Veterinary Pathology of Muscular System

1. Veterinary Pathology of
Muscular System

2. General Reaction of the
Muscles
• Rigor mortis—After death Muscles
stiffening
• Atrophy
• Hypertrophy

3. Atrophy
• Denervation atrophy
• Disuse atrophy
• Atrophy of Cachexia

4. Hypertrophy
• Excessive use
• Compensatory

5. Congenital and Inherited
Defects
1. Hyperplasia of muscle fibers
2. Muscular dystrophy
3. Myotonic syndrome
4. Metabolic myopathies
5. Myasthenia gravis

6. 1. Hyperplasia
• Congenital and hereditary in lambs and
calves

7. 2. Muscular Dystrophy
• True Muscular Dystrophy of
humans, dogs, cats, and some
other animals-X-linked
recessive disorder in gene
coding for dystrophin, a
sarcolemmal associated
cytoskeletal protein
– Brown Swiss weaver
syndrome
– Marino sheep
– Hereditary muscular dystrophy
of Labradors
• Secondary – mostly
degenerative – secondary to
nutritional deficiencies

8. • Apart from
emaciation, normal
muscles replaced
by adipose tissue
and fibrous tissue

9. 3. Myotonic Syndrome
• Occurring as episodes
• Ion Channel defects -
dimpling
• Inherited or acquired
– Hereditary myotonia –
electromyograph – dystrophy
– Marino sheep, Angora
goats, Chow Chow dogs,
horses
– Acquired myotonia –
prolonged use of
corticosteroids – dogs, cats,
humans
– Hypercortisolism
Defined clinically as a temporary inability of skeletal muscle fibers to relax

10. Periodic paralysis
• Group of inherited muscle disorders
• In humans, hypokalemic, normokalemic,
and hyperkalemic periodic paralysis
• Electric myotonia and pseudomyotonia is
a feature of many of the periodic paralyses
(paramyotonias)

11. Hperkalemic periodic paralysis
in horses
• Inherited as autosomal dominant trait
• Respiratory noise due to laryngospasm –
dysphagia – emaciation
– Initial signs include muscle fasciculation,
flashing of the third eyelid, muscle spasm,
and respiratory stridor.
– In sever attacks – collapse – recumbency
associated with hypotonia.

12. 4. Metabolic Myopathies
• Glycogen storage disease in cattle and
dogs
• Other storage diseases – nervous signs

13. 5. Myasthenia gravis
• Congenital -
Acetylcholine
receptors are few in
number – puppies –
autosomal recessive
trait
• End plate receptors
are blocked by
anticholinesterase
receptor antibodies -
thymoma

14. Circulatory Diseases of Muscles
• Each muscle fiber supplied by 3-12
capillaries – Type I fibers more capillaries
• Transient ischemia of few hrs duration _
coagulation of contractile proteins
recovery within 20 days
• 6-12 hrs – necrosis – replaced by fibrous
and adipose tissue
• >24 hrs – fibrous tissue

15. Compartment Syndrome
• Moderately vigorous but non exhaustive
contraction in well coditioned athletes
• Infarction of Supracorticoid muscle of broilers -
Contraction – collapse of venous flow – arterial
increases – pressure – contraction –
intramuscular pressure increased to obliterate
venous and then arterial blood pressure –
accumulation of water in interstitial tissue –
ischemia – edema – pressure builds in 1-4 hrs

16. Downer Syndrome
Ischemic Muscle Necrosis
• External Pressure or weight of the body
– Prolonged anesthesis
– Muscle, joint, or bone damage
– Metabolic or neurogenic disorders
• Animals in good condition are affected mostly
• Pressure on veins – slow venous return –
edema – thrombus formation – ischemia –
necrosis – hemorrhages - hematoma

17. Muscle Crush Syndrome
• Acute accidental trauma
• Hemorrhage – pressure – ischemic
necrosis

18. Vascular Occlusive Syndrome
• Iliac artery syndrome in horses
• Pregnancy – ewes carrying twins and
triplets – ischemia of internal abdomen

19. Nutritional Myopathy
(young animals)
• Deficiency of vitamin E /
selenium - glutathionperoxidase
• Cattle and sheep are mostly
affected; horses are moderately
affected; dogs and cats have
least predisposition
• Degeneration of muscles
• Rapidly growing animals are
affected
• Skeletal muscles and
myocardium is affected Fibrosis and Mineral Deposition

20. Transport Myopathy
• Wild and domestic animals
• Lesions same as in nutritional myopathy

21. Toxic Myopathies
• Gossipol - Cumulative effect at 450ppm -
Death due to heart failure
• Monensin
• Copper, cobalt, iron, silver, cadmium, zinc,
mercury, selenium
• Sulfur

22. Exertional Myopathies
• Azoturia (paralytic myoglobinuria, Monday
morning disease)
• Tying-up
• Capture myopathy

23. Myositis
• Suppurative
• Staphylococcal Granuloma
• Gas gangrene and malignant edema
– C. septicum
– C. perfringens
– C. novyi
– C. Sordelli
• Black leg
– C. chauvoei
• Eosinophilic myositis – G. Shepherd

24. Parasitic Diseases of muscles
• Sarcosporidiosis
• Trichenellosis
• Cysticercosis
• Toxoplasmosis