PathophysiologyMuscle disorders Flashcards
what is tying up disease also known as
rhabdomyolysis
name a acquired exertional muscle disease
tying up disease - rhabdomyolysis
what is the most common muscular disorder in horses
Rhabdomyolysis
List 7 clinical signs of rhabdomyolysis
stiff, stilted gait
excessive sweating
increased resp rate after exercise
firm painful muscles
reluctant to move forward
occasional dark urine
why do horses with rhabdomyolysis get dark urine
breakdown of myoglobin
List 3 things that can cause rhabdomyolysis
overexertion
dietary imbalances
exhaustion
describe how overexertion leads to rhabdomyolysis
increase in work intensity without a strong musculoskeletal foundation
Z-disk instability—> overstretching of myofibers—> sarcolemma stretching
Describe how dietary imbalances can lead to rhabdomyolysis
Electrolytes (Na and Ca) both important in neural transmission and muscle contraction
Low Vitamin E intake: Poor antioxidant state
Describe how exhaustion can lead to rhabdomyolysis
TB and endurance horses training in hot, humid weather : electrolytes loss in sweat and dehydration
why does recurrent exertional rhabdomyolysis occur
Intermittent form of rhabdomyolysis in horses likely linked to abnormal calcium regulation in myofibers
List 4 risk factors of recurrent exertional rhabdomyolysis
fit horses with nervous temperament
Young mares more at risk, but no associated with oestrus cycle
Lack of turnout
Held back during gallop
what is PSSM-1
polysaccharide storage myopathy
genetic mutation means that glycogen synthase enzyme is constantly turned on -unable to adequately breakdown glycogen as it is stored wrong
which horses is PSSM-1 seen
most seen in continental European draft brees
very rare in light breeds- unlikely in TB
List the possible risk factors of PSSM-1
Breed
exercise of more than 20min in one session
what is the difference between PSSM-1 and PSSM-2
PSSM-1 - genetic
PSSM-2- unknown cause- Myofibrillar myopathy: oxidative deficit????
Descrieb how PSSM-1 presents
most draft horses aymptomatic
stiffness after a short period of exercise –> reluctance to move forward, poor performance, sweating (most severe sign= myoglobinuria)
what is the mean age for diagnosis of PSSM-1
4-8 years
what is myofibrillar myopathy
a type of PSSM-2 that has an abnormal desmin protein and there fore the muscles don’t contract normally
List 6 plants that can cause non-exertional muscle damage
sycamore
cassia spp
box elder
Malva parviflora
eppatorium spp
Haplopparpus spp
What is equine atypical myopathy
toxic rhabdomyolysis associated with Hypoglycin A ingestion(sycamore seeds)
What are the clinical signs of equine atypical myopathy
stiffness
muscle fasciculations
weakness
sweating
myoglobinuria
colic
reduced/ absent GI sounds
what is the prognosis of equine atypical myopathy
Bad - high mortality rates (68%)
what is immune-mediated muscle damage normally associated with
previous resp infection
Describe how we can confirm sporadic rhabdomyolysis
clinical signs and elevated muscle enzymes
what type of muscle disease is PSSM
exertional - genetic
List 2 breeds that get HYPP (hyperkalemic periodic paralysis)
quarter horses and QH derived breeds
Describe how HYPP occurs
sodium channels leak and cause prolonged depolarisation and abnormal action potentials
small increases in potassium cause depolarisations
List the clinical signs of HYPP
sporadic attacks of stiffness
muscle tremors
weakness and collapse
breathing difficulties
prolapsed third eyelids
what contains Hypoglycin A that horses might eat
sycamore seeds
Describe how does hypoglycin A cause disease
hypoglycin A gets metabolised in the liver and in muscles, it then acts in the myofibres to stop fatty acid oxidation
what bacteria commonly cause myonecrosis
clostridium perfringes
clostridium septicum sometimes
what usually is the inciting cause of myonecrosis
IM injections (usually biological products) or puncture wounds
how soon after injections does myonecrosis occur
6-72 hours
List the clinical signs of myonecrosis
fever
stiffness
severe pain
gangrene
crepitation
Describe how do we treat myonecrosis
remove all necrotic tissue and allow secondary intention healing
antibiotics - high dose penicillin or metronidazole
analgesia - flunixin or phenylbutazone
