IIB1g - Neoplasia of PNS and Neuromuscular Flashcards
(24 cards)
What are three proposed mechanisms by which paraneoplastic neuropathies may arise?
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
Which chemotherapeutic has been known to result in neuropathies?
Vincristine
Name four neoplasias that are known to cause paraneoplastic neuropathies?
1) Insulinoma
2) Carcinoma
3) Melanoma
4) Lymphoma
What is the pathogenesis behind the paraneoplastic polyneuropathy caused by insulinoma and how does this differ from the CNS effects?
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
What percentage of malignant nerve sheath tumors arise in the nerve root near to the spinal cord?
about 45%
Malignant nerve sheath tumors arise most commonly within what group of nerves?
The nerves of the brachial plexus
Ultrasound may be able to ID a malignant nerve sheath tumor in what % of cases?
55%
The same % as MNST found distal to the nerve roots
What is the most common cranial nerve to be affected by mononuclear cells neoplasias?
Cranial nerve V
Multicentric lymphoma may affect the peripheral nerves in what two ways?
1) Direct invasion of the nerve
2) Paraneoplastic effects on the nerve
Lymphosarcoma in some cases may result in what type of pleocytosis on CSF?
Lymphocytic
In acquired myasthenia gravis, antibodies are formed against what structure?
The nicotinic acetylcholine receptors
What percentage of dogs with a thymoma, develop acquired myasthesia gravis?
~ 17 %
Which two cat breeds are predisposed to acquired myasthenia gravis?
Abyssinian
Somali
What dog breeds are at higher than average risk for acquired myasthenia gravis?
Akitas
Severeal terrier breeds
German shorthair pointers
Chihuahua
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)
Golden retrievers
German shepherd dogs
A fatigue-able palpebral is a clinical sign of myasthenia gravis which is more commonly seen in which species?
Cats
What are the three forms of acquired myasthenia gravis?
1) Focal
2) Generalized
3) Acute fulminant
What % of dogs show focal signs of acquired myasthenia gravis?
About 40%
What % of cats show focal signs of acquired myasthenia gravis?
About 15 %
Why is megaesophagus much less commonly seen in cats with acquired myasthenia gravis than dogs?
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
Which two repetitions should be compared when performing a repetitive nerve stimulation (RNS) for screening for acquired myasthenia gravis?
Reps 1 and 5 should be compared
A decrement of more than 10% is supportive of myasthenia gravis
What is the most sensitive test for all forms of acquired myasthesia gravis?
Acetylcholine receptor antibody titer
92-100% sensitive
What test can be performed in patients with seronegative myasthenia gravis in order to confirm a diagnosis?
Muscle biopsy with IHC
Horse radish peroxidase (not specific tot he AB from myasthenia though)
How likely is acquired myasthenia gravis to resolve in patients that have a surgically removed thymoma vs surgically removed thymic hyperplasia?
Removal of thymic hyperplasia usually improved MG signs
Removal of a thymoma usually does not result in improvement
