Equine 11-15

What are the main functions of the vertebral column?

Protect spinal cord, weight bearing, flexibility/locomotion, carry rider

What part of the vertebra protects the spinal cord?

Neural arch

What part of the vertebra is important for weight bearing?

Vertebral body

What structures provide soft tissue attachment?

Spinous and transverse processes

What regions of the horse's axial skeleton are commonly evaluated?

Head, cervical, thoracic, lumbar, lumbosacral, sacroiliac

What can problems in the cranial cervical region cause?

Ataxia and spinal cord compression

What is commonly associated with the caudal cervical region?

Osteoarthritis

What region is especially important for saddle fit?

Middle of the back

What region is important for impulsive forces during jumping?

Lumbosacral region

What can the tail tell you clinically?

Pain, stress, excitement, or discomfort

What is an important early sign of back pain?

Behavior change

Why might a horse seem "naughty" when it actually has back pain?

Pain can cause resistance or behavioral changes

What should you palpate during a back exam?

Soft tissues and spinous processes

Why is saddle fit important when evaluating back pain?

Poor fit can cause or worsen pain

What should you do in a horse with back pain regarding the limbs?

Perform a full lameness exam

What should you do in a horse with chronic lameness regarding the back?

Perform a full spinal exam

What percentage of horses with back problems had limb lameness in one cited study?

85%

What percentage of orthopedic horses with back problems were also lame?

74%

What percentage of horses with lameness also had back problems in one study?

32%

What percentage of horses with forelimb/hindlimb lameness had back pain in one study?

23%

What are major categories of vertebral disorders?

Soft tissue, osseous, neurologic

What are examples of soft tissue spinal disorders?

Sprains, strains, metabolic and infectious problems

What are examples of osseous spinal disorders?

OA, spondylosis, luxation, malformations, fractures

What can disc degeneration cause?

Segmental instability and subluxation

What is ankylosis?

Fusion of a joint

What happens to the neck with cervical joint fusion?

Reduced/stiff motion

What is capsulitis?

Inflammation of a joint capsule

What can chronic capsulitis cause?

Fibrosis and stiffness

What imaging modalities can be used for the axial skeleton?

Radiographs, ultrasound, nuclear scintigraphy

Why can axial skeleton imaging be difficult?

The region is difficult to image and findings may correlate poorly with clinical signs

What is the surgical treatment for thoracolumbar impinged spinous processes?

Spinous process resection

What is myotonia?

Delayed relaxation or prolonged contraction of skeletal muscle

What clinical signs can myotonia cause?

Muscle fasciculations and weakness

What two major inherited muscle diseases are discussed?

HYPP and GBED

What does HYPP stand for?

Hyperkalemic periodic paralysis

Is HYPP myotonic or rhabdomyolytic?

Myotonic

What type of inheritance does HYPP have?

Autosomal dominant

What ion is elevated during HYPP episodes?

Potassium

What channel mutation causes HYPP?

Voltage-dependent sodium channel

What breed is classically associated with HYPP?

Quarter Horses

Are HYPP episodes continuous?

No, horses are usually normal between episodes

What can trigger a HYPP episode?

High-potassium diet, fasting, stress, anesthesia, heavy sedation, trailer rides

What foods are especially high in potassium and should be avoided in HYPP?

Alfalfa and molasses

How long do typical HYPP episodes last?

15–60 minutes

What can be seen early in a HYPP episode?

Myotonia, sweating, muscle fasciculations

What can severe HYPP cause?

Weakness, recumbency, respiratory distress, death

Is hyperkalemia always present when testing HYPP?

No

What is the definitive diagnostic test for HYPP?

Genetic testing

What sample is used for HYPP genetic testing?

20–30 mane or tail hairs with roots

What is a major prevention strategy for HYPP?

Decrease potassium intake

What other prevention strategy helps HYPP?

Regular exercise and minimizing stress

What drug can increase renal potassium loss in HYPP?

Acetazolamide

What is used during a severe HYPP episode to shift potassium into cells?

Dextrose

What can be given to raise the membrane threshold during HYPP?

Calcium gluconate

What may be needed if HYPP causes severe respiratory distress?

Tracheotomy

Is HYPP curable?

No, but it is manageable

What does GBED stand for?

Glycogen branching enzyme deficiency

What type of inheritance does GBED have?

Autosomal recessive

What age group is affected by GBED?

Foals

What happens to glycogen in GBED?

Normal glycogen branching is absent, causing abnormal unbranched glycogen

What is the prognosis for GBED?

Fatal

What are major clinical signs of GBED?

Weakness, seizures, hypothermia, collapse, cardiac/respiratory failure, sudden death

What is the difference between myopathy and rhabdomyolysis?

Myopathy is a general/milder muscle disease

What happens to muscle enzymes with rhabdomyolysis?

They increase significantly

What major secondary complication can occur with rhabdomyolysis?

Acute kidney injury

Is non-exertional rhabdomyolysis associated with exercise?

No

What infectious myopathy is emphasized?

Clostridial myositis

What type of bacteria cause Clostridial myositis?

Gram-positive anaerobic bacteria

How does Clostridial myositis commonly occur?

Deep inoculation after an IM injection or penetrating wound

What happens to the muscle in Clostridial myositis?

Rapid necrosis with gas production

What are early signs of Clostridial myositis?

Localized swelling, heat, and pain

What happens to the swelling as Clostridial myositis progresses?

It may become cool and gas-filled

What does gas in the muscle cause on palpation?

Crepitus

What may come from a needle aspirate?

Foul-smelling gas and fluid

What might ultrasound show with Clostridial myositis?

Fluid and hyperechoic gas

What happens systemically with severe Clostridial myositis?

Toxemia, depression, fever, shock

What are CK and AST in Clostridial myositis?

Moderately increased

How is Clostridial myositis diagnosed?

History/signs, ultrasound, aspirate, anaerobic culture

What is an important treatment for Clostridial myositis?

Aggressive antimicrobial therapy

What surgical treatment is used for Clostridial myositis?

Debridement/fenestration

What is the prognosis for Clostridial myositis?

Guarded to poor

What immune-mediated muscle disease is discussed?

Myosin Heavy Chain Myopathy

What gene is mutated in MyHM?

MyHM1

What breeds are especially associated with MyHM?

Quarter Horses and related breeds

What age groups are especially affected by MyHM?

What can trigger MyHM?

Infection or vaccination

What are the two clinical presentations of MyHM?

Immune-mediated myositis and non-exertional rhabdomyolysis

What is the classic sign of immune-mediated MyHM?

Muscle atrophy

What is the treatment for immune-mediated MyHM?

Dexamethasone followed by prednisolone

What nutritional deficiency causes nutritional myodegeneration?

Vitamin E and/or selenium deficiency

What type of horse is classically affected by nutritional myodegeneration?

Young, rapidly growing foals

What is Hypoglycin A myopathy associated with?

Seasonal pasture myopathy

What is exertional rhabdomyolysis?

Muscle injury/rhabdomyolysis associated with exercise

What are the three broad presentations of exertional rhabdomyolysis?

Sporadic, chronic, recurrent

What is sporadic exertional rhabdomyolysis?

A single episode with no previous episodes

What is recurrent exertional rhabdomyolysis (RER)?

Repeated episodes of rhabdomyolysis

What can chronic exertional myopathy look like?

Stiffness, reluctance to exercise, poor performance

What happens to CK with RER?

Repeated increases

What happens to CK with chronic myopathy such as MFM?

Often normal

What is the classical "tying up" presentation?

Painful, stiff horse reluctant to move after exercise