Exam 1 - Equine Neurology - Cervical Lesions, EPM, & Trauma Flashcards
what are the 2 fundamental objectives of a neurological exam?
- neurologic or not neurologic
- localize the lesion
ataxia is best defined as what?
inability to coordinate muscle activity during voluntary movement
T/F: cervical vertebral myelopathy & equine protozoal myeloencephalitis are associated with ataxia
true - usually but not always for equine protozoal myelitis
how is ataxia graded?
on a scale from 1-5
imprecise - subjective
what is the most common synonym for cervical vertebral myelopathy?
wobblers disease
what is cervical vertebral myelopathy?
abnormalities of the cervical vertebral body, processes, or foramina that cause compression of the cervical spinal cord at the level of 2 adjacent vertebrae
what is the most common form of cervical vertebral myelopathy? what animals does it affect?
dynamic - compression with neck movement
younger horses
where is the most common site of cervical vertebral myelopathy?
C3-C4 is most common followed by C6-C7
what is static cervical vertebral myelopathy?
osseous or soft tissue changes that compress the cord regardless of movement
what animals are affected by static cervical vertebral myelopathy?
typically older horses
where is the common site of static cervical vertebral myelopathy?
C5-C6
C6-C7
T/F: horses can have both dynamic & static forms of cervical vertebral myelopathy
true
what causes cervical vertebral myelopathy?
spinal cord compression from instability or malformation
what is the pathogenesis of cervical vertebral myelopathy?
unknown - probably multifactorial
what breeds may be predisposed to cervical vertebral myelopathy because of rapid growth?
thoroughbreds & warm bloods
T/F: cervical vertebral myelopathy is very similar to degenerative osseous diseae
True
what is the typical signalment of cervical vertebral myelopathy?
usually 6 months to < 3 years, quarter horses, thoroughbreds, warm bloods, & Tennessee walkers, maybe males
animals affected can be any age or breed
what is the common history in a patient with suspected cervical vertebral myelopathy?
can be acute - consider trauma
or can be subtle, slowly progressive
what are the clinical signs seen with cervical vertebral myelopathy?
bilateral symmetrical ataxia, paresis, & spasticity
what limbs are more severely affected by cervical vertebral myelopathy?
hindlimbs - usually at least 1 grade more severe
T/F: signs of cervical vertebral myelopathy tend to be stable but can be progressive, wax, or wane
true
what clinical signs will you see upon walking in a patient with suspected cervical vertebral myelopathy?
toe dragging, bunny hopping at canter, floating their front feet (can exacerbate this by elevating head), & a base wide stance at rest
how is cervical vertebral myelopathy diagnosed?
signalment/history, neuro exam, & radiographs
why can radiographs be useless in diagnosing cervical vertebral myelopathy?
cervical spine will often be normal in appearance
how is myelography used in diagnosing cervical vertebral myelopathy?
neutral & flexed views, 50% reduction in dorsal contrast column, but not perfect
what complications can occur with a myelogram?
poor recovery, worsening of signs after the procedure, seizures, & meningitis
what is the best treatment option for cervical vertebral myelopathy?
interbody fusion to stabilize the vertebrae & decompress the cord - patient selection is important
what are the limitations of using interbody fusion to treat cervical vertebral myelopathy?
complications, costs, missed sites
~70% of horses improve 1 grade of ataxia
what are the treatment options using dietary restrictions for cervical vertebral myelopathy?
decrease carbs & proteins to 66-75% of NRC requirements, add vitamins & minerals, stall rest
what is equine protozoal myeloencephalitis?
disease of horses in the americas associated with invasion of the central nervous system by apicomplexan protozoa
what is likely the most common neurological disease of horses in texas?
equine protozoal myeloencephalitis
what is the primary cause of equine protozoal myeloencephalitis?
sarcocytis neurona - vast majority
n. hughesii - some cases
what is the definitive host of sarcocystis neurona?
opossum
T/F: EPM is transmitted horse to horse
false - horses are the dead end host
how is EPM transmitted?
ingestion of food or water contaminated directly or indirectly with sporocysts from opossum feces
what horses are affected by EPM?
any breed, age, sex!! only in north & south america!
T/F: EPM is not reported in donkeys, mules, or non-horse equids
True
what is the classical presentation of EPM?
progressive, asymmetrical, multifocal, ataxia, & muscle atrophy
Why is equine protozoal myeloencephalitis the great imitator?
its clinical signs can represent a multitude of neurologic diseases
how is equine protozoal myeloencephalitis diagnosed postmortem?
looking for presence of protozoa - can be difficult if animal received treatment
which is more accurate in diagnosing equine protozoal myeloencephalitis, antemortem or postmortem?
post mortem
how is equine protozoal myeloencephalitis diagnosed antemortem?
use clinical signs, CBC, & CSF analysis to help rule-in or rule-out other causes
immunodiagnostic testing - serum or CSF
response to treatment - this can be misleading
what is an antemortem immunodiagnostic test for equine protozoal myeloencephalitis that is semi-quantitative?
western blot - looks for s. neurona specific antibodies
what is an antemortem immunodiagnostic test for equine protozoal myeloencephalitis that is quantitative & looks for s. neurona & s. hughesii?
indirect fluorescent antibody test
what is an antemortem immunodiagnostic test for equine protozoal myeloencephalitis that is quantitative & looks for s. neurona surface antigens?
ELISA
why is it best to test both serum & CSF for equine protozoal myeloencephalitis?
exposure is widespread so the seroprevalence is high
false negatives can occur in serum & CSF
negative results can make EPM less likely while positive results can be harder to interpret
what is the treatment for equine protozoal myeloencephalitis?
anti-protozoals, anti-inflammatory drugs, & other supportive care
what drug is used to treat equine protozoal myeloencephalitis once daily for a minimum of 3-4 months?
pyrimethamine (1mg/kg) & sulfonamide (25mg/kg) - ReBalance
what are the side effects/toxicities of pyrimethamine (1mg/kg) & sulfonamide (25mg/kg) - ReBalance?
diarrhea & bone marrow suppression (neutropenia & anemia)
what anti-protozoal treatment is used once daily for a duration of 28 days for equine protozoal myeloencephalitis?
Ponazuril
what are the benefits to using ponazuril for equine protozoal myeloencephalitis? cons?
corn oil may enhance intestinal absorption & side effects appear to be limited
expensive!!!
what drug is used to treat equine protozoal myeloencephalitis that has the same minimum treatment duration as ponazuril?
diclazuril
why are corticosteroids controversial for treating equine protozoal myeloencephalitis?
they may promote parasite proliferation by immunosuppression
what are the proposed benefits for using steroids for equine protozoal myeloencephalitis?
signs are largely attributed to inflammation associated with response to parasites - highly effective for acute CNS inflammation
what is the treatment outcome for equine protozoal myeloencephalitis?
1/3 recover
1/3 have no response to treatment
1/3 have deficits after treatment
10-30% relapse
how is equine protozoal myeloencephalitis prevented?
no vaccine!!!
opossum proof pastures & barns, store feed & hay in a secured manner, minimize stress
T/F: equine protozoal myeloencephalitis affects both gray & white matter (upper & lower motor neurons)
True
T/F: geographic distribution of equine protozoal myeloencephalitis appears to largely be attributed to the range of the opossum
true
T/F: sagittal ratios & using inter/intra vertebral measurements are believed to be helpful in making the diagnosis for cervical vertebral myelopathy - but don’t always identify the specific site of compression
true
if a horse with EPM has a subtle, slowly progressive onset of the disease, how do you expect the animal to present?
may appear to have a lameness problem initially
if a horse with EPM has an acute onset of the disease, how do you expect the animal to present?
sometimes associated with trauma & neurologic signs are errantly attributed to trauma
T/F: EPM can cause cranial nerve deficits
true
