*
- The **infraspinatus** muscle is innervated by the **suprascapular nerve**.
- This nerve is generally not affected by a fracture of the surgical neck of the humerus.
*Supraspinatus*
- Similar to the infraspinatus, the **supraspinatus** is also innervated by the **suprascapular nerve**.
- Damage to this nerve due to a humeral surgical neck fracture is uncommon.
Peripheral nerve surgery basics US Medical PG Question 8: A 29-year-old woman presents to the primary care office for a recent history of falls. She has fallen 5 times over the last year. These falls are not associated with any preceding symptoms; she specifically denies dizziness, lightheadedness, or visual changes. However, she has started noticing that both of her legs feel weak. She's also noticed that her carpet feels strange beneath her bare feet. Her mother and grandmother have a history of similar problems. On physical exam, she has notable leg and foot muscular atrophy and 4/5 strength throughout her bilateral lower extremities. Sensation to light touch and pinprick is decreased up to the mid-calf. Ankle jerk reflex is absent bilaterally. Which of the following is the next best diagnostic test for this patient?
- A. MRI brain
- B. Ankle-brachial index
- C. Electromyography (including nerve conduction studies) (Correct Answer)
- D. Lumbar puncture
- E. Hemoglobin A1c
Peripheral nerve surgery basics Explanation: ***Electromyography (including nerve conduction studies)***
- The patient's symptoms of **progressive weakness**, **sensory deficits** (carpet feels strange, decreased sensation up to mid-calf), **muscular atrophy**, and **absent ankle reflexes**, along with a **family history**, are highly suggestive of a **hereditary peripheral neuropathy** (e.g., Charcot-Marie-Tooth disease).
- **Electromyography (EMG)** and **nerve conduction studies (NCS)** are essential for confirming peripheral neuropathy, differentiating between demyelinating and axonal involvement, and localizing the lesion.
*MRI brain*
- An MRI brain would be indicated for central nervous system pathology, but the patient's symptoms (distal weakness, sensory loss with a "stocking-glove" distribution, absent reflexes) are highly suggestive of a **peripheral neuropathy**.
- There is no indication of upper motor neuron signs or other CNS involvement to warrant a brain MRI at this stage.
*Ankle-brachial index*
- Ankle-brachial index (ABI) is used to diagnose **peripheral artery disease (PAD)**, which typically presents with claudication (pain with exertion) and ischemic changes.
- The patient's symptoms of sensory changes and progressive weakness are not characteristic of PAD.
*Lumbar puncture*
- A lumbar puncture is primarily used to analyze **cerebrospinal fluid (CSF)** for inflammatory, infectious, or neoplastic conditions affecting the CNS or nerve roots (e.g., Guillain-Barré syndrome, which has acute onset).
- Given the chronic and progressive nature of her symptoms and a positive family history, it is less likely to be an acute inflammatory process of the nerve roots.
*Hemoglobin A1c*
- Hemoglobin A1c is used to screen for or monitor **diabetes mellitus**, which can cause a **diabetic neuropathy**.
- While diabetes can cause peripheral neuropathy, the patient's young age, lack of typical diabetic risk factors, and strong family history point more strongly towards a hereditary condition. Glycemic control does not fully explain her presentation.
Peripheral nerve surgery basics US Medical PG Question 9: A 23-year-old college student was playing basketball when he fell directly onto his left elbow. He had sudden, intense pain and was unable to move his elbow. He was taken immediately to the emergency room by his teammates. He has no prior history of trauma or any chronic medical conditions. His blood pressure is 128/84 mm Hg, the heart rate is 92/min, and the respiratory rate is 14/min. He is in moderate distress and is holding onto his left elbow. On physical examination, pinprick sensation is absent in the left 5th digit and the medial aspect of the left 4th digit. Which of the following is the most likely etiology of this patient’s condition?
- A. Axillary neuropathy
- B. Median neuropathy
- C. Radial neuropathy
- D. Musculocutaneous neuropathy
- E. Ulnar neuropathy (Correct Answer)
Peripheral nerve surgery basics Explanation: ***Ulnar neuropathy***
- Direct trauma to the elbow, combined with **pinprick sensation loss** in the **5th digit** and the **medial aspect of the 4th digit**, is highly indicative of **ulnar nerve injury**.
- The ulnar nerve passes through the **cubital tunnel** at the elbow, making it vulnerable to compression or trauma from direct falls.
*Axillary neuropathy*
- An **axillary nerve injury** typically presents with weakness in **shoulder abduction** (deltoid muscle) and sensory loss over the **lateral aspect of the shoulder**.
- This clinical picture does not match the patient's sensory deficits in the fingers.
*Median neuropathy*
- **Median nerve injury** at the elbow would typically cause sensory loss in the **first three fingers and the lateral half of the fourth finger**, along with **weakness in thumb opposition** and **flexion of the index and middle fingers**.
- The sensory loss described in the patient does not align with median nerve distribution.
*Radial neuropathy*
- **Radial nerve injury** at the elbow level would primarily result in **wrist drop** and sensory loss over the **dorsal aspect of the hand**, particularly the **first three and a half digits**.
- These are not the clinical findings presented by the patient.
*Musculocutaneous neuropathy*
- **Musculocutaneous nerve injury** would cause weakness in **elbow flexion** (biceps and brachialis muscles) and sensory loss over the **lateral forearm**.
- The patient's reported sensory loss is in a different distribution and no specific motor deficits of elbow flexion are mentioned.
Peripheral nerve surgery basics US Medical PG Question 10: A 40-year-old woman presents with a ‘tingling’ feeling in the toes of both feet that started 5 days ago. She says that the feeling varies in intensity but has been there ever since she recovered from a stomach flu last week. Over the last 2 days, the tingling sensation has started to spread up her legs. She also reports feeling weak in the legs for the past 2 days. Her past medical history is unremarkable, and she currently takes no medications. Which of the following diagnostic tests would most likely be abnormal in this patient?
- A. Noncontrast CT of the head
- B. Serum hemoglobin concentration
- C. Nerve conduction studies (Correct Answer)
- D. Serum calcium concentration
- E. Transthoracic echocardiography
Peripheral nerve surgery basics Explanation: ***Nerve conduction studies***
- The patient's ascending **motor weakness** and **sensory paresthesias** following a gastrointestinal infection are classic symptoms of **Guillain-Barré Syndrome (GBS)**, which is characterized by **demyelination** of peripheral nerves.
- **Nerve conduction studies** would reveal **markedly slowed conduction velocities**, **conduction block**, and **prolonged distal latencies**, indicating the demyelinating neuropathy characteristic of GBS.
*Noncontrast CT of the head*
- This test is primarily used to evaluate **acute neurological deficits** suggestive of stroke, hemorrhage, or mass lesions within the brain.
- The patient's symptoms are consistent with a **peripheral neuropathy** and do not suggest a central nervous system pathology.
*Serum hemoglobin concentration*
- This measures the concentration of **hemoglobin in the blood** and is used to diagnose **anemia**.
- While anemia can cause fatigue, it does not typically cause the **ascending paralysis** and **paresthesias** described, nor is it directly related to a recent stomach flu in this manner.
*Serum calcium concentration*
- This measures the level of **calcium in the blood**, which is important for muscle and nerve function.
- While extreme imbalances can cause neurological symptoms, there is no direct indication or typical association between the patient's symptoms and a primary calcium disorder.
*Transthoracic echocardiography*
- This imaging test evaluates the **structure and function of the heart**.
- The patient's symptoms are neurological and do not suggest a primary cardiac etiology or complication that would warrant an echocardiogram.
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