Canine Flash Notes - Myasthenia Gravis

Question 1

a 6-year-old female spayed GSD presents with exercise intolerance & regurgitation. what 4 tests should be performed when working her up?

Answer 1

minimum database - CBC/chem/UA

acetylcholinesterase antibody test

thoracic radiographs to evaluate the patient for aspiration pneumonia & megaesophagus

tensilon test - not done as commonly due to the risk of cholinergic crisis, but ultra-short acting acetylcholinesterase that prolongs the availability of acetylcholine & improvement of gait disturbances within 1 minute

Question 2

what treatment should be utilized for a dog with myasthenia gravis, megaesophagus, & aspiration pneumonia?

Answer 2

cholinesterase inhibitors to inhibit/breakdown acetylcholine (pyridostigmine)

bailey chair feedings for megaesophagus

empirical antibiotics for the aspiration pneumonia - nebulization & coupage

Question 3

what communication should be made to the owner of a GSD with myasthenia gravis, megaesophagus, & aspiration pneumonia as far as long term outlook goes?

Answer 3

fair prognosis if treatment is started early, but 1 year mortality rate is 40-60% among all dogs!!

warn owner of the risks - multiple hospitalizations & high risk of aspiration pneumonia

Question 4

what causes congenital MG?

Answer 4

inadequate number of post-synaptic nicotinic acetylcholine receptors

RARE

Question 5

what is the most common form of myasthenia gravis?

Answer 5

acquired

Question 6

what breeds are predisposed to developing congenital myasthenia gravis?

Answer 6

RARE

jack russels & smooth haired mini dachshunds

Question 7

what breeds are predisposed to developing acquired myasthenia gravis? what causes it?

Answer 7

GERMAN SHEPHERDS

goldens, labs, & abyssinian cats

autoimmune disease - antibodies bind the post-synaptic acetylcholine receptors in striated muscle causing them to be internalized

Question 8

what clinical signs are associated with focal myasthenia gravis?

Answer 8

megaesophagus, facial weakness, & laryngeal paralysis

Question 9

what clinical signs are associated with generalized myasthenia gravis?

Answer 9

generalized weakness, paraparesis, or tetraparesis

Question 10

what clinical signs are associated with myasthenia crisis?

Answer 10

acute tetraparesis, megaesophagus, & respiratory distress

Question 11

what is the gold standard diagnostic test for acquired myasthenia?

Answer 11

acetylcholinesterase antibody test

Question 12

what is the treatment of choice for myasthenia gravis?

Answer 12

pyridostigmine - cholinesterase inhibitor