PathophysiologyMuscle disorders

Question 1

what is tying up disease also known as

Answer 1

rhabdomyolysis

Question 2

name a acquired exertional muscle disease

Answer 2

tying up disease - rhabdomyolysis

Question 3

what is the most common muscular disorder in horses

Answer 3

Rhabdomyolysis

Question 4

List 7 clinical signs of rhabdomyolysis

Answer 4

stiff, stilted gait
excessive sweating
increased resp rate after exercise
firm painful muscles
reluctant to move forward
occasional dark urine

Question 5

why do horses with rhabdomyolysis get dark urine

Answer 5

breakdown of myoglobin

Question 6

List 3 things that can cause rhabdomyolysis

Answer 6

overexertion
dietary imbalances
exhaustion

Question 7

describe how overexertion leads to rhabdomyolysis

Answer 7

increase in work intensity without a strong musculoskeletal foundation
Z-disk instability—> overstretching of myofibers—> sarcolemma stretching

Question 8

Describe how dietary imbalances can lead to rhabdomyolysis

Answer 8

Electrolytes (Na and Ca) both important in neural transmission and muscle contraction
Low Vitamin E intake: Poor antioxidant state

Question 9

Describe how exhaustion can lead to rhabdomyolysis

Answer 9

TB and endurance horses training in hot, humid weather : electrolytes loss in sweat and dehydration

Question 10

why does recurrent exertional rhabdomyolysis occur

Answer 10

Intermittent form of rhabdomyolysis in horses likely linked to abnormal calcium regulation in myofibers

Question 11

List 4 risk factors of recurrent exertional rhabdomyolysis

Answer 11

fit horses with nervous temperament
Young mares more at risk, but no associated with oestrus cycle
Lack of turnout
Held back during gallop

Question 12

what is PSSM-1

Answer 12

polysaccharide storage myopathy
genetic mutation means that glycogen synthase enzyme is constantly turned on -unable to adequately breakdown glycogen as it is stored wrong

Question 13

which horses is PSSM-1 seen

Answer 13

most seen in continental European draft brees
very rare in light breeds- unlikely in TB

Question 14

List the possible risk factors of PSSM-1

Answer 14

Breed
exercise of more than 20min in one session

Question 15

what is the difference between PSSM-1 and PSSM-2

Answer 15

PSSM-1 - genetic
PSSM-2- unknown cause- Myofibrillar myopathy: oxidative deficit????

Question 16

Descrieb how PSSM-1 presents

Answer 16

most draft horses aymptomatic
stiffness after a short period of exercise –> reluctance to move forward, poor performance, sweating (most severe sign= myoglobinuria)

Question 17

what is the mean age for diagnosis of PSSM-1

Answer 17

4-8 years

Question 18

what is myofibrillar myopathy

Answer 18

a type of PSSM-2 that has an abnormal desmin protein and there fore the muscles don’t contract normally

Question 19

List 6 plants that can cause non-exertional muscle damage

Answer 19

sycamore
cassia spp
box elder
Malva parviflora
eppatorium spp
Haplopparpus spp

Question 20

What is equine atypical myopathy

Answer 20

toxic rhabdomyolysis associated with Hypoglycin A ingestion(sycamore seeds)

Question 21

What are the clinical signs of equine atypical myopathy

Answer 21

stiffness
muscle fasciculations
weakness
sweating
myoglobinuria
colic
reduced/ absent GI sounds

Question 22

what is the prognosis of equine atypical myopathy

Answer 22

Bad - high mortality rates (68%)

Question 23

what is immune-mediated muscle damage normally associated with

Answer 23

previous resp infection

Question 24

Describe how we can confirm sporadic rhabdomyolysis

Answer 24

clinical signs and elevated muscle enzymes

Question 25

what type of muscle disease is PSSM

Answer 25

exertional - genetic

Question 26

List 2 breeds that get HYPP (hyperkalemic periodic paralysis)

Answer 26

quarter horses and QH derived breeds

Question 27

Describe how HYPP occurs

Answer 27

sodium channels leak and cause prolonged depolarisation and abnormal action potentials

small increases in potassium cause depolarisations

Question 28

List the clinical signs of HYPP

Answer 28

sporadic attacks of stiffness
muscle tremors
weakness and collapse
breathing difficulties
prolapsed third eyelids

Question 29

what contains Hypoglycin A that horses might eat

Answer 29

sycamore seeds

Question 30

Describe how does hypoglycin A cause disease

Answer 30

hypoglycin A gets metabolised in the liver and in muscles, it then acts in the myofibres to stop fatty acid oxidation

Question 31

what bacteria commonly cause myonecrosis

Answer 31

clostridium perfringes

clostridium septicum sometimes

Question 32

what usually is the inciting cause of myonecrosis

Answer 32

IM injections (usually biological products) or puncture wounds

Question 33

how soon after injections does myonecrosis occur

Answer 33

6-72 hours

Question 34

List the clinical signs of myonecrosis

Answer 34

fever
stiffness
severe pain
gangrene
crepitation

Question 35

Describe how do we treat myonecrosis

Answer 35

remove all necrotic tissue and allow secondary intention healing

antibiotics - high dose penicillin or metronidazole

analgesia - flunixin or phenylbutazone