Neuromuscular Disorders — MCQs

10 questions

A 25 year old female presents with generalized restriction of eye movement in all direction, intermittent ptosis, proximal muscle weakness and fatigability.Which is the MOST useful test in making the diagnosis?

An infant previously diagnosed with a large muscular VSD comes to the office with complaints from the mother of fatigue and poor feeding over the past month. You note the child has not gained weight since the previous visit 2 months ago. The child is apathetic, tachypneic, and has wheezes and crackles on lung auscultation. What is the most likely cardiac diagnosis based on this patient's presentation?

Duchenne muscular dystrophy is inherited as:

A 4-year-old male child presents with muscle weakness. His mother reports that her child has difficulty in climbing stairs and getting up from the floor. On muscle biopsy, small degenerated muscle fibers and absence of dystrophin were found. What is the diagnosis?

Myasthenia gravis is a disorder of:

Which of the following findings is characteristic of Mallory-Weiss syndrome?

A 45-year-old female presents to the outpatient clinic with symptoms of pain, fatigue, and weakness in both lower limbs. She gives a history of paralysis affecting both lower limbs in childhood, from which she made a good functional recovery. Which of the following is the most likely suspected diagnosis?

Which of the following is not a known cause of neuroregression in children?

What is the significance of the persistence of the asymmetric tonic neck reflex in a 9-month-old infant?

Q10

Scissor gait is seen in which of the following conditions:

Neuromuscular Disorders Indian Medical PG Practice Questions and MCQs

Question 1: A 25 year old female presents with generalized restriction of eye movement in all direction, intermittent ptosis, proximal muscle weakness and fatigability.Which is the MOST useful test in making the diagnosis?

A. CPK
B. Edrophonium test (Correct Answer)
C. EMG
D. Muscle biopsy

Explanation: ***Edrophonium test*** - The **Edrophonium test** (Tensilon test) is highly useful for diagnosing **myasthenia gravis** due to its rapid onset and short duration of action. - In a patient with suspected myasthenia gravis, such as this one presenting with **generalized restriction of eye movement**, **intermittent ptosis**, and **fatigable proximal muscle weakness**, the administration of edrophonium will lead to a temporary but significant improvement in muscle strength. It works by inhibiting the breakdown of acetylcholine, thereby increasing its availability at the neuromuscular junction [1]. *CPK* - **Creatine phosphokinase (CPK)** levels are typically normal in myasthenia gravis, as it is a disorder of the **neuromuscular junction**, not a primary muscle disease. - Elevated CPK levels usually indicate muscle damage, seen in conditions like **myositis** or **muscular dystrophies**, which are not suggested by the patient's symptoms. *EMG* - **Electromyography (EMG)**, specifically **repetitive nerve stimulation (RNS)** or **single-fiber EMG (SFEMG)**, can show characteristic decremental responses or increased jitter/blocking in myasthenia gravis [2], but it is less direct and often more invasive than the Edrophonium test for initial diagnostic confirmation. - While supportive, it is generally considered a secondary diagnostic tool after a strong clinical suspicion and is not the *most useful* initial test compared to the rapid symptomatic improvement seen with edrophonium. *Muscle biopsy* - A **muscle biopsy** is generally not useful in diagnosing myasthenia gravis as the muscle tissue itself is structurally normal. - This diagnostic tool is reserved for primary **muscle disorders** like muscular dystrophies or inflammatory myopathies, which would show characteristic histological changes.

Question 2: An infant previously diagnosed with a large muscular VSD comes to the office with complaints from the mother of fatigue and poor feeding over the past month. You note the child has not gained weight since the previous visit 2 months ago. The child is apathetic, tachypneic, and has wheezes and crackles on lung auscultation. What is the most likely cardiac diagnosis based on this patient's presentation?

A. Congenital heart block
B. Prolonged QT syndrome
C. Congestive heart failure (Correct Answer)
D. Hypertrophic cardiomyopathy

Explanation: ***Congestive heart failure*** - The infant's symptoms of **fatigue**, **poor feeding**, **no weight gain**, **apathy**, **tachypnea**, and **wheezes/crackles** are classic signs of **congestive heart failure** in an infant. - A **large muscular VSD** can lead to significant left-to-right shunting, causing **pulmonary overcirculation** and symptoms of heart failure. *Congenital heart block* - This condition involves an abnormality in the heart's electrical conduction system, leading to a **slow heart rate (bradycardia)**. - While it can cause fatigue, it typically doesn't present with respiratory symptoms like **tachypnea** and **rales** unless profound bradycardia leads to heart failure. *Prolonged QT syndrome* - This is an **electrical disorder** that can cause **arrhythmias** and sudden cardiac death, often presenting with syncope or seizures. - It does not typically manifest with the signs of **pulmonary congestion** (wheezes, crackles) or feeding difficulties seen in this infant. *Hypertrophic cardiomyopathy* - This condition involves thickening of the heart muscle, leading to **outflow obstruction** and diastolic dysfunction. - While it can cause symptoms of poor feeding and fatigue, the prominent respiratory symptoms like **tachypnea** and **crackles** are more indicative of pulmonary venous congestion secondary to a large shunt.

Question 3: Duchenne muscular dystrophy is inherited as:

A. Autosomal dominant
B. Autosomal recessive
C. X-linked recessive (Correct Answer)
D. X-linked dominant
E. Mitochondrial inheritance

Explanation: ***X-linked recessive*** - Duchenne muscular dystrophy is primarily due to mutations in the **dystrophin gene**, located on the X chromosome, leading to X-linked recessive inheritance [1]. - Males are predominantly affected due to the presence of a single X chromosome, while females are carriers and may show mild symptoms [2]. *Autosomal dominant* - This mode of inheritance involves only one copy of a mutated gene for the condition to manifest, which is not the case for Duchenne muscular dystrophy. - Autosomal dominant disorders typically have a **vertical inheritance pattern**, unlike the skipped generations seen with X-linked recessive traits [2]. *X-linked dominant* - In X-linked dominant conditions, both males and females can be affected, which contrasts with the severe male predominance observed in Duchenne muscular dystrophy cases. - Female carriers of X-linked dominant disorders often experience more severe symptoms, which is not typical for this condition where females are usually asymptomatic carriers. *Autosomal recessive* - Autosomal recessive disorders require both copies of a gene to be mutated for the condition to be expressed, differing from the one-gene involvement in X-linked recessive disorders. - Conditions that follow this pattern often arise in families with a history of consanguinity, which is not the primary inheritance scenario for Duchenne muscular dystrophy. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Peripheral Nerves and Skeletal Muscles, pp. 1244-1245. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, p. 151.

Question 4: A 4-year-old male child presents with muscle weakness. His mother reports that her child has difficulty in climbing stairs and getting up from the floor. On muscle biopsy, small degenerated muscle fibers and absence of dystrophin were found. What is the diagnosis?

A. Myotonic dystrophy
B. Becker's muscle dystrophy
C. Limb-girdle muscular dystrophy
D. Duchenne muscular dystrophy (Correct Answer)

Explanation: ***Duchenne muscular dystrophy*** - The classic presentation of a young boy with **progressive muscle weakness**, difficulty climbing stairs (**Gowers' sign**), and **absent dystrophin** on muscle biopsy is characteristic of Duchenne muscular dystrophy. - It is an **X-linked recessive disorder** that leads to severe muscle degeneration and weakness due to a complete lack of functional dystrophin protein. *Myotonic dystrophy* - This condition is characterized by **myotonia** (delayed relaxation of muscles after contraction) and typically affects adults, although congenital forms exist. - While it causes muscle weakness, the primary differentiating feature of **myotonia** and its later onset are not present in this case. *Becker's muscle dystrophy* - Becker's muscular dystrophy (BMD) is also an X-linked recessive disorder and a milder form of muscular dystrophy, caused by a **reduced but still functional dystrophin** protein. - Patients with BMD typically present later in childhood or adolescence with slower progression and **some dystrophin** presence, unlike the absent dystrophin and early onset here. *Limb-girdle muscular dystrophy* - This is a group of muscular dystrophies that primarily affect the **pelvic and shoulder girdle muscles**. - It can present with similar weakness, but the **complete absence of dystrophin** found on biopsy points specifically to Duchenne muscular dystrophy, not typical limb-girdle dystrophy, which involves other genetic defects.

Question 5: Myasthenia gravis is a disorder of:

A. Spinal cord
B. Motor neuron
C. Neuromuscular junction (Correct Answer)
D. Peripheral nerve

Explanation: Neuromuscular junction - **Myasthenia gravis** is an **autoimmune disorder** where antibodies attack **acetylcholine receptors** at the **neuromuscular junction**, impairing nerve-to-muscle communication [1], [2]. - This leads to characteristic **muscle weakness** that worsens with activity and improves with rest [2]. *Spinal cord* - Disorders of the **spinal cord** typically involve sensory, motor, and autonomic deficits below the level of the lesion, often characterized by **spasticity** and **hyperreflexia**. - **Myasthenia gravis** does not directly affect the spinal cord, and its symptoms are distinct from spinal cord pathologies. *Motor neuron* - **Motor neuron diseases** (e.g., **ALS**) primarily affect the motor neurons in the brain and spinal cord, leading to progressive **muscle atrophy**, **fasciculations**, and **weakness** due to **denervation**. - Myasthenia gravis does not involve motor neuron degeneration; the neurons themselves are healthy. *Peripheral nerve* - **Peripheral nerve disorders** (e.g., **Guillain-Barré syndrome**) involve damage to nerves outside the brain and spinal cord, causing sensory changes (numbness, tingling), muscle weakness, and often **diminished reflexes**. - While myasthenia gravis causes weakness, it is due to a problem at the junction between the nerve and muscle, not within the nerve itself.

Question 6: Which of the following findings is characteristic of Mallory-Weiss syndrome?

A. Hematemesis (Correct Answer)
B. Melena
C. Epigastric pain
D. Vomiting

Explanation: ***Hematemesis*** - **Hematemesis** (vomiting blood) is the hallmark symptom of Mallory-Weiss syndrome, resulting from longitudinal tears in the distal esophagus or gastric cardia [1]. - These tears are typically caused by sudden increases in **intra-abdominal pressure**, often due to forceful retching or vomiting, leading to bleeding [1]. *Melena* - **Melena** indicates bleeding from the upper gastrointestinal (GI) tract, but it signifies digested blood, resulting in black, tarry stools, and is not the primary presentation of acute Mallory-Weiss tears. - While melena can occur if the bleeding from a Mallory-Weiss tear is slow or prolonged, **frank hematemesis** is the more immediate and characteristic sign. *Epigastric pain* - **Epigastric pain** can be present in Mallory-Weiss syndrome due to the forceful vomiting and the tears themselves, but it is a non-specific symptom found in many GI conditions. - It is not as specific or diagnostically crucial as hematemesis for identifying Mallory-Weiss tears. *Vomiting* - **Vomiting** or retching is often the precipitating event that causes Mallory-Weiss tears, but it is the cause, not the characteristic finding of the syndrome itself [1]. - The key diagnostic feature is the **subsequent bleeding** (hematemesis) that results from the tears, differentiating it from simple vomiting [1].

Question 7: A 45-year-old female presents to the outpatient clinic with symptoms of pain, fatigue, and weakness in both lower limbs. She gives a history of paralysis affecting both lower limbs in childhood, from which she made a good functional recovery. Which of the following is the most likely suspected diagnosis?

A. Post Polio syndrome (Correct Answer)
B. Polymyositis
C. Muscular Dystrophy
D. Neuropathy

Explanation: Polymyositis - Polymyositis is an **inflammatory myopathy** causing symmetrical proximal muscle weakness, often accompanied by elevated muscle enzymes like **creatine kinase**. [1] - It does not typically present with a history of childhood paralysis and subsequent late-onset symptoms related to that previous event. *Muscular Dystrophy* - Muscular dystrophies are a group of **genetic disorders** characterized by progressive muscle weakness and degeneration due to defective muscle proteins. - While they can cause weakness, their presentation and progression differ significantly from the episodic nature of polio and the late onset of new symptoms. *Neuropathy* - Neuropathy refers to damage or disease affecting the nerves, which can cause symptoms like weakness, numbness, and pain, typically with a more generalized or specific distribution. - While it causes weakness, neuropathy alone does not explain the history of childhood paralysis, recovery, and then specific late-onset symptoms tied to that past event.

Question 8: Which of the following is not a known cause of neuroregression in children?

A. Vitamin B12 deficiency
B. Ataxia telangiectasia
C. ADHD (Correct Answer)
D. Wilson's disease

Explanation: ***ADHD*** - **Attention-deficit/hyperactivity disorder (ADHD)** is a neurodevelopmental disorder characterized by persistent patterns of inattention, hyperactivity, and impulsivity. It is **not** a cause of neuroregression. - While ADHD can impact cognitive and behavioral functioning, it does not involve a loss of previously acquired developmental milestones or skills. *Wilson's disease* - **Wilson's disease** is an inherited disorder that causes **copper accumulation** in organs, particularly the liver and brain. - Neurological symptoms, including **neuroregression**, can occur due to copper toxicity in the central nervous system. *Vitamin B12 deficiency* - **Vitamin B12 deficiency** can lead to neurological complications such as **subacute combined degeneration** of the spinal cord and peripheral neuropathy. - In children, severe or prolonged deficiency can impair brain development and lead to **developmental regression**. *Ataxia telangiectasia* - **Ataxia telangiectasia** is a rare, neurodegenerative, inherited disease that affects multiple body systems. - It is characterized by progressive **cerebellar ataxia**, leading to **neuroregression** and intellectual disability over time.

Question 9: What is the significance of the persistence of the asymmetric tonic neck reflex in a 9-month-old infant?

A. Decreased muscle tone
B. Increased muscle tone (Correct Answer)
C. Normal phenomenon
D. None of the options

Explanation: ***Increased muscle tone*** - The **asymmetric tonic neck reflex (ATNR)** should integrate by **6 months of age**, and its persistence beyond this period is a sign of **neurological dysfunction**. - Persistent primitive reflexes, including ATNR, are often associated with **upper motor neuron lesions** and can manifest as increased muscle tone or **spasticity**. *Decreased muscle tone* - **Decreased muscle tone**, or **hypotonia**, is typically associated with **lower motor neuron lesions** or certain genetic conditions, not the persistence of primitive reflexes. - While some neurological conditions can cause hypotonia, persistent ATNR is a hallmark of problems leading to **hypertonia**. *Normal phenomenon* - The persistence of the ATNR beyond **6 months of age** is considered abnormal and indicates a potential developmental delay or neurological issue. - In a **9-month-old**, the reflex should have fully integrated, and its presence warrants further investigation. *None of the options* - As the persistence of the ATNR is indeed a significant finding, associated with increased muscle tone, this option is incorrect.

Question 10: Scissor gait is seen in which of the following conditions:

A. Polio
B. Cerebral palsy (Correct Answer)
C. Hyperbilirubinemia
D. Hyponatremia

Explanation: ***Cerebral palsy*** - **Scissor gait** is a characteristic presentation in individuals with **spastic cerebral palsy**, due to hyperactivity of adductor muscles, causing the legs to cross over each other. - This **spasticity** often results from damage to the brain's motor control centers during development. *Polio* - **Polio** primarily causes **flaccid paralysis** due to damage to anterior horn cells, leading to muscle weakness and atrophy, not spasticity. - The gait in polio is often characterized by muscle weakness, leading to a **waddling or steppage gait**, not scissoring. *Hyperbilirubinemia* - Severe **hyperbilirubinemia** in neonates can lead to **kernicterus**, causing **choreoathetosis**, dystonia, and hearing loss. - While it affects motor control, it typically results in involuntary movements and muscle rigidity (dystonia), but **scissor gait** is not a hallmark. *Hyponatremia* - **Hyponatremia** is an electrolyte imbalance that can cause neurological symptoms such as confusion, seizures, and coma. - It does not directly cause specific gait abnormalities like **scissor gait**; any gait disturbances would be secondary to altered mental status or seizures.

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