Large Animal Neuromuscular Disease

Question 1

what are some clinical exam findings of a lumbar-sacral plexus (femoral nerve) lesion?

Answer 1

inability to extend and fix stifle
collapse or buckling of hind
patella reflex absent or decreased
analgesia or anesthesia of medial rear limb

Question 2

what are some causes of a lumbar-sacral plexus (pelvic nerve) lesion?

Answer 2

over-stretching of limb
pelvic fracture
EPM (multifocal)

Question 3

what can cause a lumbar-sacral plexus lesion that affects the obturator nerve?

Answer 3

dystocia
splay-legging on slippery surfaces

Question 4

what can cause a traumatic nerve injury?

Answer 4

compression of nerves against bone during dystocia

Question 5

what does a compressive injury cause?

Answer 5

demyelination of neurons

Question 6

what do many cases of calving paralysis involve?

Answer 6

simultaneous damage to both obturator and femoral/sciatic nerrves

Question 7

what does the radial nerve innervate?

Answer 7

flexor of shoulder
extensors of elbow, carpus, digit

Question 8

what might sensory deficits in radial nerve paralysis include?

Answer 8

loss of sensation dorsal and lateral aspects of forelimb

Question 9

what do low lesions in radial nerve paralysis cause?

Answer 9

knuckling carpus, fetlock, and pastern
can bear weight if joints splinted

Question 10

at what rate does axonal regeneration occur?

Answer 10

1 mm/day or 1 inch/month

Question 11

what is equine motor neuron disease?

Answer 11

diffuse neurodegenerative disease: lower motor neurons of spinal cord grey matter

Question 12

what is dysfunction and death of motor neurons in equine motor neuron disease associated with?

Answer 12

vitamin E deficiency: oxidative disorder

Question 13

is a heritable predisposition shown in horses with equine motor neuron disease?

Answer 13

not proven

Question 14

where are lesions in equine motor neuron disease?

Answer 14

ventral horn cells of spinal gray matter
sometimes selective nuclei of cranial nerves

Question 15

what are the clinical signs of equine motor neuron disease subacute form?

Answer 15

trembling/fasciculation
limbs gathered close
weight shifting of rear limbs
low head carriage
weight loss

Question 16

what are the clinical signs of equine motor neuron disease chronic form?

Answer 16

muscle atrophy (usually symmetric)
tail held abnormally high resting position

Question 17

what are the three major manifestations of botulism?

Answer 17

ingestion preformed toxin
wound botulism
toxicoinfectious “shaker foal” syndrome

Question 18

how many toxins are identified in Clostridium botulinum infection?

Answer 18

eight

Question 19

what type of botulism toxin are horses usually affected by?

Answer 19

type B toxin: forage

Question 20

what leads to toxicoinfectious botulism?

Answer 20

ingestion of Clostridium botulinum spores

Question 21

what does the botulism toxin do?

Answer 21

binds to presynaptic receptors, transslocates into presynaptic nerve terminus, and prevents acetylcholine release (cleaves SNARE proteins)
induces neuromuscular blockade

Question 22

how can you treat botulism?

Answer 22

botulism antitoxin +/- antibiotics

Question 23

what is the etiological agent of tetanus?

Answer 23

Clostridium tetani

Question 24

what is Clostridium tetani?

Answer 24

gram positive anaerobic bacterium

Question 25

what is the process of a Clostridium tetani spore infecting an animal?

Answer 25

enter wounds or incisions
convert to vegetative state and replicate
produce toxin within 4-8 hours

Question 26

what are the two toxins in tetanus?

Answer 26

tetanolysin: exotoxin
tetanospasmin: neurotoxic exotoxin

Question 27

how long do tetanus toxins remain bound to the interneuron?

Answer 27

3 weeks

Question 28

what are the early clinical signs of tetanus?

Answer 28

stiff gait
muscle fasciculations

Question 29

what is the prognosis of tetanus?

Answer 29

guarded even with treatment

Question 30

what nerves are damaged in calving paralysis?

Answer 30

often both obturator and femoral/sciatic nerves

Question 31

what are the differentials for a down cow post calving?

Answer 31

pelvic or femoral fractures
dislocation of coxofemoral joint
separation of pelvic symphysis
hypocalcemia
endotoxemia from toxic metritis/mastitis

Question 32

when is radial nerve paralysis seen?

Answer 32

usually after general anesthesia, prolonged lateral recumbency

Question 33

what can be seen in the retina with equine motor neuron disease?

Answer 33

lipofuscin pigment accumulates in retina

Question 34

do horses with equine motor neuron disease walk or stand better?

Answer 34

walk better

Question 35

how can botulism be diagnosed?

Answer 35

grain test
forage/sample analysis