Localization Syndromes

Question 1

What is localization syndrome? sites?

Answer 1

• Myopathic
• Neuropathic
• Spinal Cord
  
  • Lumbosacral
  • Thoracolumbar
  • Cervicothoracic
  • Cervical
• Pontomedullary
• Midbrain
• Cerebral
• Cerebellar
• Hypothalamic
• Vestibular
• Multifocal

Question 2

What is Myopathic Syndrome

Answer 2

• Generalized weakness
• Exercise intolerance
• Stiff, stilted gait
• Muscle atrophy or hypertrophy
• Muscle pain
• Limited joint movement late in the disease
• Reflexes are preserved

Question 3

What is the diagnostic approach to myopathies

Answer 3

• CBC, Chemistry, UA, T4, etc
• Clinical characteristics and reported diseases
• Disease specific testing (serological, genetic)
• EMG
• Muscle biopsy

Question 4

What is Immune-mediated Polymyositis? CK? Dx? Tx?

Answer 4

• Immune-mediated, inflammatory
• Middle-aged, large breed dogs
• Weakness worse with exercise
• CK: usually elevated
• DX: EMG, Biopsy, ANA
• TX: immunosuppression
  
  • Prednisone - rapid response
  • Azathioprine, Cyclosporine
  • Leflunomide, Mycophenolate
• General:
  
  • Not common
  • Vague nature of the exercise intolerance can be misleading
  • May not have any noticeable muscle pain
  • If the Serum biochemistry profile does not include CK, this disease may never be suspected
  • DDx: myasthenia gravis
    
    • Test with pyridostigmine -MG responds IMP do not
      *

Question 5

What is Masticatory myositis? Dx? DDx?

Answer 5

• The most common myopathy of dogs
• Immune-mediated myositis
• Large breed dogs
• Early: hypertrophy, pain of masticatory muscles, pain on opening mouth, ocular signs
• Late: atrophy of muscles, fibrosis, inability to open mouth (trismus)
• Dx:
  
  • CBC, Chem, UA - All normal
  • EMG - myopathic potentials
  • Histopathology - rarely done
  • Serum anti-2M antibodies
• DDx: (early/painful)
  
  • Retrobulbar abscess
  • TMJ disease
  • Otitis externa/media

Question 6

What is the treatment for masticatory myositis

Answer 6

• Prednisone
  
  • 2mg/kg/day for 4-6 weeks, gradual reduction (25% every 4 weeks)
  • May be sufficient therapy
• Cyclosporine, Leflunomide, Azathioprine, Mycophenolate
  
  • Used when side effects of prednisone are intolerable or corticosteroid use is contraindicated
  • Used when patients relapse on reduction of prednisone
  • Commit to minimum 12-month use

Question 7

What is Exercised-induced Collapse?

Answer 7

• (Was) common in Labrador retrievers
  
  • mutation of DNM1 gene
  • Defect in nerve communication during exercise
  • Autosomal recessive
• Clinical signs:
  
  • onset 5mo - 3yo
  • Usually fit, muscular, excitable
  • Weakness and collapse after 5-20 minutes of strenuous exercise
  • High rectal temperature (>107)
• Dx:
  
  • Genetic testing at U of M
• Therapy:
  
  • Avoid trigger activity
• No longer common and may be come even less common with routine genetic screening and selective breeding. The dramatic nature of the collapse ad the impact it has on the intended use of the dog is an impetus of eliminating form the gene pool
• Dogs with collapse that are not DNM-1 defective seem to have less severe clinical signs and there is likely less pressure to exclude them from a breeding program

Question 8

What is Steroid Myopathy? Dx? Tx?

Answer 8

• Seen in Cushing’s disease, Iatrogenic
• Signs: also PU/PD, pendulous abdomen, alopecia
• Generalized muscle atrophy (rarely myotonia)
• Dx: increase CK, increased SAP; EMG
• Tx: discontinue steroid, treat Cushings

Question 9

What is Hypothyroid Myopathy?

Answer 9

• Other signs present:
  
  • alopecia, weight gain, inactivity,
  • Hypercholesterolemia, mild anemia
  • Myxedema
• Muscle atrophy
• Dx: measure total T4
• Tx: supplement

Question 10

Name some Myopathic Disorders?

Answer 10

• Muscular Dystrophy
• Labrador myopathy (centronuclear myopqathy)
• Distal myopathy of Rottweilers
• Canine Stress Syndrome
• Myotonia congenita
• Fibrotic myopathy
• Nemaline myopathy
• Inclusion myopathy
• Episodic muscle hypertonicity
• Lipid storage, Glycogen storage
• Ischemic myopathy

Question 11

What is Feline Hypokalemic Polymyopathy?

Answer 11

• Clinical signs:
  
  • ventroflexion of the neck
  • muscle weakness
• Usually have chronic renal failure
• DDx:
  
  • Thiamine deficiency
  • Feline idiopathic polymyositis
• Serum potassium not always low
• Common problem in practice: if you see old cats with chronic kidney disease you will see old cats with low potassium. Generally, this is a preventable disease for those cats with routine visits as most of these cats have had bloodwork done sometimes in the past that showed a serum potassium <4.
• Another reason one has to be careful with subcutaneous fluid therapy to the old cat with CKD. Borderline potassium can be driven way below the threshold and a crisis created very quickly
• If potassium is low, MP is high, and BUN and Creatinine are not exciting think primary aldosteronism

Question 12

What is Myasthenia Gravis? how is it diagnosed?

Answer 12

• Neuromuscular junction disorder
• Congenital:
  
  • absence of ACh receptors
  • Jack Russell terrier, Smooth fox terrier
• Acquired:
  
  • Antibodies against the receptor
  • Idiopatic / Secondary to Thymoma
• Generalized weakness
  
  • worse with exercise
  • better with rest
• Normal spinal reflexes
• Focal MG: megaesophagus, pharyngeal dysfunction
• Dx:
  
  • Detect ACh receptor antibodies
  • Tensilon test (no longer available)
  • Nerve stimulation
• Fulminant from often presents with an inability to recover with rest and megaesophagus is also typically present
• Fluoroquinonolone antibiotics can interfere with N0M transmission and may exacerbate MG

Question 13

What is the treatment for Myasthenia Gravis?

Answer 13

• Pyridostigmine bromide
  
  • Oral anticholinesterase
  • Start low does, gradually increase
  • Does not improve esophageal motility
• Immunosuppression
  
  • Corticosteroids
    
    • Generally not recommended as they may worsen weakness or aggravate pneumonia
    • limited to pyridostigmine-resistant MG
  • Azathioprine, Cyclosporine, Mycophenolate, Leflunomide
    
    • Limited evidence for the efficacy of any o fthese drugs to convert the patient to a negative status and costs/side effects may be significant
    • Spontaneous resolution of disease may happen with no therapy given
• Plasmapharesis, Thymectomy