Peripheral nerve disorders — MCQs

10 questions

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 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 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 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 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 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 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 7-year-old boy is brought to the emergency department by his parents. He is complaining of left-sided knee pain which has progressively increased in severity over the past 2 days. It started when he was playing football with his brothers but he does not recall falling or getting any injury. Past medical history is significant for prolonged bleeding and easy bruising. His maternal uncle has similar problems. Physical exam reveals swollen and painful left knee. His laboratory investigations reveal: Hemoglobin 11.8 g/dL WBC count 7,000/mL Platelets 250,000/mL INR 0.9 aPTT 62 sec, fully corrected with a mixing study Which of the following disorders have the same mode of inheritance as this patient’s disease?

A 44-year-old woman presents to her primary care physician’s office with episodes of pain in her right hand. She says that the pain is most significant at night and awakens her from sleep numerous times. When she experiences this pain, she immediately puts her hand under warm running water or shakes her hand. She has also experienced episodes of numbness in the affected hand. Driving and extending the right arm also provoke her symptoms. She denies any trauma to the hand or associated weakness. Medical history is notable for hypothyroidism treated with levothyroxine. She works as a secretary for a law firm. On physical exam, when the patient hyperflexes her wrist, pain and paresthesia affect the first 3 digits of the right hand. Which of the following is the confirmatory diagnostic test for this patient?

Q10

A 66-year-old woman comes to the physician because of a 1-week history of pruritic blister formation. Physical examination shows multiple 1–3 cm bullae on the palms, soles, lower legs, and inguinal folds. Gentle rubbing of the skin does not result in sloughing of the epidermis. Immunofluorescence studies of a perilesional skin biopsy specimen are most likely to show deposition of antibodies in which of the following areas?

Peripheral nerve disorders US Medical PG Practice Questions and MCQs

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)

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.

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

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.

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)

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.

Question 4: 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

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.

Question 5: 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

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.

Question 6: 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

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.

Question 7: 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

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.

Question 8: A 7-year-old boy is brought to the emergency department by his parents. He is complaining of left-sided knee pain which has progressively increased in severity over the past 2 days. It started when he was playing football with his brothers but he does not recall falling or getting any injury. Past medical history is significant for prolonged bleeding and easy bruising. His maternal uncle has similar problems. Physical exam reveals swollen and painful left knee. His laboratory investigations reveal: Hemoglobin 11.8 g/dL WBC count 7,000/mL Platelets 250,000/mL INR 0.9 aPTT 62 sec, fully corrected with a mixing study Which of the following disorders have the same mode of inheritance as this patient’s disease?

A. Hereditary spherocytosis
B. Alkaptonuria
C. Duchenne muscular dystrophy (Correct Answer)
D. Sickle cell disease
E. Huntington's disease

Explanation: ***Duchenne muscular dystrophy*** - The patient's presentation with **hemarthrosis** (knee pain and swelling without trauma), **prolonged bleeding**, and **easy bruising**, along with a **prolonged aPTT** that corrects with a mixing study, is highly suggestive of **hemophilia A or B**. Both conditions are **X-linked recessive disorders**, affecting males predominantly. - **Duchenne muscular dystrophy** is also an **X-linked recessive disorder**, making its mode of inheritance identical to the suspected diagnosis of hemophilia in this patient. *Hereditary spherocytosis* - This condition is inherited in an **autosomal dominant** pattern, which is different from the mode of inheritance for hemophilia. - It is characterized by **hemolytic anemia** due to a defect in red blood cell membrane proteins. *Alkaptonuria* - Alkaptonuria is an **autosomal recessive** disorder, caused by a deficiency of homogentisate 1,2-dioxygenase. - It leads to the accumulation of **homogentisic acid**, causing **dark urine** when exposed to air, **ochronosis**, and **arthropathy**, distinct from the patient's bleeding disorder. *Sickle cell disease* - **Sickle cell disease** is an **autosomal recessive** disorder, characterized by abnormal hemoglobin leading to chronic hemolytic anemia and vaso-occlusive crises. - While it can cause joint pain due to avascular necrosis or infarction, its inheritance pattern is different from the patient's condition. *Huntington's disease* - **Huntington's disease** is an **autosomal dominant** neurodegenerative disorder that manifests with progressive motor, cognitive, and psychiatric symptoms, typically in middle age. - Its inheritance pattern and clinical presentation are distinct from the patient's bleeding disorder.

Question 9: A 44-year-old woman presents to her primary care physician’s office with episodes of pain in her right hand. She says that the pain is most significant at night and awakens her from sleep numerous times. When she experiences this pain, she immediately puts her hand under warm running water or shakes her hand. She has also experienced episodes of numbness in the affected hand. Driving and extending the right arm also provoke her symptoms. She denies any trauma to the hand or associated weakness. Medical history is notable for hypothyroidism treated with levothyroxine. She works as a secretary for a law firm. On physical exam, when the patient hyperflexes her wrist, pain and paresthesia affect the first 3 digits of the right hand. Which of the following is the confirmatory diagnostic test for this patient?

A. Magnetic resonance imaging
B. Needle electromyography
C. Nerve conduction studies (Correct Answer)
D. Nerve biopsy
E. Tinel test

Explanation: ***Nerve conduction studies*** - **Nerve conduction studies (NCS)** are the most sensitive and specific diagnostic test for **carpal tunnel syndrome**, definitively confirming median nerve compression. - They measure the speed and amplitude of electrical signals through the **median nerve** at the wrist, identifying slowed conduction across the carpal tunnel. *Magnetic resonance imaging* - While MRI can visualize soft tissues and nerve pathology, it is not typically the **first-line confirmatory test** for carpal tunnel syndrome due to its lower sensitivity compared to NCS. - MRI is more useful for identifying **structural abnormalities** like tumors or synovitis, which might cause secondary nerve compression. *Needle electromyography* - **Electromyography (EMG)** involves inserting a needle into muscles to assess their electrical activity; it helps evaluate for **axonopathy** and muscle denervation. - While EMG is often performed alongside NCS, it primarily assesses muscle function and nerve damage severity, rather than directly confirming nerve compression itself, which is best done by NCS. *Nerve biopsy* - **Nerve biopsy** is an invasive procedure generally reserved for diagnosing demyelinating or infiltrative neuropathies when less invasive tests are inconclusive. - It carries risks and is **unnecessary** and inappropriate for diagnosing a common compressive neuropathy like carpal tunnel syndrome. *Tinel test* - The **Tinel test** is a clinical provocative maneuver where percussion over the median nerve at the wrist elicits tingling or pain. - It is a **screening tool** and part of the physical exam for carpal tunnel syndrome, but it is not a confirmatory diagnostic test due to its variable sensitivity and specificity.

Question 10: A 66-year-old woman comes to the physician because of a 1-week history of pruritic blister formation. Physical examination shows multiple 1–3 cm bullae on the palms, soles, lower legs, and inguinal folds. Gentle rubbing of the skin does not result in sloughing of the epidermis. Immunofluorescence studies of a perilesional skin biopsy specimen are most likely to show deposition of antibodies in which of the following areas?

A. In dermal papillae
B. Between epidermal keratinocytes
C. No staining
D. In dermal vessel walls
E. At the dermoepidermal junction (Correct Answer)

Explanation: ***At the dermoepidermal junction*** - This presentation of **tense bullae** on flexural surfaces in an elderly patient, with a negative **Nikolsky's sign** (no epidermal sloughing with rubbing), is classic for **bullous pemphigoid**. - **Direct immunofluorescence** in bullous pemphigoid typically reveals linear deposits of **IgG** and/or **C3** at the **dermoepidermal junction (basement membrane zone)**. *In dermal papillae* - Deposition in dermal papillae is characteristic of **dermatitis herpetiformis**, which typically presents with intensely pruritic papules and vesicles, often on extensor surfaces. - The morphology and distribution of lesions in this patient (large bullae on palms, soles, inguinal folds) are not consistent with dermatitis herpetiformis. *Between epidermal keratinocytes* - Deposition of autoantibodies (IgG) between epidermal keratinocytes is a hallmark of **pemphigus vulgaris**, resulting in suprabasal blistering and a positive **Nikolsky's sign**. - This patient exhibits **tense bullae** and a **negative Nikolsky's sign**, which rules out pemphigus vulgaris. *No staining* - The presence of pruritic blister formation in an elderly patient strongly suggests an autoimmune bullous disease, for which direct immunofluorescence is a key diagnostic tool. - A lack of staining would indicate a non-immunological cause of blistering or a different type of dermatological condition, which is unlikely given the clinical picture. *In dermal vessel walls* - Immune complex deposition in dermal vessel walls is characteristic of diseases like **leukocytoclastic vasculitis**, which presents with palpable purpura rather than tense bullae. - The clinical presentation of pruritic bullae in this patient is inconsistent with a vasculitis.

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