IIB1g - Neoplasia of PNS and Neuromuscular Flashcards

(24 cards)

1
Q

What are three proposed mechanisms by which paraneoplastic neuropathies may arise?

A

1) Neurotoxic factors released by the tumor

2) Disruption of axons and/or schwann metabolism

3) Immunologic reaction to antigens shared by the tumor and the peripheral nerves

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2
Q

Which chemotherapeutic has been known to result in neuropathies?

A

Vincristine

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3
Q

Name four neoplasias that are known to cause paraneoplastic neuropathies?

A

1) Insulinoma
2) Carcinoma
3) Melanoma
4) Lymphoma

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4
Q

What is the pathogenesis behind the paraneoplastic polyneuropathy caused by insulinoma and how does this differ from the CNS effects?

A

Signs are due to a necrotizing neuropathy

The peripheral nerve system is resistant to the effects of hypoglycemia which is normally the source of CNS signs

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5
Q

What percentage of malignant nerve sheath tumors arise in the nerve root near to the spinal cord?

A

about 45%

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6
Q

Malignant nerve sheath tumors arise most commonly within what group of nerves?

A

The nerves of the brachial plexus

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7
Q

Ultrasound may be able to ID a malignant nerve sheath tumor in what % of cases?

A

55%

The same % as MNST found distal to the nerve roots

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8
Q

What is the most common cranial nerve to be affected by mononuclear cells neoplasias?

A

Cranial nerve V

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9
Q

Multicentric lymphoma may affect the peripheral nerves in what two ways?

A

1) Direct invasion of the nerve
2) Paraneoplastic effects on the nerve

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10
Q

Lymphosarcoma in some cases may result in what type of pleocytosis on CSF?

A

Lymphocytic

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11
Q

In acquired myasthenia gravis, antibodies are formed against what structure?

A

The nicotinic acetylcholine receptors

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12
Q

What percentage of dogs with a thymoma, develop acquired myasthesia gravis?

A

~ 17 %

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13
Q

Which two cat breeds are predisposed to acquired myasthenia gravis?

A

Abyssinian
Somali

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14
Q

What dog breeds are at higher than average risk for acquired myasthenia gravis?

A

Akitas
Severeal terrier breeds
German shorthair pointers
Chihuahua

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15
Q

Which dog breeds have a higher absolute mortality if they acquired myasthenia gravis?

(not necessarily having a higher risk of getting it, just a higher risk of death)

A

Golden retrievers
German shepherd dogs

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16
Q

A fatigue-able palpebral is a clinical sign of myasthenia gravis which is more commonly seen in which species?

17
Q

What are the three forms of acquired myasthenia gravis?

A

1) Focal
2) Generalized
3) Acute fulminant

18
Q

What % of dogs show focal signs of acquired myasthenia gravis?

19
Q

What % of cats show focal signs of acquired myasthenia gravis?

20
Q

Why is megaesophagus much less commonly seen in cats with acquired myasthenia gravis than dogs?

A

Cats have a higher proportion of smooth muscle in their esophagus compared with dogs

Dogs = entirely striated muscle; Cats = caudal 1/3 is smooth muscle

21
Q

Which two repetitions should be compared when performing a repetitive nerve stimulation (RNS) for screening for acquired myasthenia gravis?

A

Reps 1 and 5 should be compared

A decrement of more than 10% is supportive of myasthenia gravis

22
Q

What is the most sensitive test for all forms of acquired myasthesia gravis?

A

Acetylcholine receptor antibody titer

92-100% sensitive

23
Q

What test can be performed in patients with seronegative myasthenia gravis in order to confirm a diagnosis?

A

Muscle biopsy with IHC

Horse radish peroxidase (not specific tot he AB from myasthenia though)

24
Q

How likely is acquired myasthenia gravis to resolve in patients that have a surgically removed thymoma vs surgically removed thymic hyperplasia?

A

Removal of thymic hyperplasia usually improved MG signs

Removal of a thymoma usually does not result in improvement