Exam 1 - Generalized Neuromuscular Disease Flashcards
what is a differential for acute disease of the muscle in generalized neuromuscular disease?
polymyositis
what are differentials for acute disease of the neuromuscular junction in generalized neuromuscular disease?
tick paralysis
botulism
myasthenia gravis
what are differentials for acute disease of the nerves in generalized neuromuscular disease?
acute idiopathic polyradiculoneuritis - coonhound paralysis
infectious causes
what is a differential for acute disease of alpha motor neurons in generalized neuromuscular disease?
myelitis - especially rabies
what neuromuscular diseases may present acutely non-ambulatory tetraplegic & will mimic a high cervical fracture or severe brain injury prior to the neuro exam?
tick paralysis, botulism, myasthenia gravis, acute idiopathic polyradiculoneuritis, & myelitis (rabies)
what should be in the standard diagnostic work-up for neuromuscular disease?
history of prescription drugs
CBC/chem with creatine kinase
met check - chest rads to r/o megaesophagus, thymoma, & aspiration pneumonia & abdominal ultrasound/rads
endocrine testing - thyroid & hyperadrenocorticism
what makes up a lower motor neuron unit?
cell body (CNS), axon (PNS - ventral root, nerve), muscle, & neuromuscular junction
how do patients with acute idiopathic polymyositis present clinically?
weakness, stilted gait, atrophy, inability to open jaw, megaesophagus, & dysphonia
what lab abnormalities may be seen with acute idiopathic polymyositis?
creatine kinase is typically very high
inflammatory leukogram is possible
negative paired infectious disease titers
how is acute idiopathic polymyositis diagnosed?
muscle biopsy is supportive
how is acute idiopathic polymyositis treated?
immunosuppression - corticosteroids are the 1st line
azathioprine as a 2nd line or adjunct treatment
how is acute idiopathic polymyositis monitored?
serial CKs to monitor remission
what are some causes of infectious polymyositis?
neospora - dog
toxoplasma - dog & cat
hepatozoon - dog
FIV - cat
sarcocytis - dog
in a patient with suspected infectious polymyositis, what do you expect the nature of their history to be?
chronic problem
tick paralysis effects what part of the neuromuscular system?
pre-synaptic neuron
what is the typical onset of tick paralysis?
3-7 days
T/F: the absence of ticks on a dog rules out tick paralysis
false
how is tick paralysis treated?
pull the ticks, treat with acaricides, & shave long thick coats
what diagnostics should be done for a suspected tick paralysis case?
bloodwork & CSF tap - usually normal
thoracic radiographs
patient gets better upon removal of ticks
what is the agent that causes botulism?
clostridium botulinum
what is the pathogenesis of botulism?
blocks the release of ACh at the presynaptic membrane of the neuromuscular junction
how is botulism diagnosed?
usually based on history & clinical signs
bloodwork & CSF are typically normal
how is botulism treated?
supportive care
recovery can take weeks
what is the most common type of myasthenia gravis in dogs?
acquired form
what is the pathogenesis of acquired myasthenia gravis?
autoantibodies are directed against the acetylcholine receptors at the neuromuscular junction
what are the clinical signs of acquired myasthenia gravis in dogs?
muscular weakness & excessive fatiguability - ocular, facial, oropharyngeal, esophageal, & limb musculature
what is the pathogenesis of congenital myasthenia gravis?
animal is born with too few acetylcholine receptors
in working up a suspected myasthenia gravis dog, what is the first step?
take radiographs
use to use tensilon but not much anymore
in working up a suspected myasthenia gravis dog, what is the second step?
determining if it is congenital or acquired
how is congenital myasthenia gravis diagnosed?
intercostal muscle biopsy
how is acquired myasthenia gravis diagnosed?
acetylcholine receptor antibody test
met screen
thyroid problems (thymoma)
this condition often occurs secondary to what neuromuscular disease?
myasthenia gravis
how is myasthenia gravis in dogs treated?
anti-acetylcholinesterase meds probably for life
bailey chair feedings - avoid problems with megaesophagus/aspiration pneumonia
serial AChR Ab titers to monitor
T/F: 50-60% of dogs diagnosed with myasthenia gravis die within 1 year of the diagnosis
true
what kind of disease is idiopathic acute polyradiculoneuritis?
acquired demyelinating disease
what does idiopathic acute polyradiculoneuritis affect?
spinal nerve roots
what is the typical presentation of a dog with idiopathic acute polyradiculoneuritis?
rapid (12-24 hour) onset of ascending flaccid paralysis
how is idiopathic acute polyradiculoneuritis diagnosed?
history of exposure - bloodwork & CK are often normal, CSF often has elevated protein
EMG, NCV, & muscle/nerve biopsy
how is idiopathic acute polyradiculoneuritis treated?
supportive care
what bacteria causes idiopathic acute polyradiculoneuritis
campylobacter
what is the pathogenesis of rabies?
virus enters body through saliva/CSF/CNS tissue of infected animal & migrates up the nerves to the spinal cord & then travels to the brain & then down from cranial nerves
viruses arrives in saliva - animal is now infectious
what are the infectious materials that can spread rabies?
saliva, CNS tissue, & CSF
what is the latency period of rabies?
2-26 weeks
between dogs & cats, which are more likely to be affected by rabies?
dogs more so than cats
T/F: once clinical signs of rabies begin, death occurs within 7-10 days
what may be the first clinical sign seen with rabies?
ascending lower motor neuron paresis
what disease is an important consideration in a patient presenting with acute, progressive, neurological signs?
rabies
what are some general clinical signs of rabies?
altered mentation, CN paresis, multifocal/diffuse neurological signs
what is the typical history of an animal infected with rabies?
outdoor, unvaccinated animal presenting with progressive disease
what would you expect your results to be in evaluating CSF in a rabies patient?
lymphocytic pleocytosis
what is the gold standard for rabies diagnoses?
IFA virus detection in the brain - negri bodies may be seen in later parts of the disease
what is this? what disease is it common in?
negri body - rabies
T/F: titers are diagnostic for diagnosing rabies
false
how can rabies be diagnosed in humans?
skin biopsies
how do you make a definitive diagnosis of rabies?
necropsy of the animal to look at the brain
what is the recommended treatment for rabies?
euthanasia
why not freeze or shoot a rabies suspect?
need the brain intact for samples
if a vaccinated animal is bitten by a rabies suspect, what should happen?
quarantined for 45 days and boostered
if a rabies vaccinated animal bites a person, what should be done? what if they are unvaccinated?
observed for 10 days for signs of rabies
what should you do if a wild animal bites a person? why?
euthanize!
any animal that has bitten people & has neurological signs compatible with rabies
if an animal that is unvaccinated is bitten by an animal known to have rabies, what should you do?
vaccinate & quarantined for 6 months or euthanized
what are some less common differentials for acute neuromuscular disease?
coral snake envenomation
blue green algal intoxications
black widow spider envenomation
rare toxicities - lasalocid & other ionophores
an animal presents with acute flaccid non-ambulatory tetraparesis, on physical exam/neuro exam, you find that the animal has a weak gag reflex and signs of regurgitation, what are the two diagnostics you’ll pursue next?
thoracic rads & arterial blood gas
an animal presents with acute flaccid non-ambulatory tetraparesis, on physical exam, its respirations are showing weak chest inspiratory expansion, open-mouth breathing, & labored respirations, what two diagnostics will you pursue next?
thoracic rads & arterial blood gas
why would you pursue thoracic rads & arterial blood gas in an animal presenting with acute flaccid non-ambulatory tetraparesis with labored breathing & regurgitation/weak gag reflexes?
looking for megaesophagus/aspiration pneumonia & to see if the animal is ventilating well
an animal presents with acute flaccid non-ambulatory tetraparesis has a PaCO2 > 45mmHg, what should you consider?
mechanical ventilation
an animal presents with acute flaccid non-ambulatory tetraparesis has a PaCO2 < 45mmHg, what should you consider?
monitor their breathing pattern & blood gases every 4-6 hours & provide O2 supplementation
an animal presents with acute flaccid non-ambulatory tetraparesis has megaesophagus & aspiration pneumonia, what are your next steps?
avoid oral feeding - consider an NG or G tube
check AChAb titers
provide O2 supplementation
what are the 8 main categories of chronic generalized LMN disease for differentials?
- endocrine
- infectious
- non-infectious inflammatory
- paraneoplastic
- metabolic
- degenerative
- drug-related
- idiopathic
what chemo drugs may cause neuromuscular problems?
cisplatin & vincristine
T/F: certain antibiotics cause neuromuscular junction blocking effects
true
what 5 antibiotic classes can cause neuromuscular junction blocking effects?
- aminoglycosides - gentamycin
- lincomycin - precursor to clindamycin
- penicillamine
- polymixins
- tetracyclines
what cancer is most frequently identified in causing polyneuropathy?
insulinomas
other than insulinomas, what cancer can cause polyneuropathy?
lymphoma
what cancer causes myopathy in boxers?
lymphoma
what tumor can cause an associated myopathy?
thymoma
T/F: myasthenia gravis can occur secondary to neoplasia and affect the neuromuscular junction
true - common with thymomas
what is myotonia?
disturbance in muscle relaxation after voluntary contraction or percussion
congenital myotonia typically affects what animals?
young dogs
acquired myotonia can be caused by what drug?
glucocorticoids
what causes congenital myotonia?
malformation in the chloride channels which can cause constant contraction of voluntary muscles
what is the typical presentation of a dog with congenital myotonia?
sudden onset stiffness with intact consciousness
what is the typical presentation of acquired myotonia?
stiff, stilted gait
what breed is associated with hypokalemic myopathy?
burmese cats
what is the pathogenesis of hypokalemic myopathy?
hyperpolarization of the sarcolemma resting membrane prevents muscle contraction
T/F: hypokalemic myopathy may be associated with renal disease, diet, and hyperthyroidism in cats
true
what disease has this typical presentation
hypokalemic myopathy
what is the pathogenesis of hyperkalemia causing neuromuscular problems?
membrane depolarization - leads to weakness, bradycardia, & atrial standstill
what are 2 examples of metabolic diseases that have hyperkalemia?
post-renal disease & addisons
what is the pathogenesis of hypocalcemia causing neuromuscular problems?
calcium interacts with sodium channels to reduce excitability & threshold - depolarization leads to weakness, tetany, tremors, tachycardia, hyperthermia, & seizures
what is the pathogenesis of hypomagnesemia causing neuromuscular problems?
Mg is a part of an ATP molecule, so low Mg causes weakness, tremors, seizures, cardiac arrhythmias secondary to energy depletion (similar to grass staggers)
what is the most common lab abnormality in critically ill patients?
hypomagnesemia
what electrolyte abnormality may be common in brachycephalic dogs?
hypomagnesemia
what diagnostic test may I use to rule in polymyositis?
creatine kinase
if i’m concerned about disease affecting the neuromuscular junction, what diagnostics and history questions would be helpful?
tick search/tick treatment - treat regardless
myasthenia gravis titers & chest rads
carrion or garbage eater - botulism
how can hypoglycemia cause LMN disease signs?
ATP depletion - weakness and seizures as a result
what are your top 6 differentials for neuromuscular disease?
- rabies
- coonhound paralysis
- tick paralysis
- myasthenia gravis
- myositis
- botulism