Lame - Equine muscle disorders Flashcards
What can you assess on clinical exam for equine muscle disorders?
Degree and symmetry
Firmness
What causes rapid muscle atrophy?
Neurogenic atrophy
What does a base narrow stance indicate?
Weakness - elephant on a tub
What are the main two muscle enzymes?
Creatine kinase
AST
What is the kinetic for CK?
Peaks at 4-6 hours
Rises higher but reduces quicker
What is the kinetics for AST?
Peaks at 24 hours, but takes a couple of weeks to return to normal
What does it mean if both CK and AST are high?
Muscle damage - happened over 24 hours ago
What does it mean if CK is high but AST is normal?
Acute muscle damage
What does it mean if CK is normal but AST is very high?
Two weeks after known case of muscle damage
What does it mean if CK is normal and AST is slightly elevated?
Red herring - AST is not muscle wastage specific, can mean liver damage too
What can cause dark coloured urine in horses?
Myoglobinuria
Why would there by myoglobin in the urine?
From break down of muscle cells
What can myoglobinuria cause?
Nephrotoxic - acute renal failure
When is myoglobinuria seen?
Typically only in severe rhabdomyolysis cases
Where do you do a muscle biopsy in horses?
Semimembranosus
Tail head for equine motor neurone disease
What method do you use for an equine muscle biopsy? What needle?
Bergstrom needle
Open method
What are the big two myopathies?
Exercise associated myopathies
Atypical myopathy
What are the 3 exercise associated myopathies?
Exertional rhabdomyolysis
Polysaccharide storage myopathy
What are the two types of exertional rhabdomyolysis?
Sporadic - one off, unusual occurrence
Recurrent episodes - from underlying conditions
What muscles does sporadic exertional rhabdomyolysis effect?
Hindlimb muscles
What are the clinical signs of sporadic exertional rhabdomyolysis?
Stiff gait
Refuse to move
Hard, painful muscles
Distress - like a cramp
What is the cause of sporadic exertional rhabdomyolysis?
Overtraining
After a rest period without reducing food
Dietary deficiencies - electrolytes
How do you diagnose exertional rhabdomyolysis?
Measure CK and AST
What is the treatment for exertional rhabdomyolysis?
Rest
NSAIDs
IV fluids if severe
How do you prevent sporadic exertional rhabdomyolysis?
Regular exercise
Warm up/cool down
Dont overexert
Reduce feed when exercise drops
Electrolyte/vitamin supplement
What type of horse is recurrent exertional rhabdomyolysis seen in?
Thoroughbreds - usually very fit fillies
What is usually the cause of recurrent exertional rhabdomyolysis?
An abnormality in calcium regulation
How do you prevent recurrent exertional rhabdomyolysis?
Feed a high fat low starch diet
Exercise daily
Dantrolene - muscle relaxant
What is polysaccharide storage myopathy (PSSM)?
A glycogen storage disorder so glycogen and abnormal polysaccharides build up in muscle type 2 fibres
What type of horse is polysaccharide storage myopathy (PSSM) seen in?
Draught horses
Quarter horses
Warm bloods
NOT pure thoroughbreds
What are the two different types of polysaccharide storage myopathy (PSSM)?
Type 1 - mutation in glycogen synthase enzyme
Type 2 - no mutation
What type of horses is type 1 polysaccharide storage myopathy (PSSM) seen in?
European draught horses
Uncommon in British ones
What are the clinical signs of polysaccharide storage myopathy (PSSM)?
Acute episodes of tying up
Gait abnormalities
Painful hindquarter muscles - more difficult to ride
Difficulty lifting limbs
How do you treat polysaccharide storage myopathy (PSSM)?
Rest and NSAIDs for acute episodes
High fat low starch diet
What can you feed horses on a high fat low starch diet?
Just add vegetable oil - unpalatable, can go rancid, large amounts
Commercially prepared high fat balanced feeds
What can cause an atypical myopathy?
Hypogycin A toxin in helicopter seeds/leaves from sycamore tree
What is an atypical myopathy?
When a horse is found recumbent/sudden death in the field
Not associated with exercise
When do atypical myopathies happen more?
In autumn - falling seeds/leaves
What are the clinical signs of atypical myopathy?
Sudden onset muscle weakness/stiffness
Recumbency
Normal appetite
Respiratory difficulty
Choke - weak neck muscles
Death
What is the treatment for atypical myopathy?
Intensive care, nursing
IV fluids
Regular turning
Analgesic
How do you prevent atypical myopathy?
Avoid affected fields or fence off around trees
What blood tube do you use for testing for CK?
Green - heparin anticoagulant
Red - plain tube
