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Neuro > Myopathies > Flashcards

Myopathies Flashcards

1
Q

What is equine rhabdomyolysis ?

A

Muscle cramping or pain that occours usually during or following excercise

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2
Q

What are the 2 forms of equine rhabdomyolysis?

A

Acute (may require emergency Tx)

Between episodes in a horse with recurrent episodic attacks. Requires investigation of the cause

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3
Q

Clinical signs of exertional rhabdomyolysis

A

Stuff movements, pain, sweating, tachycardia, myoglobinuria

  • plasma CK and AST
  • r/o other dz
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4
Q

What does CK Stand for?

A

Creatine kinase (NOT creatinine)

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5
Q

How long after an acute exertional rhabdomyolysis episode do plasma levels of indicative hormones rise?

A

CK peaks at 6hrs, halved by 24hrs
AST peaks at 24hrs, takes longer to decrease
- if seeing a horse after the acute attack, have to r/o liver disease as AST will be the only thing raised

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6
Q

Tx acute rhabdomyolysis

A
  • Analgesics (opioids, probably avoid NSAIDs d/t risk of renal failure with myoglobinuria and NSAIDs combo
  • IV and oral fluids
  • diuretics (prevent or minimise nephrotoxic effects of myoglobin)
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7
Q

How can horses be investigated in between episodes?

A

Excercise test - 20 mins lunge excercise trot and canter

  • pre and 6 hour post excercise CK measurements
  • 100% rise regarded as significant but nothing magic about this number!
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8
Q

Acquired aetiology of exertional rhabdomyolysis

A

Over exertion
- eccentric contraction worse (downhill or jumping work)
- metabolic exhaustion
- oxidative injury
Eletrolyte imbalance
Hormone? Females affected worse than males
Infectious causes

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9
Q

What is DOMS

A

Delayed onset muscle spasm?

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10
Q

Inherited aetiology of exertional rhabdomyolysis

A

Recurrent exertional d/t defective calcium regulation

Polysaccharide storage myopathy

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11
Q

Which causes are more likely?

A

R/o acquired, but inherited more likely

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12
Q

what is RER ?

A

Recurrent exertional rhabdomyolysis

  • defect in calcium regulation that has been studied in detail in small group of related TB
  • other TBs affected the same defect?
  • similar disorder in other breeds?
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13
Q

Which horses is RER most common in?

A

Young nervous fillies

5% TBs affected!!

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14
Q

How can RER be prevented?

A

Oral dantrolene - calcium channel release blocker
- for TBs with presumed calcium homeostasis problem
High fat low carb diet
- rice bran, vegetable oil, commercial
Regular excercise and turnout

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15
Q

What is PSSM1?

A

Polysaccharide storage myopathy

  • 1 = the form with genetic mutation of glycogen synthase in skeletal muscle
  • affects QH, warmbloods and draft horses, cobs and many others
  • heritable autosomal dominant
  • causes exertional rhabdomyolysis
  • occasional muscle atrophy/weakness in draft breeds
  • abnormal glucose metabolism
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16
Q

Which breed is most commonly affected by PSSM1?

A

Belgian draft horses >50% carry dominant gene

- not necessarily clinically affected but would be microscopically affected

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17
Q

Alternative names for equine rhabdomyolysis syndrome?

A

Monday morning disease, set fast, azoturia, myoglobinuria, tying up

18
Q

What is the action of glycogen synthase?

A

forms 1-4 links between glucose monomores -> glycogen

19
Q

How can PSSM be detected? Is it always detectable?

A

> diagnosis by muscle biopsy
- internalised nuclei = non-specific sign of muscle damage
- polysacharide inclusions diagnositic
DNA test also available
- submit blood (EDTA) or hair pluck
- if no mutation detected but clinical sings present = PSSM 2

20
Q

What are polysaccharide inclusions and how are they detected?

A
  • muscle biopsy
  • amylase added to break down polysaccharide
  • should get rid of all pink staining material with PAS
  • in PSSM some pink amylase resistance polysaccharide remains in the muscle cells
21
Q

Tx and management of PSSM1?@

A

= RER

  • ^ fat, v carbohydrate diet
  • advise regular daily exercise
  • if necessary start with hand walking then increase gradually
22
Q

What is exhausted horse syndrome?

A
  • long rides, hot humid conditions, esp in unfit animals
  • endurance riding
  • 3d event
  • cross country/hunting
    > glycogen depletion from muscles
    > electrolyte loss from sweat
    > hypovolaemia
23
Q

Clinical signs of exhausted horse syndrome?

A
  • depression
  • dehrydration, anorexia, v thrirst
  • ^ RR ^ HR
  • pyrexia
  • poor sweating
  • poor jugular distencsion, ^ CRT, v pulse pressure
  • v gut sounds
  • lamnititis
  • muscle pain and stiffness
  • synchronous diaphragmatic flutter (esp. with hypocalcaemia)
24
Q

WHat is synchronous diaphragmatic flutter?

A

= Thumps

  • electrolyte imbalance esp. hypocalcaemia
  • phrenic nerve picks up depolarisation of the heart
  • rhythmical contraction in time with the heart
25
Q

Is rhabdomyolysis seen in dogs?

A

Yes, esp sled dogs and greyhounds (probably different aetiology between the two)

26
Q

What signs are seen in dogs with rhabdomyolysis

A
  • myoglobinuria
  • elevated CK
  • hyperthermia
  • renal failure
27
Q

Tx. exhausted horse syndrome?

A
  • IV/oral fluids + electrolytes
  • rapid cooling
  • NSAIDs
  • check for evidence rhabdomyolysis (CK and AST)
28
Q

Prevention exhausted horse syndrome?

A
  • trainaing, heat acclimitisation
  • free access to water
  • administer eletrolytes during the ride
  • frequent vet checks
29
Q

What is swimmer/limber/cold/rudder tail?

A
  • coccygeal muscle injury
  • working breeds labs pointers etc.
  • esp if swim a lot
  • recovery over several days
  • cold, exercise, swimming and prolonged cage transport predispose
30
Q

Tx rudder tail

A

rest, NSAIDs

31
Q

Look at physiology of muscle contraction

A
  • LMN
  • NMJ
  • T tubules
  • Na channels
  • Sarcoplasmic reticulum
  • Ryanodine
  • Reuptake of Calcium
32
Q

Give 3 examples of channelopathies

A
  1. Sarcolemmal sodium pump
    - Hyperkalaemic periodic paralysis in Quarter HOrses (HYPP)
    - autosomal dominant
    - all descending from “Impressive” QH sire, very impressive muscling, but had mutation in gene -> leaky Na influx and constant K+ outflow to compensate
    - hyperkamaeia -> cardiac arrhythmias
  2. Ryanodine Receptor (RYR1)
    - malignant hyperthermia in mixed breed dogs, Landrace pigs [PSE meat], QH
  3. Calcium ATPase [returns Ca to SR]
    - dysfunction -> permenant contraction
    - Brodie’s disease in humans
33
Q

Give an eg. of a cell signalling defect

A

> myostatin
TGFb protein , paracrine hormone that limits muscle growth
- mutations in Belgian Blue and Piedmontese cattle
-Bully whippets (heterozygotes run faster)
- Baby superman
- racehorses (depending on gene variation makes them better sprinters or endurance horses)

34
Q

What is muscle strain? How can muscle strain injuries progress to more severe disease?

A

> muscle strain: overstretching of muscle -> disruption of fibres
- inflammation, healing with fibrosis
- milkd - severe (complete rupture)
- recovery rapid with low grade injuries
- fibrous tissue may predispose to re-injury or contracture
- palpation oand ultrasound to diagnose
fibrotic myopathy in horses
- esp QH
- usually semitendinosius, sometimes semimembranosus or gracilis
- causes: Muscle tear, IM injection, neuropathy
- characteristic gait (slapping, short stride of affected limb) - do not confuse with Stringhalt

35
Q

Tx fibrotic neuropathy?

A
  • rest
  • NSAIDs
  • surgical resection fibrous tissue or tenotomy
36
Q

What is atypical myopathy?

A

Acute onset, severe myopathy in horses at pasture

    • CK and AST massively increased
  • muscle biopsy pre/post mortem (triceps/intercostals/diaphargam)
  • accumulation of lipid in cardiac/skeletal muscle
  • NOT exccercise induced
37
Q

Clinical signs of atypical myopathy?

A
  • myoglobinuria
  • cardiac arrhythmia
  • diaphragmatic failure
  • death
38
Q

Aetiology of atypical myopathy?

A

> Hypoglycin A
- sycamore tree
- unripe Ackee fruit (Jamaican national fruit)
- Box elder in US
- Acer species
Acyl co-a dehydrogenases inhibited by ‘MCPA’ metabolite
- important for breakdown of fat and uptake into the mitochondria

39
Q

Speciulative tx of atypical myopathy

A
  • riboflavin (Vit B2 supplement)
  • carnitine supplementation
  • support carbohydrate metabolism (?insulin/glucose CRI)
40
Q

Diagnosis of atypical myopathy?

A
  • muscle biopsy or urine/plasma acyl carnitine, organic acids, hypoglycin measurement
  • commercial test likely to become available
41
Q

Muscular dystrophies

A

Not gone into yet.. .

Neuro (30 decks)

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