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Neurology > Acquired and Genetic Myopathies > Flashcards

Acquired and Genetic Myopathies Flashcards

1
Q

Define rhabdomyolysis

A

Lysis of muscle fibres

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2
Q

When does equine rhabdomyolysis syndrome typically occur?

A

During or following exercise

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3
Q

What is equine rhabdomyolysis syndrome also known as?

A 
Monday Morning Disease
Set-fast
Azoturia
Myoglobinuria
Tying-up
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4
Q

How might horses with equine rhabdomyolysis syndrome present?

A

As an acute emergency

Between episodes in horse that suffer multiple episodes

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5
Q

How can you diagnose equine rhabdomyolysis syndrome during an episode?

A

Clinical signs
Measure CK and AST levels
- CK increases very quickly but also fades quickly

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6
Q

What clinical signs do you seen during an episode of equine rhabdomyolysis syndrome?

A 
Stiff movements
Pain
Sweating
Tachycardia
Myoglobinuria
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7
Q

What may you see in the urine of a horse with equine rhabdomyolysis syndrome?

A

Myoglobinuria

Renal tubular casts (Formed due to the nephrotoxic effects of myoglobin)

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8
Q

How would you treat acute equine rhabdomyolysis syndrome?

A

Analgesia (NSAIDs/opiates)
IV fluids (if severe)
Diuresis (Flush nephrotoxic myoglobin)
Dantrolene (?) - muscle relaxant inhibiting Ca ions From sarcoplasmic reticulum

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9
Q

How would you diagnose a horse with equine rhabdomyolysis syndrome if it presents between episodes?

A

Exercise test

  • Measure CK
  • 20 minutes lung in trot
  • 6 hours later measure CK
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10
Q

What rise in CK levels could be considered significant and an indicator of equine rhabdomyolysis syndrome?

A

> 100% increase

But up to 20% may be signifcant

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11
Q

List some acquired aetiologies of equine rhabdomyolysis syndrome

A
  • Overexertion
    + Eccentric contraction (Going downhill, sudden changes in movements)
    + Metabolic exhaustion (Cannot make ATP so degenerates)
    + Oxidative injury (due to exercising in heat)
  • Electrolyte imbalance
  • Hormonal influence
  • Infectious causes
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12
Q

List some inherited aetiologies of equine rhabdomyolysis syndrome…

A

Recurrent exertional equine rhabdomyolysis syndrome due to defective calcium regulation
Polysaccharide storage myopathy

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13
Q

How should you work up a case of repeated equine rhabdomyolysis syndrome in a horse?

A
  • Rule out acquired causes

- Inherited causes are more likely - check for these once acquired causes are ruled out

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14
Q

Describe the relationship between acquired and inherited causes of repeated episode of equine exertional rhabdomyolysis…

A

Some acquired causes (e.g. overexertion) can cause an attack in a genetically-susceptible animal

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15
Q

Which breed of horse is suspectible to recurrent exterional rhabdomyolysis?

A

Thoroughbreds - 5% of population

Most common in young nervous fillies

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16
Q

How would you prevent recurrent exertional rhabdomyolysis?

A
  • Oral dantrolene
    + Ca2+ release channel blocker
    + Prescribed to TBs with a presumed calcium homeostasis issue
  • High fat low carb diet
    + Rice bran, vegetable oil, commercial diet
  • Regular exercise/turn out
    + Balance turning out and weight control
    + If they end up grazing all day they’ll get fat
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17
Q

Which breeds are predisposed to PSSMI - polysaccharide storage myopathy?

A 
Quarter horses
Warmbloods
Draft horses
Cobs
Many others
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18
Q

How does polysaccharide storage myopathy cause exterional myopathy?

A
  • Heritable - autosomal dominant
  • Causes a mutation in glycogen synthase gene in skeletal muscle
    + No more 1-4 links between glucose monomers
    + Abnormality of glycogen metabolism
    + Muscle atrophy/weakness
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19
Q

How can you test for PSSMI?

A

DNA
- Hair pluck or EDTA blood
Muscle biopsy

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20
Q

How can you treat and manage PSSMI?

A
  • High fat, low carb diet
  • Regular daily exercise
    + Start with hand walking and increase gradually every day
  • Try to reverse the damage we do by keeping them all pampered and all
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21
Q

What is ‘The Exhausted Horse’?

A

A horse that is exhausted
usually after a long ride in hot and humid, especially in unfit horses
+ endurance rides
+ three day eventing
+ hunting
results in glycogen depletion from muscles, electrolyte loss from sweat, and hypovolaemia

22
Q

What are the clinical signs of the exhausted horse?

A 
Depression
Dehydration, anorexia, thirst
Increased RR and HR
Pyrexia
Poor sweating response
Poor jugular distension, increased CRT and decreased pulse quality
Decreased gut sounds
Laminits
Synchronous diaphragmatic flutter
Muscle pain and stiffness
23
Q

What is a synchronous diaphragmatic flutter?

A

AKA THUMPS
When the phrenic nerve picks up the electrical impulse of the heart and causes contraction
like hiccups! This is due to electrolyte abnormalities in metabolic exhaustion. Characteristic but not seen everytime in exhausted horse

24
Q

How would you treat the exhausted horse?

A 
IV/Oral fluids 
Rapid cooling
NSAIDs
Check for rhabdomyolysis
- CK and AST
25
Q

How can you prevent the exhausted horse syndrome?

A

Training
Heat acclimatisation
Free access to water and electrolyte supplements
Frequent veterinary checks

26
Q

Which dog breeds are you likely to see exertional rhabdomyolysis in?

A

Greyhounds

Sled dogs

27
Q

What does exertional rhabdomyolysis cause in dogs?

A

Renal failure
Myoglobinuria
Elevated CK
Hyperthermia

28
Q

Which dogs are predisposed to coccygeal muscle injury?

A

Working breeds
Really happy dawgs
Exercise, swim or transported for long time in cage

29
Q

What do you see in a dog with a coccygeal muscle injury?

A

Pain at the tail base

Mild elevated CK

30
Q

How would you treat coccygeal muscle injury in dogs?

A

Let them rest for several days

NSAIDs

31
Q

Name three types of channelopathies…

A

Sarcolemmal sodium pump
Ryanodine receptor
Calcium ATPase

32
Q

What would you see in an animal with a sarcolemmal sodium pump channelopathy?

A

Hyperkalaemic periodic paralysis in quarter horses
+ as the concentration of K+ increases
Muscle fasciculations
Especially in horses with huge muscles

33
Q

What would you see in an animal with a ryanodine receptor channelopathy?

A 
This receptor is involved in calcium release from the sarcoplasmic reticulum
Malignant hyperthermia in:
- Landrace pigs
- Quarter horses
- Mixed breed dogs
34
Q

What would you see in an animal with a calcium ATPase channelopathy?

A

Congenital pseudomyotonia in cattle

35
Q

What cell signalling defect can cause a myopathy?

A

Defect of myostatin - grow uncontrolled muscle

36
Q

Which animals may you see a myostatin mutation in?

A

Belgian blue cattle
Bully whippets
Race horses

37
Q

What is a muscle strain injury?

A

Overstretching of muscle leading to disruption of muscle fibres leading to inflammatory and the muscle heals with fibrosis

38
Q

What is the prognosis in a muscle strain injury?

A

Mild - Rapid recovery

Sever - Reinjury possible

39
Q

Which muscle are you likely to see fibrotic myopathy in quarter horses?

A

Semitendinosus

Semimembranosus

40
Q

What causes fibrotic myopathy?

A

IM injections
Muscle tear
Neuropathy

41
Q

How would you treat a horse with fibrotic myopathy?

A

Rest
NSAIDs
Surgical resection

42
Q

What gait abnormalities would you see in a horse with fibrotic myopathy?

A

Slaps foot down when walking

Characteristic

43
Q

What is atypical myopathy?

A

Acute onset severe myopathy of horses at pasture

44
Q

What clinical signs would you see in a horse with atypical myopathy?

A

Weakness
+ May not be able to stand or lift their head
Heart problems
Rhabdomyolysis

45
Q

How would you diagnose a horse with atypical myopathy?

A

Increased CK and AST levels

Muscle biopsy pre/post mortem

46
Q

What causes atypical myopathy?

A

Issues with acyl CoA dehydrogenase resulting in no metabolism of fats for oxidative phosphorylation leads to no ATP. This is the result of ingestion of sycamore seeds which contains hyoglycin A which inhibits acyl CoA dehdrogenase

47
Q

How would you treat a horse with atypical myopathy?

A 
Riboflavin 
\+ Vitamin B2 supplement
Carnitine supplement
Support carbohydrate metabolism
\+ Insulin/glucose
48
Q

Which molecules do muscular dystrophies target?

A

Dystroglycans

Dystrophin

49
Q

Describe the pathology of muscular dystrophies…

A

Inflammation in muscle and macrophage infiltrate

Stem cells are activated post degeneration and cause regeneration

50
Q

How is muscular dystrophy diagnosed?

A

IHC

Neurology (12 decks)

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