Neuromuscular Disease in Small Animals Flashcards
what is the motor unit?
cell body in spinal cord
nerve root
spinal nerve
specific named nerve
synapse/junction
muscle fibers
what does it mean that myelinated nerves have saltatory conduction?
jump from one node of ranvier to the next
what is the rate of action potential travel influenced by?
diameter of axon and degree of myelination
how do the amount of acetylcholine receptors compare to the amount needed to generate an end-plate potential?
many more than required to reach action potential in the myofiber
how aree myofibers innervated?
each one innervated by only on axon of one motor neuron
what are some diseases that have an acute presentation?
myasthenia gravis
idiopathic polyradiculoneuritis
what is important about signalment?
breed
specific age groups
what are gait and posture like with neuromuscular disease?
lower motor neuron paresis without ataxia
crouched or plantigrade stance
cervical ventroflexion in cats
maybe worsens with exercise
should proprioception be normal or abnormal with neuromuscular disease?
normal with weight support
what are the goals of a workup for neuromuscular disease?
confirm neuromuscular localization
find level of lesion
define cause of lesion
determine treatment plan
what is important on a chem for diagnostics?
CK/AST
what does electrodiagnostic testing have a high degree of sensitivity for?
axonal dysfunction
what does electromyography record and study?
insertional, spontaneous and voluntary electrical activity of muscle
what can electromyography give insights into?
myopathies and neuropathies
what are abnormal electromyography findings?
spontaneous activity seen with no movement of the needle
what is evaluated for motor nerve conduction velocity?
CMAP amplitude: health of axons
nerve conduction velocity: degree of myelination
what are F waves?
antidromic motor nerve activation
what are diagnostics useful for in neuromuscular disease?
differentiate between denervation atrophy (axonal disease) and disuse atrophy
what is the other name of idiopathic polyradiculoneuritis?
coonhound paralysis
how can you diagnose idiopathic polyradiculoneuritis?
absent F waves
which nerves are affected first by geriatric onset laryngeal paralysis polyneuropathy?
longest ones: sciatic nerve and recurrent laryngeal nerve
what is the focal form or myasthenia gravis?
megaesophagus
what is the generalized form of myasthenia gravis?
megaesophagus
appendicular muscle weakness, exercise intolerance
normal spinal reflexes and muscle tone
what does acetylcholinesterase do?
enzymatic hydrolysis of unbound acetylcholine: rapid termination to ready muscle for next signal
what is the end-plate potential like at a normal neuromuscular junction?
several times larger than that required to reach action potential in the myofiber
what does the strength of muscle contraction depend on?
number of motor units activated in a muscle
what are some nerve changes due to damage?
demyelination
axonopathy
axonopath with secondary demyelination
wallerian degeneration
what is a polyneuropathy with acute presentation?
idiopathic polyradiculoneuritis
where in the neuromuscular junction is the problem in myasthenia gravis?
postsynaptic membrane
what does finding an elevated temperature, increased respiratory rate and/or effort, reduced chest excursions, or a palpable mass raise concern for?
aspiration pneumonia
hypoventilation
megaesophagus
what findings on physical exam would suggest cranial nerve deficits?
fatiguing or absent palpebral reflex
dysphagia
megaesophagus
voice change
inspiratory noise/stridor
what diagnostics for electrodiagnostic testing are useful for neuromuscular disease?
EMG
nerve conduction
what are myotonic discharges on EMG like?
waxing and waning
what is the most common cause of myotonic discharges on EMG?
myotonia congenita
what is motor nerve conduction velocity used in conjunction with?
EMG to differentiate neuropathies from myopathies
what does CMAP amplitude in motor nerve conduction velocity reflect?
health of the axons
what is repetitive nerve stimulation used to evaluate?
neuromuscular junction
what in repetitive nerve stimulation suggests myasthenia gravis?
decrement of greater than 10% of CMAP
what are the clinical signs of idiopathic polyradiculoneuritis?
reduced or absent spinal reflexes
reduced muscle tone
who does geriatric onset laryngeal paralysis polyneuropathy usually occur in?
geriatric (8-13) large breed dogs
what is the result of geriatric onset laryngal paralysis polyneuropathy?
distal axonopathy with secondary demyelination
what are the late clinical signs of geriatric onset laryngeal paralysis polyneuropathy?
laryngeal weakness or paralysis
paraparesis
abnormal withdrawal reflex
what are the acquired forms of myasthenia gravis?
idiopathic
paraneoplastic: thymoma
what is the acute, fulminating form of myasthenia gravis?
megaesophagus
appendicular muscle weakness, exercise intolerance
decreased or absent spinal reflexes, decreased muscle tone
hypoventilation, respiratory failure
