Test 2 - Muscle Diseases Flashcards
_______ has remarkable sensitivity as indicator of myonecrosis in skeletal and heart muscle.
Increases within hours of a muscle insult and peaks within 4-6 hrs after injury.
Creatinine Kinase has remarkable sensitivity as indicator of myonecrosis in skeletal and heart muscle.
Increases within hours of a muscle insult and peaks within 4-6 hrs after injury.
TRUE/FALSE
Creatinine Kinase is a great marker at all times.
FALSE
- Limited evaluation accompanying training, transport, strenuous exercise.
- Recumbent or colicky animals may also have slightly elevated CK activity
- Rhabdomyolysis usually results in substantial elevations in the activity of enzyme (1000-100,000)
TRUE/FALSE
Elevations in Aspartate Aminotransferase are not specific for myonecrosis.
TRUE
AST also has high activity in skeletal & cardiac muscle (also liver, RBCs, & other tissues).
What tissues does AST have high activity in?
high activity in skeletal & cardiac muscle (also liver, RBCs, & other tissues).
Elevations may result from hemolysis, muscle, liver, or other organ damage.
Describe the relationship of CK and AST in regards to myonecrosis.
Describe the peak hours and half life.
• AST activity rises more slowly in response to myonecrosis than does CK.
• Peaking 24 hours after the insult and the T1/2 life of AST is much longer than CK
• Comparing Serial Activities:
• Elevations in CK & AST reflect relatively recent or active myonecrosis
• CK remains persistently elevated, myonecrosis is likely ongoing
• Elevated AST activities accompanied by decreasing or normal CK activities indicate that myonecrosis is not continuing.
When can elevations in Lactate Dehydrogenase be seen?
Elevations are not specific to skeletal muscle. May occur with rhabdomyolysis,
myocardial necrosis, and/or hepatic necrosis. RBCs lysis can also liberate AST and LDH.
What is the importance of a U/A when assessing muscle disease?
U/A is particularly important with myoglobin, elevations in creatinine or persistent electrolyte imbalances.
A positive Hemastix test (ortho-toluidine) in the absence of hemolysis or RBCs in urine is highly suggestive of ____________.
A positive Hemastix test (ortho-toluidine) in the absence of hemolysis or RBCs in urine is highly suggestive of myoglobinuria
What is the purpose of the exercise challenge test?
To investigate disease processes that are precipitated by exercise, not currently showing CS
Describe the Exercise challenge test.
- Goal is to induce subclinical elevations in serum CK activity → ↑ CK is more likely to occur if slow trotting is performed rather than strenuous exercise.
- 15 minutes @ constant slow trot → if any signs of muscle tone changes develop, exercise should be concluded
- Should be taken before and 4-6 hrs after exercise → CK-blood samples taken immediately after exercise do not reflect the amount of exercise induced muscle damage.
- In healthy horses 15-30 minutes of light exercise → rarely causes >3x ↑ in CK activity
CK elevations greater than _______ from the exercise challenge test are indicative of exertional rhabdomyolysis.
CK elevations greater than 5x from the exercise challenge test are indicative of exertional rhabdomyolysis.
When using nuclear scintigraphy in the diagnosis of muscle disease, _______is taken up by inflamed & damaged muscle.
When using nuclear scintigraphy in the diagnosis of muscle disease, Technetium 99M methylene diphosphonate (MDP) is taken up by inflamed & damaged muscle.
Describe the following muscle abnormalities as appearing hyper or hypoechoic on U/S:
• Acute injury: muscle fiber disruption is seen as relatively _______ areas with loss of
the NL fiber striation
• Torn muscle: ________ margin. Tears in muscle fascia may be identified
• Defect in muscle/hematoma is _______. progressively more echogenic as the
muscle repairs
• ↑ CT or loss of muscle cell mass shows ________
• Mineralization or gas pockets shows ______ shadowing artifacts
• Acute injury: muscle fiber disruption is seen as relatively hypo echoic areas with loss of
the NL fiber striation
• Torn muscle: Hyperechoic margin. Tears in muscle fascia may be identified
• Defect in muscle/hematoma is hypoechoic. progressively more echogenic as the
muscle repairs
• ↑ CT or loss of muscle cell mass shows hyperechoic
• Mineralization or gas pockets shows hyper echoic shadowing artifacts
TRUE/FALSE:
Fixation in formalin is acceptable for all muscle disorders
FALSE
Formalin fixation results in artifacts, which can impact proper interpretation of pathology. May want to send it in saline.
Describe the procedure for muscle biopsy.
- Enough muscle should be obtained to form square inch sample (minimum)
- Samples don’t tolerate shipping well
- Care must be exercise to infiltrate only the SQ tissues with anesthetic agent
- 2 parallel incisions inch apart should be made longitudinal to muscle fibers w/ scalpel
- Muscle should only be handled in one corner using forceps & avoid crushing
- Routine histopath samples can be placed in formalin
Caffein and Halothane are used to diagnoes ________.
Caffein and Halothane are used to diagnose Recurrent Exertional Rhabdomyolysis & susceptibility to Malignant Hyperthermia.
________ is caused by inherited defect in skeletal muscle sodium channel.
Hyperkalemic Periodic Paralysis
What horse breeds are affected by Hyperkalemic Periodic Paralysis?
Quarter Horses,
American Paint Horses, Appaloosas & Quarter Horse Cross bred animals worldwide
TRUE/FALSE
Foals born in 2007 and later testing heterozygus affected for HYPP (H/h) are not eligible for registration with the AQHA.
FALSE.
They must be homozygous (H/H)
ingestion of diets high in _________, alfalfa hay, molasses can trigger epidose of HYPP.
What are some other causes.
Potassium
Stress can precipitate CS → the onset of signs is often unpredictable without a definable cause
• Other possible precipitating factors:
• Cold weather
• Pregnancy or concurrent disease
• Rest following exercise
TRUE/FALSE
Serum CK shows no change or only modest ↑ during episodic fasciculations and weakness of HYPP
TRUE
What are some respiratory tract abrnomalities that may be seen with HYPP?
- Respiratory distress due paralysis of the upper respiratory muscles
- Dysphagia
- Pharyngeal collapse & Edema
- DDSP
- Laryngeal paralysis
What are the relevant clinical pathological findings of HYPP?
- Hyperkalemia (6-9 mEq/L)
- Hemoconcentration
- Mild hyponatremia during clinical manifestations of the disease with normal acid-base balance
- Potassium concentration returns to normal following the abatement of CS
- Some horses may have normal serum potassium concentrations during minor episodes of muscle fasciculations
How is HYPP Diagnosed?
Demonstration of the base-pair sequence substitution in the abnormal segment of the DNA
encoding for the alpha subunit of the sodium channel - muscle biopsy
• Mane or tail hair should be sent to a licensed laboratory
How is HYPP Controlled?
List Diet, exercise and medical control.
• ↓ dietary potassium and ↑ renal losses of potassium are the 1° tests
• Avoid high potassium feeds such as alfalfa, soybean meal, sugar molasses, beet molasses
• High water content of pasture grass contains lesser amounts of K+
• Regular exercise and/or frequent access to a large paddock also beneficial
• Diets higher in K+ should gradually be adjusted over a period of 2 weeks.
• Vit E, selenium, salt and balanced minerals
• Commercially available complete feeds with guaranteed K+ content
• For horses with recurrent episodes
• Acetazolamide (2-3 mg/kg orally, every 8-12 hrs) → stabilizes blood glucose & K+ by stimulating insulin secretion
• Hydrochlorothiazide (0.5 - 1 mg/kg orally q12 hrs)
• Effects are different mechanisms - both ↑ renal K+ excretion
• Meds may be restricted in competitions
What is the prognosis for horses with HYPP?
- In most HYPP is a manageable disorder → recurrent bouts may occur and several can be fatal
- Owners should be strongly discouraged from breeding these animals → dominant trait, breeding an affected horse to a normal horse results in a 50% chance of producing a foal with HYPP
- Owners of affected horses should advise vets of HYPP status → before anesthesia or procedures during heavy sedation.
_______ is a painful condition that arises from hyperactivity of motor units. it is Caused by repetitive firing of the peripheral and/or CNS. The origin in most cases is intramuscular portion of the motor nerve terminals.
Muscle Cramping
Muscle cramping may result from diets that are deficient in Na or K. Because of this, ______ may also be seen with it.
Muscle cramping may result from diets that are deficient in Na or K. Because of this, Synchronous diaphragmatic flutter (thumps) may also be seen with it.
