Neuromuscular Disorders

Question 1

What is Myasthenia Gravis (MG)?

Answer 1

MG is an autoimmune neuromuscular junction disorder characterized by muscle weakness and fatigability due to autoantibodies against acetylcholine receptors.

Question 2

What are the two major neuromuscular disorders covered in this document?

Answer 2

Myasthenia Gravis and Muscular Dystrophy.

Question 3

What is the pathophysiology of Myasthenia Gravis?

Answer 3

Autoantibodies attack acetylcholine receptors at the neuromuscular junction, reducing signal transmission and causing muscle weakness.

Question 4

What are the three components of the neuromuscular junction?

Answer 4

Presynaptic membrane, synaptic cleft, and postsynaptic membrane.

Question 5

What percentage of MG patients have anti-acetylcholine receptor (AChR) antibodies?

Answer 5

80-90% of generalized MG and 50-60% of ocular MG cases.

Question 6

What is seronegative MG?

Answer 6

MG in which patients lack detectable AChR antibodies, often associated with MuSK antibodies.

Question 7

What thymic abnormalities are common in MG?

Answer 7

Thymic hyperplasia (70%) and thymoma (10%).

Question 8

What is the main clinical feature of MG?

Answer 8

Muscle weakness that worsens with activity and improves with rest.

Question 9

Which muscles are most commonly affected in MG?

Answer 9

Extraocular muscles, bulbar muscles, neck, and shoulder girdle muscles.

Question 10

What is the first symptom in most MG patients?

Answer 10

Ptosis (drooping eyelid) and diplopia (double vision).

Question 11

How does MG affect bulbar muscles?

Answer 11

It causes dysphagia (difficulty swallowing) and dysphonia (voice changes).

Question 12

What is the Osserman classification for MG severity?

Answer 12

0 - Asymptomatic, 1 - Ocular symptoms, 2 - Mild generalized weakness, 3 - Moderate generalized weakness/bulbar involvement, 4 - Severe generalized weakness/respiratory dysfunction.

Question 13

What is Lambert-Eaton Myasthenic Syndrome (LEMS)?

Answer 13

A presynaptic disorder of neuromuscular transmission affecting voltage-gated calcium channels, often associated with small cell lung cancer.

Question 14

How does botulism affect neuromuscular transmission?

Answer 14

It blocks acetylcholine release, leading to paralysis and affecting pupillary responses.

Question 15

What is the Tensilon test?

Answer 15

A test using edrophonium chloride (a short-acting acetylcholinesterase inhibitor) to temporarily improve muscle strength in MG.

Question 16

What is the Ice-Pack Test?

Answer 16

A test where an ice pack is placed over the eyelid to improve ptosis in MG patients.

Question 17

Which antibodies are found in MuSK-associated MG?

Answer 17

Muscle-specific tyrosine kinase (MuSK) antibodies.

Question 18

What is the gold standard electrophysiologic test for MG?

Answer 18

Single Fiber EMG (SFEMG), which detects increased jitter and neuromuscular transmission defects.

Question 19

Why should MG patients undergo chest imaging?

Answer 19

To check for thymoma or thymic hyperplasia.

Question 20

What is the first-line treatment for ocular MG?

Answer 20

Anticholinesterase inhibitors like pyridostigmine or neostigmine.

Question 21

What is the first-line treatment for generalized MG?

Answer 21

Corticosteroids (prednisolone) with or without immunosuppressants like azathioprine or mycophenolate mofetil.

Question 22

What is the role of thymectomy in MG?

Answer 22

Thymectomy is recommended for patients with thymoma and can improve outcomes in non-thymomatous generalized MG.

Question 23

What are the triggers for Myasthenic Crisis?

Answer 23

Respiratory infections, stress, surgery, pregnancy, and certain medications (aminoglycosides, beta-blockers).

Question 24

What is Myasthenic Crisis?

Answer 24

An acute exacerbation of MG leading to severe weakness of respiratory and upper airway muscles, requiring ventilatory support.

Question 25

How is Myasthenic Crisis managed?

Answer 25

Intubation, plasmapheresis, or intravenous immunoglobulins (IVIG).

Question 26

What is a Cholinergic Crisis?

Answer 26

Excessive acetylcholinesterase inhibitor use causing continuous depolarization, leading to weakness and autonomic symptoms like salivation and diarrhea.

Question 27

How is a Cholinergic Crisis differentiated from a Myasthenic Crisis?

Answer 27

The edrophonium test improves Myasthenic Crisis but worsens Cholinergic Crisis.

Question 28

What are neuromuscular blocking agents that worsen MG?

Answer 28

Succinylcholine and non-depolarizing muscle relaxants (e.g., vecuronium).

Question 29

What is Muscular Dystrophy?

Answer 29

A group of genetic disorders causing progressive muscle weakness due to defective muscle proteins.

Question 30

What is the most common type of Muscular Dystrophy?

Answer 30

Duchenne Muscular Dystrophy (DMD).

Question 31

What is the genetic cause of Duchenne Muscular Dystrophy?

Answer 31

Mutations in the dystrophin gene on the X chromosome.

Question 32

What is the difference between Duchenne and Becker Muscular Dystrophy?

Answer 32

DMD has little to no dystrophin, while BMD has reduced but functional dystrophin.

Question 33

What is Gower's Sign?

Answer 33

A sign of proximal muscle weakness where patients use their hands to push on their legs to stand up.

Question 34

What is the inheritance pattern of Duchenne Muscular Dystrophy?

Answer 34

X-linked recessive.

Question 35

What are the common types of Muscular Dystrophies?

Answer 35

Duchenne, Becker, Limb-Girdle, Facioscapulohumeral, and Myotonic Dystrophy.

Question 36

What are early symptoms of Duchenne Muscular Dystrophy?

Answer 36

Delayed motor milestones, difficulty climbing stairs, frequent falls, and calf pseudohypertrophy.

Question 37

What is the main cause of death in Duchenne Muscular Dystrophy?

Answer 37

Respiratory failure or cardiomyopathy.

Question 38

What is the main diagnostic test for Duchenne Muscular Dystrophy?

Answer 38

Genetic testing for dystrophin mutations.

Question 39

Which enzyme is elevated in Duchenne Muscular Dystrophy?

Answer 39

Creatine Kinase (CK).

Question 40

What is the treatment for Duchenne Muscular Dystrophy?

Answer 40

Corticosteroids (prednisolone), physical therapy, and supportive care.

Question 41

What are common complications of Muscular Dystrophy?

Answer 41

Scoliosis, respiratory failure, cardiac dysfunction, and contractures.

Question 42

What is Myotonic Dystrophy?

Answer 42

A muscular dystrophy characterized by progressive weakness and myotonia (delayed muscle relaxation).

Question 43

What are the systemic features of Myotonic Dystrophy?

Answer 43

Cataracts, cardiac conduction defects, insulin resistance, and cognitive impairment.

Question 44

What is the most common adult-onset Muscular Dystrophy?

Answer 44

Myotonic Dystrophy Type 1 (DM1).

Question 45

How is Muscular Dystrophy managed?

Answer 45

Supportive care, corticosteroids, physical therapy, and assistive devices.

Question 46

What are some genetic mutations associated with Limb-Girdle Muscular Dystrophy?

Answer 46

Dysferlin, sarcoglycan, and calpain mutations.

Question 47

How is Facioscapulohumeral Muscular Dystrophy inherited?

Answer 47

Autosomal dominant.

Question 48

What is the prognosis of Duchenne Muscular Dystrophy?

Answer 48

Patients often require wheelchairs by their teens and have a reduced lifespan, usually due to respiratory or cardiac failure.

Question 49

How does Becker Muscular Dystrophy differ in prognosis?

Answer 49

Becker Muscular Dystrophy has a later onset and milder progression compared to Duchenne.