Neuromuscular disorders

Question 1

Myopathies typically present with weakness and numbness in a (proximal/distal) distribution?

Answer 1

Proximal

Question 2

Neuromuscular junction pathologies typically present with weakness, numbness and fatiguability in a (proximal/distal) distribution?

Answer 2

Proximal + eyes

Question 3

Neuropathies typically present with weakness and numbness in a (proximal/distal) distribution?

Answer 3

Distal (Glove and stocking distribution)

Question 4

Duchenne muscular dystrophy is a inherited myopathy due to a mutation in the ____________ gene on the ___ chromosome?

Answer 4

Dystrophin gene on X chromosome

Question 5

What is the inheritance pattern of Duchenne Muscular Dystrophy?

Answer 5

XLR

Question 6

How does death usually occur in patients with Duchenne Muscular Dystrophy?

Answer 6

Progressive weakness of muscles
- including heart and respiratory → cardiac/respiratory failure/ chest infection/asphyxiation

Question 7

What is the physiological role of dystrophin?

Answer 7

Connects sarcomeres to sarcolemma and ECM → structural stability

Question 8

What is the pathogenesis of Duchenne Muscular Dystrophy?

Answer 8

Dystrophin mutation on X chromosome → dystrophin not tethered to sarcolemma

Muscle contraction → shear force → rips in sarcolemma → muscle breakdown + scarring

Question 9

What are 2 main treatment modalities for patients with Duchenne Muscular Dystrophy?

Answer 9

1) Corticosteroids
2) Gene replacment therapy

Question 10

What are 2 examples of inflammatory myopathies

Answer 10

1) Polymyositis
2) Dermatomyositis

Question 11

What are 2 causes of toxic myopathies?

Answer 11

1) Statins
2) Alcohol

Question 12

What are 3 conditions in which myopathy is a secondary presentation?

Answer 12

1) Lupus
2) Hypothyroidism
3) Critical illness myopathy

Question 13

What are 2 examples of metabolic myopathies?

Answer 13

1) Pompe disease (enzymatic deficiencies
2) Glycogen storage diseases

Question 14

What are 2 examples of mitochondrial myopathies?

Answer 14

1) MERRF
2) MELAS

Question 15

Myasthenia gravis is a autoimmune-mediated neuromuscular junction disorder in which the body produces antibodies against ____________.

Answer 15

Acetylcholine receptors

Question 16

What is the pathophysiology of worsening weakness and fatigability with sustained contraction in myasthenia gravis?

Answer 16

Initial release of ACh → overcome competitive inhibition of AChRAbs → strong contraction

Sustained contraction → progressive loss of native ACh by synaptic reuptake and breakdown → AChRAbs take over → fatigability

Question 17

Why is edrophonium (ACEi) not used clinically anymore?

Answer 17

1) Dangerous (can cause bradycardia and asystole)
2) Not HSA approved