Peripheral nerve disorders US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Peripheral nerve disorders. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Peripheral nerve disorders 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 disorders 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 disorders US Medical PG Question 2: A 33-year-old African American woman presents to the office complaining of blurry vision and headache for the past 2 weeks. She states that she has not been feeling herself lately and also fell down once after a dizzy episode. Her medical history is remarkable for hypertension and pulmonary sarcoidosis treated with hydralazine and prednisone respectively. She had a recent bout of acute optic neuritis, requiring high-dose IV methylprednisolone. Her temperature is 37°C (98.6°F), the blood pressure is 112/76 mm Hg, the pulse is 78/min, and the respirations are 14/min. On examination, the patient is mildly disoriented. Head and neck examination reveals a soft, supple neck and a right-sided facial droop. There is 5/5 muscle strength in all extremities. VDRL test is negative. A head MRI is pending. What is the most appropriate next step in the management of this patient?
- A. Methotrexate
- B. Plasmapheresis
- C. High-dose methylprednisolone (Correct Answer)
- D. Heparin
- E. Methotrexate and azathioprine
Peripheral nerve disorders Explanation: ***High-dose methylprednisolone***
- The patient's symptoms (blurry vision, headache, disorientation, facial droop, recent optic neuritis) are highly suggestive of a **central nervous system (CNS) demyelinating event**, possibly related to **neuroinflammation** in the setting of sarcoidosis or a new demyelinating disease.
- **High-dose intravenous corticosteroids** like methylprednisolone are the cornerstone treatment for acute exacerbations of demyelinating diseases (e.g., multiple sclerosis) and neuroinflammatory conditions like **neurosarcoidosis**, effectively reducing inflammation and neurological deficits.
*Methotrexate*
- **Methotrexate** is an immunosuppressant used as a **corticosteroid-sparing agent** in chronic inflammatory conditions, including sarcoidosis, but it is not the primary treatment for acute neurological exacerbations.
- Its onset of action is relatively slow, making it unsuitable for immediate management of acute neurological symptoms.
*Plasmapheresis*
- **Plasmapheresis** is typically considered for severe inflammatory demyelinating events that are **refractory to high-dose corticosteroids**, or in specific conditions like Guillain-Barré syndrome or myasthenia gravis crisis.
- It is not the initial treatment strategy when corticosteroids have not yet been adequately trialed for the current acute episode.
*Heparin*
- **Heparin** is an anticoagulant used to prevent or treat **thromboembolic events**, such as deep vein thrombosis, pulmonary embolism, or stroke due to clotting.
- There is no clinical evidence in the patient's presentation (e.g., focal neurological deficits without clear vascular territory involvement, normal blood pressure) to suggest an acute thrombotic event warranting heparin.
*Methotrexate and azathioprine*
- This combination represents a **dual immunosuppressive therapy** typically used for **chronic, severe, or refractory autoimmune and inflammatory conditions**, often as steroid-sparing agents or for long-term disease control.
- While relevant for chronic management of sarcoidosis, neither individually nor in combination are they appropriate for the **immediate treatment of acute neurological symptoms** which require rapid anti-inflammatory intervention.
Peripheral nerve disorders US Medical PG Question 3: A 35-year-old man is brought to the trauma bay by ambulance after sustaining a gunshot wound to the right arm. The patient is in excruciating pain and states that he can't move or feel his hand. The patient states that he has no other medical conditions. On exam, the patient's temperature is 98.4°F (36.9°C), blood pressure is 140/86 mmHg, pulse is 112/min, and respirations are 14/min. The patient is alert and his Glasgow coma scale is 15. On exam, he has a single wound on his right forearm without continued bleeding. The patient has preserved motor and sensation in his right elbow; however, he is unable to extend his wrist or extend his fingers further. He is able to clench his hand, but this is limited by pain. On sensory exam, the patient has no sensation to the first dorsal web space but has preserved sensation on most of the volar surface. Which of the following structures is most likely injured?
- A. Recurrent motor branch of the median nerve
- B. Main median nerve
- C. Lower trunk
- D. Ulnar nerve
- E. Radial nerve (Correct Answer)
Peripheral nerve disorders Explanation: ***Radial nerve***
- The inability to **extend the wrist and fingers** (wrist drop) is a classic sign of **radial nerve injury**, as it innervates the extensors of the forearm and hand.
- **Loss of sensation in the first dorsal web space** is also characteristic of radial nerve damage, as this area is supplied by the superficial radial nerve.
*Recurrent motor branch of the median nerve*
- This nerve primarily innervates the **thenar muscles** (flexor pollicis brevis, abductor pollicis brevis, opponens pollicis), affecting **thumb opposition**.
- Injury would primarily lead to **weakness in thumb movements**, not wrist or finger extension, and would spare sensation in the first dorsal web space.
*Main median nerve*
- The median nerve primarily innervates the **flexors of the forearm and hand**, and contributes to sensation on the **volar aspect of the thumb**, index, middle, and radial half of the ring finger.
- Injury would cause difficulty with **flexion of the wrist and fingers**, and loss of sensation on the volar surface, which is largely preserved in this patient.
*Lower trunk*
- The lower trunk of the brachial plexus (C8-T1) gives rise to the ulnar nerve and part of the median nerve, affecting **flexion of the wrist and fingers**, and intrinsic hand muscles.
- Injury would result in more widespread weakness affecting the **intrinsic hand muscles** and flexion, and would include sensory loss in the **ulnar nerve distribution**, which is not described.
*Ulnar nerve*
- The ulnar nerve primarily innervates the **intrinsic hand muscles** (excluding the thenar group) and the **flexor carpi ulnaris** and **medial half of flexor digitorum profundus**.
- Injury would typically cause **weakness in intrinsic hand functions** (e.g., finger abduction/adduction, ring and little finger flexion) and sensory loss on the **ulnar side of the hand**, not the dorsal web space.
Peripheral nerve disorders US Medical PG Question 4: A 52-year-old female with a history of poorly-controlled diabetes presents to her primary care physician because of pain and tingling in her hands. These symptoms began several months ago and have been getting worse such that they interfere with her work as a secretary. She says that the pain is worse in the morning and she has been woken up at night by the pain. The tingling sensations have been located primarily in the thumb, index and middle fingers. On physical exam atrophy of the thenar eminence is observed and the pain is reproduced when the wrist is maximally flexed. The most likely cause of this patient's symptoms affects which of the nerves shown in the image provided?
- A. D (Correct Answer)
- B. A
- C. B
- D. C
- E. E
Peripheral nerve disorders Explanation: ***D***
- The patient's symptoms of pain and tingling in the **thumb, index, and middle fingers**, worse in the morning and at night, along with thenar atrophy and positive Phalen's sign (pain with maximal wrist flexion), are classic for **carpal tunnel syndrome**.
- **Carpal tunnel syndrome** is caused by compression of the **median nerve** (represented by D in the provided image).
*A*
- This nerve represents the **radial nerve**, which primarily innervates the extensors of the wrist and fingers and provides sensation to the posterior aspect of the forearm and hand.
- Compression or damage to the radial nerve typically causes "wrist drop" and sensory loss in a different distribution, not consistent with the patient's symptoms.
*B*
- This nerve represents the **ulnar nerve**, which innervates muscles of the hand (excluding those of the thenar eminence) and provides sensation to the little finger and half of the ring finger.
- Ulnar nerve compression (e.g., at the elbow in **cubital tunnel syndrome**) would lead to symptoms in the "pinky" and ring finger, and atrophy of the hypothenar eminence, which are not seen here.
*C*
- This nerve represents the **axillary nerve**, which innervates the deltoid and teres minor muscles and provides sensation over the lateral shoulder.
- Damage to the axillary nerve would result in shoulder weakness and sensory loss over the deltoid, far from the patient's hand symptoms.
*E*
- This nerve represents the **musculocutaneous nerve**, which innervates the biceps and brachialis muscles and provides sensation to the lateral forearm.
- Injury to this nerve would cause weakness in elbow flexion and sensory loss in the forearm, not hand pain and tingling in the specified distribution.
Peripheral nerve disorders US Medical PG Question 5: A research team is studying certain congenital anomalies of the respiratory tract. The method consists of marking a certain germinal layer with an isotope, following its development stages in chicken embryos, and finally analyzing the specimen. A given specimen of tissue is presented in the exhibit. Which of the following germinal structures most likely gave rise to the epithelial lining of this specimen?
- A. Ectoderm
- B. Neural crest
- C. Mesoderm
- D. Endoderm (Correct Answer)
- E. Surface ectoderm
Peripheral nerve disorders Explanation: ***Endoderm***
- The **epithelial lining** of the entire respiratory tract, including the larynx, trachea, bronchi, and lungs, is derived from the **endoderm**.
- The **laryngotracheal groove** develops from the ventral wall of the primitive foregut, which is endodermal in origin, further differentiating into the respiratory tree.
*Ectoderm*
- The **ectoderm** primarily forms the epidermis, hair, nails, and the nervous system (brain and spinal cord).
- It does not contribute to the internal epithelial lining of the respiratory tract.
*Neural crest*
- **Neural crest cells** contribute to a wide variety of structures, including components of the peripheral nervous system, head mesenchyme, and melanocytes.
- They are not involved in forming the epithelial lining of the respiratory system.
*Mesoderm*
- The **mesoderm** forms the connective tissue, cartilage, and muscle components of the respiratory tract, such as the smooth muscle and cartilage rings of the trachea and bronchi, and the visceral pleura.
- However, it does not form the epithelial lining itself.
*Surface ectoderm*
- **Surface ectoderm** specifically gives rise to the epidermis, hair, nails, and glands of the skin, as well as the oral cavity epithelium.
- It does not contribute to the internal epithelial structures of the respiratory tract.
Peripheral nerve disorders US Medical PG Question 6: A 55-year-old man presents with burning and shooting in his feet and lower legs, which becomes more severe at night. In the past 6 months, the pain has become much worse and disturbs his sleep. He has a history of type 2 diabetes mellitus and essential hypertension. Which of the following best represent the etiology of this patient’s condition?
- A. Autonomic neuropathy
- B. Distal symmetric sensorimotor polyneuropathy (Correct Answer)
- C. Isolated peripheral nerve neuropathy
- D. Isolated cranial nerve neuropathy
- E. Radiculopathy
Peripheral nerve disorders Explanation: ***Distal symmetric sensorimotor polyneuropathy***
- This condition is the most common form of **diabetic neuropathy**, characterized by **burning, shooting pain** predominantly in the feet and lower legs, **worsening at night**.
- The patient's history of **type 2 diabetes mellitus** is a strong risk factor, and the symmetric distribution of symptoms indicates a polyneuropathy, affecting both sensory and motor nerves distally.
*Autonomic neuropathy*
- This involves damage to the **autonomic nervous system**, leading to symptoms like **orthostatic hypotension**, gastroparesis, or bladder dysfunction.
- While common in diabetes, it does not typically present with the described **burning and shooting pain** in the extremities.
*Isolated peripheral nerve neuropathy*
- This diagnosis implies damage to a **single peripheral nerve**, often due to compression or trauma, resulting in focal symptoms.
- The patient's symptoms are **bilateral and symmetric**, affecting multiple nerves, rather than an isolated nerve.
*Isolated cranial nerve neuropathy*
- This involves damage to one or more of the **cranial nerves**, leading to symptoms such as vision changes, facial weakness, or difficulty swallowing.
- The described symptoms of **pain in the feet and lower legs** do not align with cranial nerve involvement.
*Radiculopathy*
- **Radiculopathy** refers to nerve root compression, often causing pain, numbness, or weakness in a **dermatomal or myotomal distribution**.
- The patient's diffuse, symmetric symptoms in the feet and lower legs are more consistent with a polyneuropathy than a specific nerve root compression.
Peripheral nerve disorders US Medical PG Question 7: A 27-year-old woman comes to the emergency department because of progressive numbness and weakness in her left arm and left leg for 2 days. During this period, she has also had urinary urgency and incontinence. Three months ago, she had blurry vision, difficulty distinguishing colors, and headache for one week, all of which have resolved. The patient has smoked a half pack of cigarettes daily for 10 years and drinks four glasses of wine each week. Her temperature is 37°C (98.6°F), pulse is 78/min, respirations are 14/min, and blood pressure is 110/68 mm Hg. Examination shows 3/5 strength in the left arm and leg, and 5/5 strength on the right side. Upon flexion of the neck, the patient experiences a shooting electric sensation that travels down the spine. MRI of the brain shows gadolinium-enhancing lesions in the right central sulcus, cervical spinal cord, and optic nerve. Which of the following is the most appropriate next step in the management of this patient?
- A. Administer lorazepam
- B. Plasmapheresis
- C. Administer IV methylprednisolone (Correct Answer)
- D. Glatiramer acetate therapy
- E. Administer tissue plasminogen activator
Peripheral nerve disorders Explanation: ***Administer IV methylprednisolone***
- This patient presents with an acute exacerbation of **multiple sclerosis (MS)**, characterized by new neurological deficits (numbness, weakness, urinary urgency) and resolving symptoms that point to prior demyelination (blurry vision).
- High-dose **intravenous corticosteroids** like methylprednisolone are the first-line treatment for acute MS relapses to reduce inflammation and shorten the duration of the attack.
*Administer lorazepam*
- **Lorazepam** is a benzodiazepine primarily used for anxiety, seizures, or agitation and does not address the underlying inflammatory process of an acute MS exacerbation.
- While some MS patients may experience anxiety, it is not the indicated treatment for acute neurological deficits.
*Plasmapheresis*
- **Plasmapheresis** is considered for severe MS exacerbations that are refractory to high-dose corticosteroids.
- It is not typically the first-line treatment in an acute relapse unless corticosteroids have failed.
*Glatiramer acetate therapy*
- **Glatiramer acetate** is a disease-modifying therapy (DMT) for MS, used to reduce the frequency of relapses and prevent disease progression.
- It is administered long-term but is not an appropriate treatment for an acute MS exacerbation.
*Administer tissue plasminogen activator*
- **Tissue plasminogen activator (tPA)** is a thrombolytic agent used to treat acute ischemic stroke by dissolving blood clots.
- This patient's symptoms are neurological but are consistent with demyelination rather than an ischemic event, making tPA inappropriate.
Peripheral nerve disorders US Medical PG Question 8: A 35-year-old man presents to the primary care office with a recent history of frequent falls. He had been able to walk normally until about a year ago when he started noticing that both of his legs felt weak. He's also had some trouble with feeling in his feet. These 2 problems have caused multiple falls over the last year. On physical exam, he has notable leg and foot muscular atrophy and 4/5 strength throughout his bilateral lower extremities. Sensation to light touch and pinprick is absent up to the mid-calf. Ankle jerk reflex is absent bilaterally. A photo of the patient's foot is shown. Which of the following best describes the etiology of this patient's condition?
- A. Metabolic
- B. Genetic (Correct Answer)
- C. Ischemic
- D. Autoimmune
- E. Infectious
Peripheral nerve disorders Explanation: ***Genetic***
- The combination of **progressive weakness and sensory deficits** starting in the distal extremities, **muscle atrophy**, absent ankle jerks, and the characteristic foot deformity (*pes cavus* and hammertoes, visible in the image) in a 35-year-old strongly suggests a hereditary neuropathy, most commonly **Charcot-Marie-Tooth disease (CMT)**.
- CMT is a group of inherited neurological disorders characterized by slowly progressive degeneration of peripheral nerves, leading to distal muscle weakness and sensory loss, and is the most prevalent inherited peripheral neuropathy.
*Metabolic*
- While metabolic conditions can cause neuropathy (e.g., **diabetes**), they typically present with a more classic "stocking-glove" distribution of sensory loss, and the characteristic foot deformities and progressive severe atrophy seen here are less typical as initial presentation without a clear history of underlying metabolic disease.
- Absence of other metabolic derangements, such as diabetes, thyroid dysfunction, or vitamin deficiencies, makes this less likely to be the primary cause.
*Ischemic*
- **Ischemic neuropathies** are usually acute, painful, and often associated with vascular risk factors or specific arterial occlusions, which are not described in this patient's chronic, bilateral, and symmetric presentation.
- There is no mention of claudication or other signs of vascular insufficiency.
*Autoimmune*
- **Autoimmune neuropathies** like **Guillain-Barré Syndrome (GBS)** or **Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP)** often have a more acute or subacute onset (GBS) or relapsing-remitting course (CIDP), and GBS typically presents with ascending weakness reaching a nadir and then improving, which is not consistent with this patient's chronic, progressive course.
- While CIDP can be chronic, the classic inherited foot deformities are not typically seen, and the pattern of nerve involvement might differ.
*Infectious*
- **Infectious neuropathies** (e.g., HIV, Lyme disease, leprosy) would typically have associated systemic symptoms, a different progression pattern, or specific exposures that are not mentioned in the patient's history.
- The chronic, slowly progressive nature with specific deformities makes a common infectious cause less likely compared to a genetic disorder.
Peripheral nerve disorders US Medical PG Question 9: A 54-year-old man is brought to the emergency department because of progressive tingling and weakness in both of his legs for the past two days. The patient reports that his symptoms interfere with his ability to walk. Two weeks ago, he had an upper respiratory tract infection, which resolved spontaneously. His vital signs are within normal limits. Examination shows weakness in the lower extremities with absent deep tendon reflexes. Reflexes are 1+ in the upper extremities. Sensation to pinprick and light touch is intact. Romberg's test is negative. Laboratory studies show a leukocyte count of 12,000/mm3. Cerebrospinal fluid analysis results show:
Opening pressure normal
Protein 200 mg/dL
Glucose 70 mg/dL
White blood cells 4/mm3
This patient is at increased risk for which of the following conditions?
- A. Respiratory failure (Correct Answer)
- B. Dementia
- C. Hypertrophic cardiomyopathy
- D. Thymoma
- E. Urinary incontinence
Peripheral nerve disorders Explanation: ***Respiratory failure***
- The patient's presentation is consistent with **Guillain-Barré Syndrome (GBS)**, characterized by **ascending paralysis**, areflexia, and a history of preceding infection.
- As the paralysis ascends, it can affect the **respiratory muscles** (diaphragm and intercostal muscles), leading to life-threatening respiratory failure requiring mechanical ventilation.
*Dementia*
- **Dementia** is a chronic neurodegenerative condition characterized by progressive cognitive decline, memory impairment, and functional deficits.
- It does not present with acute, rapidly progressing **motor weakness** and **areflexia** as seen in this patient.
*Hypertrophic cardiomyopathy*
- **Hypertrophic cardiomyopathy** is a genetic heart condition causing thickening of the heart muscle, leading to impaired diastolic filling and potential arrhythmias.
- It does not explain the patient's neurological symptoms of **progressive weakness**, **areflexia**, or the characteristic CSF findings.
*Thymoma*
- A **thymoma** is a tumor of the thymus gland, most commonly associated with **myasthenia gravis**, an autoimmune disorder causing fluctuating muscle weakness that worsens with activity.
- The patient's symptoms of progressive, ascending paralysis with absent reflexes are **inconsistent with myasthenia gravis**.
*Urinary incontinence*
- While urinary symptoms can be seen in some neurological conditions, **urinary incontinence** is not a primary or hallmark feature of **Guillain-Barré Syndrome** in its acute phase unless severe autonomic dysfunction or profound flaccid paralysis affecting the bladder occurs.
- The most immediate and life-threatening complication in GBS is respiratory compromise due to ascending paralysis.
Peripheral nerve disorders US Medical PG Question 10: A 67-year-old man presents with pain in both legs. He says the pain is intermittent in nature and has been present for approximately 6 months. The pain increases with walking, especially downhill, and prolonged standing. It is relieved by lying down and leaning forward. Past medical history is significant for type 2 diabetes mellitus, hypercholesterolemia, and osteoarthritis. The patient reports a 56-pack-year history but denies any alcohol or recreational drug use. His vital signs include: blood pressure 142/88 mm Hg, pulse 88/min, respiratory rate 14/min, temperature 37°C (98.6°F). On physical examination, the patient is alert and oriented. Muscle strength is 5/5 in his upper and lower extremities bilaterally. Babinski and Romberg tests are negative. Pulses measure 2+ in upper and lower extremities bilaterally. Which of the following is the next best step in the management of this patient?
- A. MRI of the spine (Correct Answer)
- B. CT angiography of the lower extremities
- C. Ankle-brachial index
- D. Cilostazol
- E. Epidural corticosteroid injection
Peripheral nerve disorders Explanation: ***MRI of the spine***
- The patient's symptoms of **intermittent leg pain worsened by walking (especially downhill) and prolonged standing**, and **relieved by lying down and leaning forward**, are highly classic for **neurogenic claudication** due to **lumbar spinal stenosis**.
- An **MRI of the spine** is the *gold standard* for diagnosing spinal stenosis, clearly visualizing nerve root compression and the degree of canal narrowing.
*CT angiography of the lower extremities*
- This imaging is used to assess **peripheral artery disease** (PAD) but the patient's symptoms are inconsistent with vascular claudication.
- **Vascular claudication** typically improves with rest, not with specific postures like leaning forward.
*Ankle-brachial index*
- The **ankle-brachial index (ABI)** is a non-invasive test to screen for **peripheral artery disease (PAD)**.
- While the patient has risk factors for PAD (diabetes, hypercholesterolemia, smoking), his symptoms are classic for neurogenic claudication, and his **2+ pulses** in the lower extremities make PAD less likely.
*Cilostazol*
- **Cilostazol** is a phosphodiesterase inhibitor used to treat symptoms of **intermittent claudication** caused by **peripheral artery disease (PAD)**.
- Since the patient's symptoms are more consistent with neurogenic claudication rather than vascular claudication, cilostazol would not be the appropriate initial step.
*Epidural corticosteroid injection*
- An **epidural corticosteroid injection** is a treatment option for symptomatic spinal stenosis but is not the *initial diagnostic step*.
- Diagnosis with an **MRI** is necessary before considering targeted therapeutic interventions like injections.
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