Lame - Equine muscle disorders

Question 1

What can you assess on clinical exam for equine muscle disorders?

Answer 1

Degree and symmetry
Firmness

Question 2

What causes rapid muscle atrophy?

Answer 2

Neurogenic atrophy

Question 3

What does a base narrow stance indicate?

Answer 3

Weakness - elephant on a tub

Question 4

What are the main two muscle enzymes?

Answer 4

Creatine kinase
AST

Question 5

What is the kinetic for CK?

Answer 5

Peaks at 4-6 hours
Rises higher but reduces quicker

Question 6

What is the kinetics for AST?

Answer 6

Peaks at 24 hours, but takes a couple of weeks to return to normal

Question 7

What does it mean if both CK and AST are high?

Answer 7

Muscle damage - happened over 24 hours ago

Question 8

What does it mean if CK is high but AST is normal?

Answer 8

Acute muscle damage

Question 9

What does it mean if CK is normal but AST is very high?

Answer 9

Two weeks after known case of muscle damage

Question 10

What does it mean if CK is normal and AST is slightly elevated?

Answer 10

Red herring - AST is not muscle wastage specific, can mean liver damage too

Question 11

What can cause dark coloured urine in horses?

Answer 11

Myoglobinuria

Question 12

Why would there by myoglobin in the urine?

Answer 12

From break down of muscle cells

Question 13

What can myoglobinuria cause?

Answer 13

Nephrotoxic - acute renal failure

Question 14

When is myoglobinuria seen?

Answer 14

Typically only in severe rhabdomyolysis cases

Question 15

Where do you do a muscle biopsy in horses?

Answer 15

Semimembranosus
Tail head for equine motor neurone disease

Question 16

What method do you use for an equine muscle biopsy? What needle?

Answer 16

Bergstrom needle
Open method

Question 17

What are the big two myopathies?

Answer 17

Exercise associated myopathies
Atypical myopathy

Question 18

What are the 3 exercise associated myopathies?

Answer 18

Exertional rhabdomyolysis
Polysaccharide storage myopathy

Question 19

What are the two types of exertional rhabdomyolysis?

Answer 19

Sporadic - one off, unusual occurrence
Recurrent episodes - from underlying conditions

Question 20

What muscles does sporadic exertional rhabdomyolysis effect?

Answer 20

Hindlimb muscles

Question 21

What are the clinical signs of sporadic exertional rhabdomyolysis?

Answer 21

Stiff gait
Refuse to move
Hard, painful muscles
Distress - like a cramp

Question 22

What is the cause of sporadic exertional rhabdomyolysis?

Answer 22

Overtraining
After a rest period without reducing food
Dietary deficiencies - electrolytes

Question 23

How do you diagnose exertional rhabdomyolysis?

Answer 23

Measure CK and AST

Question 24

What is the treatment for exertional rhabdomyolysis?

Answer 24

Rest
NSAIDs
IV fluids if severe

Question 25

How do you prevent sporadic exertional rhabdomyolysis?

Answer 25

Regular exercise Warm up/cool down Dont overexert Reduce feed when exercise drops Electrolyte/vitamin supplement

Question 26

What type of horse is recurrent exertional rhabdomyolysis seen in?

Answer 26

Thoroughbreds - usually very fit fillies

Question 27

What is usually the cause of recurrent exertional rhabdomyolysis?

Answer 27

An abnormality in calcium regulation

Question 28

How do you prevent recurrent exertional rhabdomyolysis?

Answer 28

Feed a high fat low starch diet Exercise daily Dantrolene - muscle relaxant

Question 29

What is polysaccharide storage myopathy (PSSM)?

Answer 29

A glycogen storage disorder so glycogen and abnormal polysaccharides build up in muscle type 2 fibres

Question 30

What type of horse is polysaccharide storage myopathy (PSSM) seen in?

Answer 30

Draught horses Quarter horses Warm bloods NOT pure thoroughbreds

Question 31

What are the two different types of polysaccharide storage myopathy (PSSM)?

Answer 31

Type 1 - mutation in glycogen synthase enzyme Type 2 - no mutation

Question 32

What type of horses is type 1 polysaccharide storage myopathy (PSSM) seen in?

Answer 32

European draught horses Uncommon in British ones

Question 33

What are the clinical signs of polysaccharide storage myopathy (PSSM)?

Answer 33

Acute episodes of tying up Gait abnormalities Painful hindquarter muscles - more difficult to ride Difficulty lifting limbs

Question 34

How do you treat polysaccharide storage myopathy (PSSM)?

Answer 34

Rest and NSAIDs for acute episodes High fat low starch diet

Question 35

What can you feed horses on a high fat low starch diet?

Answer 35

Just add vegetable oil - unpalatable, can go rancid, large amounts Commercially prepared high fat balanced feeds

Question 36

What can cause an atypical myopathy?

Answer 36

Hypogycin A toxin in helicopter seeds/leaves from sycamore tree

Question 37

What is an atypical myopathy?

Answer 37

When a horse is found recumbent/sudden death in the field Not associated with exercise

Question 38

When do atypical myopathies happen more?

Answer 38

In autumn - falling seeds/leaves

Question 39

What are the clinical signs of atypical myopathy?

Answer 39

Sudden onset muscle weakness/stiffness Recumbency Normal appetite Respiratory difficulty Choke - weak neck muscles Death

Question 40

What is the treatment for atypical myopathy?

Answer 40

Intensive care, nursing IV fluids Regular turning Analgesic

Question 41

How do you prevent atypical myopathy?

Answer 41

Avoid affected fields or fence off around trees

Question 42

What blood tube do you use for testing for CK?

Answer 42

Green - heparin anticoagulant Red - plain tube