FINALS: DISORDER OF THE NEUROMUSCULAR JUNCTION

Question 1

What is the hallmark pathology of Myasthenia Gravis (MG)?

Answer 1

Damage to the endplates due to complement-mediated lysis, loss of acetylcholine receptors, and accelerated receptor degradation.

Question 2

What is the most common etiology associated with Myasthenia Gravis?

Answer 2

Thymus gland abnormalities, including thymoma, leading to excessive synthesis of thymic hormones and immune alterations.

Question 3

What are the hallmark symptoms of Myasthenia Gravis?

Answer 3

Fluctuating weakness, ptosis, diplopia, dysarthria, dysphagia, and limb and neck muscle weakness.

Question 4

What is the key diagnostic test for Myasthenia Gravis?

Answer 4

Electrophysiologic evidence of abnormal neuromuscular transmission and detection of circulating antibodies to acetylcholine receptors.

Question 5

How is Myasthenia Gravis treated?

Answer 5

Anticholinesterase drugs (e.g., Pyridostigmine), thymectomy, plasmapheresis, prednisone, IVIG, and immunosuppressive agents like azathioprine.

Question 6

What distinguishes Lambert-Eaton Myasthenic Syndrome (LEMS) from Myasthenia Gravis?

Answer 6

LEMS involves antibodies against voltage-gated calcium channels, autonomic symptoms (e.g., dry mouth, constipation), and absence of the “4 Ds” (dysphagia, dysarthria, diplopia, dyspnea).

Question 7

What is the hallmark symptom of Lambert-Eaton Syndrome on EMG testing?

Answer 7

Incremental response in the amplitude of muscle action potentials with high-frequency stimulation.

Question 8

What are the primary causes of botulism?

Answer 8

Toxins produced by Clostridium botulinum, commonly found in soil, foodborne sources, anaerobic wounds, and inhalation.

Question 9

What are the major symptoms of botulism?

Answer 9

Dry sore throat, blurred vision, diplopia, hypohidrosis, symmetric descending paralysis, and respiratory failure.

Question 10

How is botulism managed?

Answer 10

Respiratory support, administration of antitoxins, and use of drugs like guanidine hydrochloride for symptomatic relief.

Question 11

What are the key signs of Myasthenia Gravis (MG) affecting the eyes?

Answer 11

Weakness of the levator palpebrae (causing ptosis) and paralysis of ocular muscles, leading to diplopia and ophthalmoplegia.

Question 12

What are the common findings in laboratory data for Myasthenia Gravis?

Answer 12

Presence of antibodies to acetylcholine receptors, normal CSF, decremental response on repetitive nerve stimulation (RNS), and abnormalities on intercostal muscle biopsy.

Question 13

: What is a Myasthenic Crisis?

Answer 13

A life-threatening condition requiring assisted ventilation due to severe dysarthria, dysphagia, and respiratory muscle weakness.

Question 14

What tests are used for diagnosing Myasthenia Gravis?

Answer 14

Neostigmine test, edrophonium chloride test, and electrophysiological studies such as EMG.

Question 15

What are differential diagnoses for Myasthenia Gravis?

Answer 15

Muscular dystrophies, amyotrophic lateral sclerosis (ALS), progressive bulbar palsy, ophthalmoplegia of other causes, hyperthyroidism, and psychoneurotic asthenia.

Question 16

What are autonomic symptoms characteristic of Lambert-Eaton Syndrome?

Answer 16

Dry mouth, constipation, impotence, and hypohidrosis.

Question 17

What is the primary treatment for Lambert-Eaton Syndrome if associated with cancer?

Answer 17

Treatment of the underlying tumor, along with symptomatic management using pyridostigmine, IVIG, or 3,4-diaminopyridine.

Question 18

How can botulism be differentiated from other neuromuscular disorders?

Answer 18

: By the presence of descending symmetrical paralysis, absence of sensory changes, and EMG findings showing small, abnormal muscle action potentials.

Question 19

What are the side effects of guanidine hydrochloride, used in Lambert-Eaton Syndrome?

Answer 19

Bone marrow depression and cerebellar syndrome, including severe tremors.

Question 20

Q: What clinical response supports the diagnosis of Myasthenia Gravis?

Answer 20

A: Improvement in muscle strength following administration of cholinergic drugs such as pyridostigmine.

Question 21

Q: Why is thymectomy considered in Myasthenia Gravis management?

Answer 21

A: To remove abnormal thymus tissue (e.g., thymoma) that drives autoimmune responses against acetylcholine receptors.

Question 22

Q: What are the distinctive features of Myasthenic Crisis management?

Answer 22

A: Respiratory support, infection control, and gradual reintroduction of cholinergic therapy once stable.

Question 23

Q: How does repetitive nerve stimulation (RNS) differ in Myasthenia Gravis versus Lambert-Eaton Syndrome?

Answer 23

A: MG shows a decremental response, while LEMS shows an incremental response at high rates of stimulation.

Question 24

Q: What is the most common tumor associated with Lambert-Eaton Syndrome?

Answer 24

A: Small-cell carcinoma of the lungs.

Question 25

Q: How is plasmapheresis used in neuromuscular junction disorders?

Answer 25

A: To remove autoantibodies in cases like Myasthenia Gravis and Lambert-Eaton Syndrome for transient symptom relief.

Question 26

A 32-year-old woman presents with fluctuating weakness, especially in the evening, and difficulty keeping her eyelids open (ptosis). On physical examination, you notice weakness in ocular muscles, but her reflexes and sensation are normal. What diagnostic tests would confirm the diagnosis?

Answer 26

Antibody testing for acetylcholine receptor antibodies.
Electrophysiological studies, such as repetitive nerve stimulation (RNS) showing a decremental response.
Edrophonium (Tensilon) or neostigmine test demonstrating improvement in symptoms.

Question 27

: A 45-year-old man with a history of Myasthenia Gravis presents with severe dysphagia, respiratory distress, and generalized muscle weakness after a recent upper respiratory infection. What is the immediate management?

Answer 27

Initiate respiratory support (mechanical ventilation if needed).
Treat the underlying infection.
Temporarily hold cholinesterase inhibitors until the patient stabilizes to avoid cholinergic crisis.
Consider plasmapheresis or IVIG for rapid symptom management.

Question 28

A 60-year-old man with a history of smoking presents with proximal muscle weakness, dry mouth, and absent knee reflexes. He reports some improvement in strength after exercise. What condition do you suspect, and what test would confirm it?

Answer 28

Suspect Lambert-Eaton Myasthenic Syndrome (LEMS), commonly associated with small-cell lung cancer.
Perform EMG with repetitive nerve stimulation showing an incremental response at high stimulation rates

Question 29

A 50-year-old woman presents with ptosis, dysarthria, and generalized muscle weakness. Reflexes are preserved, and sensation is normal. What conditions should you consider and differentiate from?

Answer 29

Myasthenia Gravis: Check for antibody levels and RNS findings.
Hyperthyroidism: Assess thyroid function tests.
Lambert-Eaton Syndrome: Look for absent reflexes and autonomic symptoms.
Muscular dystrophies: Family history and genetic testing can help differentiate.

Question 30

A 40-year-old woman with Myasthenia Gravis is treated with pyridostigmine but develops diarrhea and abdominal cramps. What is the cause, and how would you manage it?

Answer 30

Cause: Muscarinic side effects of pyridostigmine.
Management: Administer atropine to alleviate muscarinic symptoms while continuing cholinesterase inhibitor therapy.