Large Animal Neuromuscular Disease Flashcards
what are some clinical exam findings of a lumbar-sacral plexus (femoral nerve) lesion?
inability to extend and fix stifle
collapse or buckling of hind
patella reflex absent or decreased
analgesia or anesthesia of medial rear limb
what are some causes of a lumbar-sacral plexus (pelvic nerve) lesion?
over-stretching of limb
pelvic fracture
EPM (multifocal)
what can cause a lumbar-sacral plexus lesion that affects the obturator nerve?
dystocia
splay-legging on slippery surfaces
what can cause a traumatic nerve injury?
compression of nerves against bone during dystocia
what does a compressive injury cause?
demyelination of neurons
what do many cases of calving paralysis involve?
simultaneous damage to both obturator and femoral/sciatic nerrves
what does the radial nerve innervate?
flexor of shoulder
extensors of elbow, carpus, digit
what might sensory deficits in radial nerve paralysis include?
loss of sensation dorsal and lateral aspects of forelimb
what do low lesions in radial nerve paralysis cause?
knuckling carpus, fetlock, and pastern
can bear weight if joints splinted
at what rate does axonal regeneration occur?
1 mm/day or 1 inch/month
what is equine motor neuron disease?
diffuse neurodegenerative disease: lower motor neurons of spinal cord grey matter
what is dysfunction and death of motor neurons in equine motor neuron disease associated with?
vitamin E deficiency: oxidative disorder
is a heritable predisposition shown in horses with equine motor neuron disease?
not proven
where are lesions in equine motor neuron disease?
ventral horn cells of spinal gray matter
sometimes selective nuclei of cranial nerves
what are the clinical signs of equine motor neuron disease subacute form?
trembling/fasciculation
limbs gathered close
weight shifting of rear limbs
low head carriage
weight loss
what are the clinical signs of equine motor neuron disease chronic form?
muscle atrophy (usually symmetric)
tail held abnormally high resting position
what are the three major manifestations of botulism?
ingestion preformed toxin
wound botulism
toxicoinfectious “shaker foal” syndrome
how many toxins are identified in Clostridium botulinum infection?
eight
what type of botulism toxin are horses usually affected by?
type B toxin: forage
what leads to toxicoinfectious botulism?
ingestion of Clostridium botulinum spores
what does the botulism toxin do?
binds to presynaptic receptors, transslocates into presynaptic nerve terminus, and prevents acetylcholine release (cleaves SNARE proteins)
induces neuromuscular blockade
how can you treat botulism?
botulism antitoxin +/- antibiotics
what is the etiological agent of tetanus?
Clostridium tetani
what is Clostridium tetani?
gram positive anaerobic bacterium
what is the process of a Clostridium tetani spore infecting an animal?
enter wounds or incisions
convert to vegetative state and replicate
produce toxin within 4-8 hours
what are the two toxins in tetanus?
tetanolysin: exotoxin
tetanospasmin: neurotoxic exotoxin
how long do tetanus toxins remain bound to the interneuron?
3 weeks
what are the early clinical signs of tetanus?
stiff gait
muscle fasciculations
what is the prognosis of tetanus?
guarded even with treatment
what nerves are damaged in calving paralysis?
often both obturator and femoral/sciatic nerves
what are the differentials for a down cow post calving?
pelvic or femoral fractures
dislocation of coxofemoral joint
separation of pelvic symphysis
hypocalcemia
endotoxemia from toxic metritis/mastitis
when is radial nerve paralysis seen?
usually after general anesthesia, prolonged lateral recumbency
what can be seen in the retina with equine motor neuron disease?
lipofuscin pigment accumulates in retina
do horses with equine motor neuron disease walk or stand better?
walk better
how can botulism be diagnosed?
grain test
forage/sample analysis
