E2: Muscle Diseases Flashcards
Serum CK offers remarkable sensitivity as aan indicator of __________.
Myonecrosis (of heart and skeletal muscle)
What is the expected CK range for a horse that has just begun training or in response to moderate exercise?
400-500 IU/L
Which enzyme, CK or AST, rises more slowly in response to myonecrosis?
AST
What does it indicate if AST is increased in conjunction with decreasing or normal CK activity? What is CK remains elevated?
Myonecrosis has occured but is not continuing
CK remaining elevated = ongoing myonecrosis
What does a poitive Hemastic test n the absence of hemolysis or RBCs in urine suggest?
Myoglobinuria
In the exercise challenge test, a horse should be kept at a constant slow trot for ____ minutes. When must you take the sample?
15 minutes
4-6 hours after exercise (not immediately!)
What is a normal result for a healthy host post- Exercise challenge test? What result indicates exertional rhabdomyolysis?
Normal: Rarely >3x CK
Abnormal: >5x CK
What will a electromyography of a healthy horse show? What about a horse with muscle abnormalities?
Normal: little to no spontaneous electrical activity until muscles contract
Abnormal: spontaneous electrical activity
Electromyography (EMG) and __________ are used to classigy the disease Neuropathic or Myopathic.
Nerve conduction velocity (NCV)
What element isused in nuclear scintigraphy to ID some forms of muscle damage?
Technetium 99m methylene diphosphonate (MDP)
On US, does muscle fiber disruption appear hyper- or hypoechoic? How does increased connective tissue or loss of muscle cell mass look?
Hypoechoic
Hyperechoic
Responses to ____ and ______ are used to diagnose recurrent exertional rhabdomyolysis and susceptibility to malignant hypethermia.
Caffeine
Halothane
Complete denervation of a muscle results in a >50% loss of muscle mass within ______ weeks.
2-3
What nerve is damaged in a horse with Sweeney?
Suprascapular
T/F: A QH sire who is heterozygous for HYPP who is bred with a mare who is lacking the trait has a 1/4 chance of having offspring with HYPP.
True
It is autosomal dominant genetic disorder
(QHs, American Paint, Appaloosas, and QH crossbreeds)
At what age do clinical signs usually begin in a horse with HYPP?
2-3 yrs
Why can alfalfa hay, soybean meal, and molasses trigger HYPP?
High in potassium
T/F: During a HYPP episode, CK will be greatly elevated.
False
CK shows no change or only modest increase during episodic fasciulations and weakness.
In a horse with HYPP, where does sweating and muscle fascilation commonly occur?
Flanks
Neck
Shoulders
How do you control HYPP longterm? How do you treat a horse wtih recurrent episodes?
Longterm: Diet
Acute: Acetazolamide, Hydrochlorothiazide
What type of tick infestation cause sintermittent painful muscle cramps that are not associated with exercise? Will CK levels be elevated?
Otobius megnini
Yes, CK will be elevated 4k-17k IU/L
IM injections of ______ ______ can trigger ______ myonecrosis.
Flunixin meglumine
Clostridial
How do you make a definitive diagnosis of clostridial myonecrosis? (What samples would you need and what tests would you run)
Aspirates from affected tissue - direct smear exxam + fluorescent antibody testing + anaerobic bacterial culture
The toxins from this species of clostridium are thr most potent and myonecrosis caused by this organism is fatal.
C. sordelli
What antibiotics do you use to (try to) treat clostridial myonecrosis? What else in conjunction with supportive care is indicated?
Rx: Penicillin (high dose CRI), Metronidazole PO, analgesics
Tx/Sx: Fasciotomy
What hematologic abnormalitied are associated with S. equi rhabdomyolysis?
Mature neutrophilia
Hyperfibrinogenemia
Marked increase in CK (115k-587k U/L)
Marked increase in AST (600-14.5k U/L)
What are the 2 proposed etiologies associated with S. equi rhabdomyolysis?
- Toxic shock-like reaction from profound nonspecific T cell stimulation by strep superantigens with release of +++ inflammatory cytokines
- Bacteremia w/local multiplication and exotoxinprotease production in skeletal muscle
T/F: Unrelanting pain caused by S. equi (Strangles) rhabdomyolysis necessitates euthanasia within 24-48 hours of hospitalization.
True
In what breed has immune-mediated polymyositis recently been reported?`
Quarter horses
What does IMM (immune-mediated polymyositis) cause?
Muscular atrophy (rapid onset, especially affecting back and croup muscles + stiffness)
What can you expect when you submit a muscle biopsy from a horse with IMM? Which muscles would you sample?
Lymphocyte vasculitis
Angular atrophy
Fiber necrosis w/ macrophage infiltration
Regeneration
Muscles: Epaxial and gluteals
Which viruses can cause clinical signs similar to those seen in horses with rhabdomyolysis?
Equine influenza A2
EHV-1
What is seasonal pasture myopathy? What are the clinical signs?
Highly fatal acquired lipid storage myopathy (Europe and Central-NE N. America)
CS: Acute muscle weakness, sweating, fasciculations, stiffness, tachycardia, tachypnea, recumbence, myoglobinuria
How is seasonal pasture myopathy diagnosed?
Isolation of methylenecyclopyopyl acetic acid (MCPA) in blood or urine
What tree species have speeds than contain the toxic amino acid hypoglycin A? Where is it metabolized? What type of myopathy is this toxin linked to?
Acer
Liver (to MCPA)
Atypical/Seasonal Pasture myopathy
What is the prognosis for seasonal pasture myopathy?
<75% survival rate
What are the 2 forms of post-anesthetic myoneuropathy?
- Localized
- Generalized (worse)
T/F: Generalized postanesthetic myoneuropathy is caused by compartmental syndrome.
False, cannot be the sole cause
What can you give a horse with postanesthetic myoneuropathy to help relax the muscles (in conjunction with pain meds)? How does it work?
Dantrolene sodium
Decreases release of calcium from sarcoplasmic reticulum
What is a classic feature of severe exertonal rhabdomyolysis?
Myoglobinuria
What diet imbalances can trigger and exacerbate sporadic exertional rhabdomyolysis?
High nonstructural cabs contant + low forage contant + low e-lytes
Exacerbated by inadequate selenium and vit E
What diet is recommended for a horse with recurrent exertional rhabdomyolysis?
Low-Starch, High-Fat Concentrates
Why are days off training in a stall discouraged in a horse with RER?
Post-exercise CK activity is higher following 2 days of rest compared to if performing consecutive days of the same amount of submaximal exercise
What 2-3 drugs are recommended to treat RER?
Reserpine
Fluphenazine
Dantrium sodium
What causes type 1 polysaccharide storgae myopathy and how is it diagnosed?
Genetic mutation in GYS1 gene
Muscle biopsy
What are the 2 types/etiologies of non-exertional rhabdomyolysis?
Inflammatory
Nutritional
Is clostridial myonecrosis contagious? Is it frequently fatal?
No
Yes (close to 100% mortality)
What procedure can you perform to diminish the bacterial load in a horse with Strangles?
Flush infecred guttural pouches and drain abscessed LNs
What are the treatments for immune-mediated polymyositis?
Corticosteriods (help CS and prevent progression)
What 3 conditions put horses at a high risk of developing generalized anesthetic reactions/myoneuropathy?
Malignant hyperthemria
Recurrent exertional rhabdomyolysis
Polysaccharide storage myopathy?
What are the clinical signs associated with sporadic exertional rhabdomyolysis? What is a classic feature of severe cases?
Stiff gait
Excessive sweating
High respiratory rate during or after exercise
Firm, painful muscles
Severe: Myoglobinuria (nephrotoxic) (also colic and recumbence)
What are some causes of sporadic exertional rhabdomyolysis?
Level of exercise too high
Exhaustion (hot, humid weather)
Diet imbalance (high carb diets, e-lyte imbalance, inadequate vit E/sel)
What can be included in the treatment for sporadic exertional rhabdomyolysis?
Anti-inflammatories
Sedative/tranquilizer
Fluids
Muscle relaxants (Methocarbamol)
Nutrition
Stall rest
What are some risk factors associated with RER development?
Breed- TBs
Females
Young horses
Diet (High carb in TBs)
A few days of rest before exercise
T/F: Mares appear to exhibit signs of rhabdomyolusis durng estrus, thus it may be beneficial to use progesterone inhections to suppress estrus.
True
T/F: Marbles in the uterus to mimic a pregnancy is an alternative to progesterone injections to prevent estrus-driven rhabdomyolysis.
False, don’t do that
How are the types of polysaccharide stroage myopathy determined? What do types 1 and 2 mean? Which is more aggressive?
Sensitivity to amylase digestion and GYS1 gene mutation
PSSM1= resistant + mutation = more aggressive CS
PSSM2= sensitive without mutation
How is PSSM managed?
Diet and exercise!
Low-starch, high-fat supplemented diets + regular exercise program
T/F: One common adaptation to daily training is an increase in oxidative capacity in skeletal muscle.
True
