Equine Neurology Flashcards
CN I name and function
Olfactory nerve: mediates sense of smell
3 ways of testing CN II
Optic Nerve
i) drop a cotton ball and watch patient follow it to the ground (II only)
ii) Menace response (II for visual cues + VII for blink)
iii) PLR (II for visual + III for pupil constriction)
function of CN II
Optic nerve: carries visual signals from retina to occipital lobe of brain
2 ways of examining CN III function
Oculomotor nerve
i) observing for physiologic nystagmus when turning head
ii) observing pupillary constriction (PLR)
function of CN III
Oculomotor nerve; provides motor to most of the extraocular muscles (dorsal, ventral + medial rectus) + for pupil constriction
CN IV function
Trochlear nerve: provides motor function to the dorsal oblique extraocular muscle and rolls globe medially
Trochlear nerve CN number
CN IV
how to examine CN IV function
examine by observing for dorsolat. rotation of the pupil
3 branches of the CN V
trigeminal nerve: mandibular, maxillary, ophthalmic branches
function of CN V
Trigeminal nerve:
- motor to muscles of mastication (masseter, temporal)
- sensory: eyelids, cornea, tongue, nasal mucosa + mouth
What nerve are you assessing when checking jaw tone?
CN V: trigeminal nerve
What nerve are you assessing by touching the globe and assessing for retraction?
CN V: Trigeminal for sensory
CN VI: Abducens nerve for motor
What nerves are you assessing through the menace response?
CN II (optic) + CN VII (facial)
What nerves are you assessing when pinching the lips and observing for snarl response?
CN V (trigeminal) + CN VII (facial)
function of CN VI
Abducens nerve: provides motor function to the lateral rectus extra-ocular muscle and retractor bulbi
CN VII name and function
Facial Nerve: provides motor to muscles of facial expression (eyelids, ears, lips) + sensory to medial pinna. Also taste to rostral tongue + parasympathetic innervation to lacrimal glands and some salivary glands.
What nerve are you assessing when you observe for any facial paralysis, deviation of the nose to one side or droopy lips?
CN VII: facial
CN VIII name and function
Vestibulocochlear: sensory input for hearing and head position
CN IX name and function
Glossopharyngeal: provides motor and sensory innervation to pharynx for swallowing (w/ CN X).
Also innervates some salivary glands and provides taste innervation from caudal tongue.
What nerves are you assessing when you elicit a gag reflex?
CN IX: Glossopharyngeal
CN X: Vagus
CN X name and function
Vagus: innervates the larynx, oesophagus and pharynx. Also provides parasympathetic innervation to the heart and viscera.
how can you examine vagus nerve function?
CN X: Vagus nerve
i) elicit a gag reflex
ii) observe for laryngeal paralysis
iii) assess for megaoesophagus and regurgitation
name and function of CN XI
Spinal accessory: innervates cranial cervical muscles
name and function of CN XII
Hypoglossal: provides motor to the tongue
how do you examine CN XII
examine by observing tongue movements and symmetry or for problems drinking/prehending food
what is the tx and px for idiopathic trigeminal neuritis?
- supportive care w/ fluids and hand feeding of soft food
- prognosis is excellent w/ most dogs regaining function w/in 1-2wks and return to normal in 3-4wks
compare mortality rates of the togavirus encephalitides
Eastern equine encephalitis: 75-100% mortality
Venezuelan equine encephalitis: 40-80%
Western equine encephalitis: 20-50%
Dx of togavirus encephalitides
CS + CSF (inc. protein and cell count) + serology/necropsy evaluation
CS of togavirus encephalitides
- most profound in non-vax horses; fever, anorexia, depression, somnolence (sleeping sickness) to hyperasethesia, proprioceptive deficits, recumbency + cerebral/cranial nerve signs (head pressing, propulsive walking, circling, head tilt)
Dx of West Nile Virus
CS + CSF (inc. protein + mononuclear pleocytosis) –> antigen (IgM) capture ELISA, virus isolation + plaque reduction neutralisation
CS of WNV
- not all horses infected w/ WNV develop CS of disease. Horses that are vax. against WNV demonstrate decreased, if any, clinical manifestations. Those that do develop CS;
- depressed, ataxia, weakness, muscle fasciculations, fever, recumbency
CS of equine herpes myeloencephalitis
- fever, lethargy, depression
- ataxia, paresis, esp. Hind end
- urinary incontinence, loss of tail tone
- rarely concurrent resp. signs, can cause abortion in pregnant mares
Dx
Tx
Px
of equine herpes myeloencephalitis
Dx: nasal swab PCR
Tx: supportive care + antivirals
Px: fair depending on severity, but recovery is prolonged
CS of EPM
- chronic w/ mild/vague signs, unilat. hind-end m. atrophy, shifting leg/vague asymm. lameness, weakness, mild ataxia
- animals are almost always BAR
tx of EPM
Ponazuril (Marquis) tx up to 6months
what disease is prevented with opossum control?
EPM: Sarcocystis neurona
Pathogenesis of tetanus
Clostridium tetani enters through a wound (esp. anaerobic wounds) + proliferates to release a neurotoxin that travels to the CNS.
- Incubation period 1-3wks
prevention of tetanus
- annual tetanus toxoid vax., prophylactic tetanus antitoxin in unvax. horses w/ a wound
3 forms of rabies CS
i) Furious/cerebral form: odd/aggressive behaviour, self-mutilation, ataxia, vocalisation
ii) Dumb/brainstem form: somnolence, dementia, dysphagia, ataxia
iii) Paralytic/Spinal cord: progressive ascending paralysis
prevention of rabies
AAEP core annual/biannual vax
risk factors assoc. w/ botulism
silage, poorly stored forage, round hay bales
tx and px of botulism
Tx: botulinum antitoxin + supportive
Px: poor
pathogenesis of cauda equina
granulomatous perineuritis of peripheral nerves and cranial nerves, thought to be an immune-mediated event that may be triggered by other bacterial or viral infections
pathogenesis of equine degenerative myeloencephalopathy
EDM: Vit.E deficiency + a genetic component cause severe neuroaxonal dystrophy
pathogenesis of equine motor neuron disease
EMND: chronic Vit.E deficiency in adult horse causes peripheral motor neuron cell death
CS of EMND
weakness, low head carriage + high tail carriage muscle atrophy, muscle fasciculations, weight and muscle loss w/ good appetite
- NO ataxia
CS of wobblers
Cervical vertebral malformation
- usu. gradual but can be acute in onset
- ataxia, usu. worse in HLs than FLs dt HL innervation being SF in the spinal cord
- freq. perceived as poor performance/vague lameness
- no CN/brainstem signs
Dx of equine cervical vertebral malformation
Dx: Suspected based on signalment (young, rapidly growing horse) + CS (symmetric HL weakness and ataxia) + survey rads w/ or w//out myelopgraphy
i) Sagittal ratio is determined by measuring the smallest sagittal diameter of the vertebral canal of each cervical vertebra + dividing this number by the width of the cranial aspect of the vertebral body at its widest pt
ii) The sagittal ratio should be greater than 52% (C4-6) to 56% (C7)
iii) Myelographic studies are necessary for definitive ante-mortem diagnosis of CVM
