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MNP - junctionopathy Flashcards

1
Q

What is the particularity of repetitive nerve stimulation in CHAT myasthenic syndrome?

A

High frequency conditioning train requires to observe decremental response

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2
Q

What is the key concept to differentiate focal from generalized myasthenia gravis?

A

Focal involve skeletal muscle group(s) that does not involve appendicular skeletal muscle
-> facial, esophageal, pharyngeal, and laryngeal skeletal muscles

Generalized involve appendicular skeletal muscle weakness, which can range from mild to severe, with or without facial, esophageal, pharyngeal, or laryngeal skeletal muscle involvement.

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3
Q

What are the 4 structures that can be implied in focal MG?

A

Following skeletal muscles:
Facial
Oesophageal
Pharyngeal
Laryngeal

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4
Q

What are the 4 subtypes of generalized MG?

A

Non-thymoma associated

Thymoma associated

Thiourylene medication associated (only cats)
- Carbimazole
- Methimazole
Reversible (excellent outcome)

Seronegative (only dogs)

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5
Q

What is the rate of one-year mortality in dogs with MG? Cats?

A

Dogs: 40-60%
Cats: 15%
In cats with generalized non-thymoma MG without megaoesophagus: 100% survival

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6
Q

What is the particularity for RNS in presynaptic CMS?

A

Preceding high frequency conditioning required before slow RNS to show decrement

A period of exercise is required before skeletal muscle weakness and fatigability: at that time, palpation can identify hypertonicity

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7
Q

What is the treatment of presynaptic CMS?

A

Guanidine
3,4-diaminopyridine (3,4-DAP)  increase Ach in synaptic cleft

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8
Q

What are the cause for false-negative MG?

A

Too early (no seroconversion)
Corticosteroids
Damage to the antigenic epitopes during solubilization
Majority of Ab bound in the skeletal muscle
Autoantibodies being direct against toxin binding site

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9
Q

What is the proportion of MG cats with megaoesophagus?

A

37-50%

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10
Q

Breeds predisposed to congenital myasthenia gravis

A

Springer spaniel
Jack Russell terrier
Miniature Dachshund (may regress spontanously at 6 months)
Samoyed
Smooth haired fox terrier (predisposed to concomitant megaesophagus)
Old danish pointing dog

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11
Q

What is the classification of congenital myasthenic syndromes and cite one mutation in each category ?

A

Presynaptic: CHAT
Synaptic: COLQ
Postsynaptic: CHRNE

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12
Q

What is the reaction catalyzed by creatine kinase?

A

ADP + phosphocreatine -> creatine + ATP

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13
Q

True or false: seronegative myasthenia gravis has been described in cats.

A

false

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14
Q

What are the 2 striational autoantibodies that can be found in dogs with myasthenia gravis?

A

Anti-titin receptors
Anti-ryanodine receptors

Attention: only in seropositive dogs for AChR, mainly non-thymoma associated, but also some thymoma-associated.
Not in cats!

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15
Q

True or false: Positive serum antibodies against AchR are found in thiourylene associated myasthenia gravis.

A

True

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16
Q

What is the incidence of a concurrent cranial mediastinal mass in dogs and cats with MG?

A

Dogs: 3.4%
Cats: 52%

17
Q

In which congenital myasthenic syndrome AChE inhibitors cannot be used ? What is a proposed treatment?

A

COLQ
Albuterol (beta2 adrenergic receptor agonist) -> stabilize NMJ and decrease AChR dispersion
Note: 3,4-DAP and AChE-I worsen signs

18
Q

What are the conditions to evoke seronegative myasthenia gravis?

A

General and neurological examination, pharmacologic, and electrophysiologic findings consistent with MG
Normalization of clinical signs after AChE-I treatment
Serum AChR autoantibody testing by radioimmunoassay to have been negative at least twice.

19
Q

For each congenital myasthenic syndrome in dogs and cats, give: affected NMJ component, mechanism of defect, protein, gene, species/breeds.

A

Presynaptic
Defect in ACh synthesis
ChAT = choline acetyltransferase
CHAT
Dogs: Old Danish Pointing dogs

Synaptic
AChE deficiency
Collagen-like tail subunit of asymmetric AChE
COLQ
Dogs: Labrador, Golden – Cats: Devon Rex, Sphynx

Postsynaptic
AChR deficiency
Acetylcholine receptor subunit epsilon
CHRNE
Dogs: Jack Russell Terrier, Heideterrier

20
Q

What are the specific features of COLQ mutation in cats compared to dogs?

A

Later onset (3-23 weeks vs. 2-8 weeks in dogs)
Decrease skeletal muscle mass
Dorsal protrusion of scapulae
EMG changes (PSW, CRD)
RNS can be within normal limits
Dystrophic changes
Normal postsynaptic AChR concentration

21
Q

cite drugs that can alter neuromuscular function

A

Lidocaine, gentamicin
Procaine, metronidazole
Tetracyclines

22
Q

Which are the 2 positive and 2 negative factors associated with clinical remission in dogs with MG?

A

Positively associated with clinical remission
Younger age
Comorbid endocrine disease

Negatively associated with clinical remission
Initial AChR Ab concentration
Regurgitation

No clinical improvement: 29%

23
Q

AchR are permeable to

A

Na+ and K+

24
Q

% megaoesophagus in aquired myasthenia gravis in dog

A

dog: 90%
rare in congenital form

25
Q

breed with congenital myasthenia with spontaneous remission
and with good prognosis

A

smooth haired miniature dashund

Devon Rex and Jack can survive years

26
Q

Post synaptic congenital myasthenia gravis

A

Jack Russel
mut CHRNE (cholinergic recept nicot epsilon
onset 6-8w
decrement, dim AchR

improvement with AchE inhib but dev resistance

Heideterrier < 1w affected initially TL

27
Q

synaptic congenital myasthenia gravis

A

Labrador, Golden, Sphinx, devon Rex

mut acetylcholinesterase (COLQ). Onset 2-3w. Decremental resp, marginaly decrease AchR. Worsening with pyridostigmine/edrophoium.

Improvement in Golden with albuterol. (bet2ago)

In cat musc atrophy, protrusion scapulae, PSW and complex rep discharge at EMG. Dystrophic change in m biopsy, normal AchR.

28
Q

presynaptic congen myasthenia gravis

A

Old Danish Pointing dog (Gammel Dansk Honsehunds)
mutation choline acetyltransferase (CHAT) -> synthesis of ACh.

Onset 12-16w.
decrement only after high freq stim.

Treat: guanidine in human 3,4-DAP (diaminopyridine)
no improvement with AchEi

29
Q

treatment associated with myasthenia gravis devt

A

methimazole (antib AchR

29
Q

diagnosis myasthenia gravis
% seronegative dog

A

immunoprecipitation radioimmunoassay ab anti AchR
can be normalised with 1 w corticoids
2% seroneg

edrophonium chloride test/neostigmine methylsulfate

decrement, single fiber electromyography

30
Q

treatment and % remission dog myasthenia

A

pyridostigmide bromide, neostigmine bromide

89% remission at an average 6m

31
Q

cat/dog breeds predisposed to myasthenia

A

cat: Somali
Abyssian

dog: Akita, Sccottish terrier, german shorthaired pointer, Chihuahua

32
Q

% cranial mediastinal mass in cat with aquired myasthenia gravis

A

52%
98% tymoma 2% lymphoma
clinical outcome not associated with presence mass
clinical outcome did not differ between surgical or medical treat

33
Q

factors associated with clinical remission of myasthenia

A

younger age
comorbid endocrine disease

negativ ass: initial AchR ab concent, regurgitation

34
Q
A

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