38. Neuromuscular junction diseases Flashcards Preview

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Flashcards in 38. Neuromuscular junction diseases Deck (23):
1

2 neuromascular junction diseases

1. myasthenia gravis
2. Lambert- Eaton myasthenic syndrome

2

MC neuromascular junction disorder

myasthenia gravis

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myasthena gravis vs Lambert - Eaton according frequency

1. myasthenia gravis --> MC uromascular junction disorder
2. Lambert- Eaton ---> uncommon

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pathophysiology of myasthenia gravis

autoantibodies to postsynaptic Ach receptor

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pathophysiology of Lambert - Eaton myasthenic syndrome

autoantibodies to postsynaptic Ach receptor

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Pathophysiology of Lambert-Eaton myasthenic syndrome

autoantibodies to presynaptic Ca2+ channel --.> decreased Ach release

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myasthenia gravis is associated with

1. thymmoma
2. thymic hyperplasia

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Lambert - Eaton mysthenic syndrome is associated with

small cell lung cancer ( paraneoplastic syndrome )

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myasthenia gravis - sex

MC seen in women

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myasthenia gravis vs Lamber - Eaton - eyes involvement

1. myasthenia gravis --> classically involves eyes
2. Lambert- Eaton --> eyes are usually spared

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myasthenia gravis - symptoms

1. ptosis
2. diplopia
3. weakness
worsen with muscle use

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Lambert- Eaton myasthenic syndrome - symptoms

1. proximal muscle weakness
2. autonomic symptoms ( dry mouth, impotence)
imporoves with muscle use

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autonomic symptoms of Lambert- Eaton myasthenic syndrome

dry mouth, impotence

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myasthenia gravis vs Lambert- Eaton - symptoms after muscle use

1. myasthenia gravis --> reversal of symptoms
2. Lambert-Eaton --> minimal effect

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• Symptoms of myasthenia gravis ____ (improve/worsen) with muscle use; symptoms of Lambert-Eaton syndrome ____ (improve/worsen) with use.

Worsen; improve

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• A young female patient has ptosis, diplopia, and weakness that worsens with muscle use. What is the root cause of her symptoms?

Autoantibodies to postsynaptic acetylcholine receptors (the patient likely has myasthenia gravis)

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• Name the two ophthalmic manifestations of myasthenia gravis.

Ptosis and diplopia

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• A young female has ptosis, diplopia, and weakness that worsens with muscle use. Why do you want to order a chest X-ray on her?

Because of its strong association with myasthenia gravis, patients with this diagnosis should be screened for a thymoma

19

• A patient has dry mouth and proximal muscle weakness that improves with muscle use. What is the root cause of her symptoms?

Autoantibodies to presynaptic calcium channels, causing decreased acetylcholine release (the patient has Lambert-Eaton myasthenic syndrome

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• Lambert-Eaton myasthenic syndrome leads to ____ (proximal/distal) muscle weakness.

Proximal

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• A man has autoantibodies against presynaptic calcium channels, causing weakness. What malignancy is his disease classically associated with?

Small cell lung cancer (he has Lambert-Eaton myasthenic syndrome)

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• Do myasthenia gravis and Lambert-Eaton syndrome both improve with acetylcholinesterase inhibitor use?

No, as only myasthenia gravis reverses with the use of AChE inhibitors, whereas Lambert-Eaton syndrome does not

23

• A smoker presents with proximal muscle weakness, dry mouth, and impotence. Administration of an AChE inhibitor has no effect. Diagnosis?

Lambert-Eaton myasthenic syndrome (likely secondary to small cell lung cancer)

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