Muscle Flashcards
Enzyme activities to assess muscle damage
Creatine kinase (CK) Aspartate aminotransferase (AST) Lactate dehydrogenase (LDH)
What is Serum CK a sensitive indicator for?
myonecrosis in both skeletal and heart muscle
When does Serum CK activity increase?
Increased within hours of a muscle insult and peaks within 4-6 hours after injury
When can CK elevate?
training
transport
strenuous exercise
What enzyme has high activity in skeletal and cardiac muscle as well as Liver, RBCs, and other tissues?
AST
When is the peak time for AST levels after an insult?
24 hours
What do elevations in CK and AST reflect?
recent or active myonecrosis
What do elevations of CK reflect?
myonecrosis is likely going on
What do elevated AST and decreasing or normal CK levels indicate?
Myonecrosis not continuing
Elevations in LDH specify what?
rhabdomyolysis
myocardial necrosis
hepatic necrosis
What tests assess concurrent renal disease?
Urine specific gravity White blood cell count Protein content Red Blood cell count Evaluation of cast formation
What does a positive Hemastix test in the absence of hemolysis or RBCs in urine indicate?
Myoglobinuria
Exercise Challenge test
15 mins of slow trot with CK activity sampled before and 4-6 hours after
What do elevations of greater than 5-fold CK indicate?
exertional rhabdomyolysis
Electomyography
to detect spontaneous or evoked potentials of neurogenic or myogenic
What do horses with abnormalities show on electromyography?
Spontaneous electrical activity
Fibrillation potentials: spontaneous firing of muscle fibers
Positive sharp waves
Myotonic discharges: bursts of complex high-frequency potentials
Complex repetitive discharges
What are EMG and NCVs used to classify?
classify the disease Neuropathic or Myopathic
Use of Nuclear Scintigraphy
ID some forms of muscle damage
area of deep muscle damage
How does Nuclear Scintigraphy work?
Technetium 99 m methylene diphosphonate is taken up in inflamed and damaged muscle
How is muscle fiber disruption seen on Ultrasonography?
hypoechoic area with loss of the normal fiber striation
How do es a defect in muscle/hematoma appear on ultrasonography?
Hypoechoic
How does increased connective tissue or loss of muscle appear on ultrasonography?
Hypoechoic
How does mineralization or gas pockets appear on ultrasonography?
Hyperechoic shadowing artifacts
“Sweeney”
suprascapular nerve is damaged and muscle over the scapula are atrophied
How long does it take for denervation to result in 50% muscle mass loss?
2 - 3 week period
What are the causes of Atrophy?
Denervation
Disuse
Malnutrition and cachexia
Immune-mediated myositis
HYPP
Hyperkalemic Periodic Paralysis
What causes HYPP?
inherited defect in the skeletal muscle sodium channel
What type of trait is HYPP?
Autosomal dominant
What does HYPP cause?
Abnormal skeletal muscle membrane excitability leads to episodes of myotonia, muscle contraction, and paralysis
What can trigger an episode of HYPP?
Ingestion of diets high in potassium, alfalfa hay, molasses
Electrolyte supplements
Sudden dietary changes and fasting
Anesthesia, heavy sedation or trailer rides
What are the clinical signs of an episode of HYPP?
Myotonia
prolapse of the third eyelid
Sweating
muscle fasciculations in the flanks, neck, and shoulders and then become generalized
Respiratory distress due to paralysis of the upper respiratory muscles
dysphagia
What are the clinical pathological signs seen in horses with HYPP?
Hyperkalemia
Hemoconcentration
Mild hyponatremia
How do you control HYPP?
Decreasing dietary potassium and increasing renal losses of potassium
Avoid high potassium feeds
Regular exercise
Balanced minerals
Commercially available complete feeds with a guaranteed Potassium content
What drugs are used to control horses with HYPP?
Acetazolamide
Acetazolamide
stabilizes blood glucose and potassium by stimulating insulin secretion
Muscle Cramping
painful condition that arises from hyperactivity of motor units cause by repetitive firing of the peripheral and/or central nervous system
What is the cause of Muscle cramping?
Dehydration
Electrolyte abnormalities
Disturbances in thermoregulatory and local circulatory function
What deficiency is common in horses?
Sodium
What deficiencies can result in muscle stiffness, weakness, and occasional elevation in CK?
sodium or potassium
What is a common muscle condition seen in endurance horses?
Muscle cramping
What are the common electrolyte abnormalities of exhaustion?
hypochloremic metabolic alkalosis with hypokalemia, hypomagnesemia and low serum ionized calcium
What can be seen with muscle cramping in horses?
Synchronous diaphragmatic flutter
What is the treatment for muscle cramping?
Signs abate with rest or light exercise
oral or intravenous polyionic fluids
Cooling horses down with water and fans
Supplement with sodium chloride and potassium chloride
What are the two types of Rhabdomyolysis?
Non-exertional
exertional
Clostridial Myonecrosis
Disease characterized by a rapid clinical sourse, fever, systemic toxemia, and high mortality
Clinical signs of Clostridial Myonecrosis
Crepitus Malodorous serosanguinous fluid Tremors Ataxia Dyspnea recumbence coma death within 12-24 hours
What is the cause of Clostridial Myonecrosis?
Recent injection
What is a site of invasion for Clostridium in foals?
Umbilicus
What is the treatment for Clostridial myonecrosis?
Antibiotic therapy
Aggressive surgical debridement
supportive care
What is the drug of choice for treatment for Clostridial myonecrosis?
Penicillin
Clinical signs of Rhabdomyolysis associated with Streptococcus
Stiff gait
rapidly to markedly firm, swollen painful epaxial and gluteal muscles
What are the two causes of Rhabdomyolysis/ Streptococcus equi?
- Toxic Shock
2. Bacteremia
What is the treatment for Rhabdomyolysis/ Streptococcus equi?
Flushing infected guttural pouches and draining abscessed lymph nodes
NSAIDs
CRI of lidocaine, detomidine, or ketamine
What are the clinical signs of Immune-mediated polymyositis?
Rapid onset of muscle atrophy of the back and croup muscles
accompanied with stiffness
Generalized weakness
What do you see on biopsy of Immune mediated Polymyositis?
lymphocyte vasculitis
angular atrophy
fiber necrosis with macrophage infiltration
regeneration
What is the treatment for Immune Mediated Polymyositis?
Corticosteroids
What viruses are associated with myopathy?
Equine Influenza A2
EHV1
What muscles are affected by virus associated myopathy?
Skeletal muscles and cardiac muscles
Seasonal Pasture Myopathy and Atypical Myopathy
a highly fatal acquired lipid storage myopathy of pastured horses kept on wooded pastures for more than 12 hours a day without additional feed
What are the clinical signs of Seasonal Pasture Myopathy and Atypical Myopathy?
Acute muscular weakness Sweating fasciculations stiffness tachycardia tachypnea recumbence myoglobinuria
What are the clinical pathological signs of Seasonal Pasture Myopathy and Atypical Myopathy?
increase in CK and AST activity
hyperglycemia
lactic acidemia
How do you diagnose Seasonal Pasture Myopathy and Atypical Myopathy?
Identified deficiency in multiple acetyl coA dehydrogenase
Isolation of the conjugated toxic metabolite methylenecyclopropyl acetic acid in blood or urine
Extensive necrosis in deep postural, respiratory muscles and myocardium
What is responsible for causing Seasonal Pasture Myopathy and Atypical Myopathy
Seeds of Acer species trees such as the box elder containing toxic amino acid hypoglycin A
What is the paathophysiology of the Seed of Acer species tree?
Hypoglycin A is metabolized in the liver to MCPA
MCPA irreversibly binds to multiple enzymes that are essential for metabolism fatty acids and branched chain amino acids
Accumulation of fat esters can damage muscle cell membranes, and an energy deficiency also arises from an inability to metabolize fat
What is the treatment and control of Seasonal Pasture Myopathy and Atypical Myopathy
Early aggressive supportive care
Avoid pasture with Acer species trees
What are the two forms of Postanesthetic Myoneuropathy
Localized myopathy-neuropathy
Generalized myopathy
Localized myopathy-neuropathy
occurs in muscles that are in contact with a hard surface or with compromised arterial blood supply
What is the cause of Postanesthetic Myoneuropathy?
Duration of anesthesia, ischemia, and hypoperfusion as a result of prolonged immobility, muscle compression, systemic hypotension, and hypoxia
What is the treatment for Localized myopathy-neuropathy?
Supportive care
Anti-inflammatory drugs
How do you control localized myopathy-neuropathy?
Goo padding and proper placement of limbs and body to reduce pressure
Maintaining anesthesia at the lightest plane possible and adequate arterial blood pressure
What are the clinical signs of Generalized Anesthetic Reactions?
Anxiety hyperthermia tachycardia tachypnea profuse sweating myoglobinuria
What are the aims of treatment for myopathy-neuropathy?
Relief of pain
Correction of fluid and electrolyte abnormalities
Attempts to prevent ongoing necrosis
High-quality nursing care
What is used to release calcium from the sarcoplasmic reticulum helping to break the cycle of muscle damage from myopathy-neuropathy?
Dantrolene
What myopathy is common in jumpers, dressage, harness horses and thoroughbreds?
Exertional myopathies of the lumbar and gluteal muscles
What myopathy is common in Quarter horses?
Strain semitendinosus and semimembranosus muscles
What is caused by chronic exertional myopathies?
fibrotic myopathy
What is a clinical sign of strain the semitendinosus and semimembranosus muscles?
Stride has a short anterior phase with a characteristic hoof-slapping gait
No pain
How do you treat strain of semitendinosus and semimembranosus muscles?
Surgical procedures fro correction of fibrotic myopathy
excision or transection of the fibrotic part of the muscle
What is the most common muscle disorder of horses?
Sporadic Exertional Rhabdomyolysis
What are the clinical signs of Sporadic Exertional Rhabdomyolysis?
Stiff gait
excessive sweating
high respiratory rate during or after exercise with firm painful muscles after 15-30 minutes of light exercise
Myoglobinuria
How do you diagnose Sporadic Exertional Rhabdomyolysis?
abnormally elevated serum CK and AST
Myoglobinuria
What causes Sporadic Exertional Rhabdomyolysis?
Level of exercise
Signs of muscle stiffness and gait changes
Severity of elevations of serum CK activity
What dietary imbalance exacerbates Sporadic Exertional Rhabdomyolysis?
selenium and vitamin E
How do you treat Sporadic Exertional Rhabdomyolysis?
Anti-inflammatories Sedative or tranquilizer Fluid therapy Muscle relaxants Nutrition
What can severe rhabdomyolysis lead to?
Renal damage due to combined nephrotoxic effects of myoglobinuria, dehydration, and NSAIDs
How do you treat Sporadic Exertional Rhabdomyolysis?
Stall rest
Resume training gradually
Avoid excessive calorie intake and ensure proper nutritional balance
What triggers Recurrent Exertional Rhabdomyolysis?
Exercise
What are the clinical pathological findings of Recurrent Exertional Rhabdomyolysis??
Rise in serum CK and myoglobin
Rise in Cortisol concentrations
How do you diagnose Recurrent Exertional Rhabdomyolysis?
Biopsy
What type of diet should horses be on to manage Recurrent Exertional Rhabdomyolysis?
Low-starch High-fat concentrates
What is discouraged for horses with Recurrent Exertional Rhabdomyolysis predisporsition?
Days off training in a stall
What medications are used to help control Recurrent Exertional Rhabdomyolysis?
Acepromazine Reserpine fluphenazine Dantrium sodium Oral Dantrolene Phenytoin
Polysaccharide Storage Myopathy
horses have 2-fold higher glycogen concentration than normal horses and abnormal granular amylase-resistant inclusion in histiologic sections because of a malfunction in glycogen synthase enzyme due to a single base-pair mutation in GYS1
What is the common trigger for Type 1 Polysaccharide Storage Myopathy?
Exercise
How do you diagnose Type 1 Polysaccharide Storage Myopathy?
Elevated serum CK and AST
Exercise test produce a minimum of a three fold elevation in CK activity 4-6 hours after exercise
Muscle Biopsy
