Various Issues in Equine Neurology Flashcards
What is Horner Syndrome?
sympathetic dysfunction resulting in interruption of the ocular pathway at the brainstem, spinal cord, spinal nerves, cervical sympathetic trunk, and cranial cervical ganglia in the skull
What are the 2 most common causes of Horner Syndrome? What are some other causes?
- otitis media
- IV injection complication
- guttural pouch infection
- trauma at eh basisphenoid area
- abscess, tumor, or other space-occupying lesion
- esophageal rupture
- carotid artery ligation
What are the 3 ocular signs of Horner Syndrome? What else is commonly seen?
- miosis
- ptosis
- eye retraction and protrusion of 3rd eyelid
(normal menace and palpebral reflexes)
hyperthermia - sweating, congestion
What 2 pharmacologic testings are used to diagnose Horner Syndrome?
- hydroxyamphetamine
- epinephrine or phenyephrine
if Horner’s, ocular signs will resolve
When is Horner Syndrome reversible?
if caused by Xylazine injection
- usually irreversible with symptomatic treatment
What results from facial nerve paralysis? What are 4 common etiologies?
paralysis of the facial expression muscles - eyelids, lips, ears, nose
- facial nerve compression by halter
- inflammation - GP, EPM
- encephalitis
- tumor
What are the 4 most common clinical signs associated with facial nerve paralysis?
- droopy ears, eyelids, nose, and lips
- absent palpebral and menance response
- corneal ulcer due to inability to blink
- vestibular signs
What is the vestibular system responsible for?
- maintenance of balance
- reflex orientation to gravitational forces
- appropriate eye, head, and trunk position
What causes temporohyoid osteoarthropathy (THO)?
periosteal reaction and enlargement associated with the stylohyoid, tympanic bulla, and petrous portion of the temporal bone, which causes sclerosis and fusion between the skull and hyoid apparatus
What is indicative of peripheral vestibular disease? What are 3 common etiologies?
acute onset of vestibular disease with facial nerve paralysis
- THO - extention of inflammation, bony changes, fx
- head trauma
- drug toxicity
What breed seems to be overrepresented with peripheral vestibular disease? What risk factor increases its occurance?
AQH
veterinary procedures where the mouth is left open and tongue is held outside of the mouth for long periods of time - dentals, NG tube passage
What are some signs of peripheral vestibular disease?
- head tilt toward the lesion**
- contralateral hypertonia/hyperreflexia
- nystagmus, strabismus
- falling, circling
- reluctance to move
- asymmetric ataxia with preserved strength
- facial nerve paralysis
- violence and disorientation
How does central vestibular disease compare to peripheral vestibular disease?
- proprioceptive deficits
- other cranial nerves affected (other than facial)
- altered mentation —> more depressed
- nystagmus - horizontal, rotatory, vertical, fast away
What is commonly seen on radiographs and endoscopy in cases of vestibular disease?
RADIOGRAPHS - thickened, enlarged tympanic bulla
ENDOSCOPY - stylohyoid enlargement seen in guttural pouch
What treatments are recommended for vestibular disease? What surgical procedures can be performed?
- stabilization, decrease inflammation
- broad spectrum AB
- treat exposure keratitis and keratoconjunctivitis sicca with eye ointments (typically containing AB and steroids)
partial stylohyoid ostectomy or ceratohyoidectomy
What is the most common cause of abnormal head shaking?
trigeminal-mediated involuntary sudden violent and repetitive movement of the head with rubbing, snorting, and anxiety —> horse typically becomes un-rideable
What are the 2 types of head shaking?
- symptomatic - identifiable physical cause where removal of issues resolves the issue
- idiopathic - no discernable cause with continuation of signs
What horses seem to have increased incidences of head shaking? What are some common triggers?
pleasure horses
- light
- sound
- stress
- neck flexion
What are some potential causes of head shaking?
- programmed for head shaking
- rhinitis - allergic, vasomotor, light-sensitive
- skull lesions - THO, guttural pouch mycosis
- eye: floaters, cystic corpora nigri, blocked duct
- ear mites
- dental/sinus issues
- cervical arthritis
89% found no cause
What workup is recommended to find the cause of head shaking?
- history (video!) and physical exam
- ophthalmic exam
- neurologic exam
- dental exam
- endoscopy
- radiographs
- nerve block trial
What physical treatments are recommended for head shaking?
- muzzle nets
- facemask
- contact lenses
- bitless bridles
What are 4 options for medical management of head shaking?
- cyproheptadine, carbamazepine, gabapentin
- corticosteroids, antihistamines
- melatonin, supplements, acupuncture, chiro
- electric nerve stimulation
What is dysphagia? What is the most common cause?
abnormality in prehension, mastication, and swallowing
neurologic
What is the most common side clinical sign of Stringhalt? What tends to worsen this?
sudden onset of abrupt hyperflexion of the hock or stifle where limbs snap forward and upward (in adduction)
- backing
- turning
- walking on a slope
- stress
- cold weather
What are the 3 classifications of nerve injuries?
- neuropraxia - focal, segmental demyelination
- axonotomesis - interruption of the axon with no or only partial interruption of the connective tissue framework
- neurotmesis - complete transection
What are the 2 most common clinical signs associated with suprascapular nerve injury? How is it treated?
SWEENEY
- outward bowing/popping of the scapulohumeral joint
- neurogenic atrophy of the supraspinatus and infraspinatus lasting 2-4 weeks
stall rest +/- surgical decompression
What are the 4 most common clinical signs associated with radial nerve injury? How is it treated?
- dropped elbow
- inability to protract limb
- difficulty supporting weight
- denervation atrophy
splinting and stall rest
What 3 diagnostics are used for equine nigropallidal encephalomalacia?
- CSF - high cell count
- MRI
- yellowish malacia in the substancia nigra and extrapyramidal system
What clinical signs are associated with equine leukoencephalomalacia? What does this typically evolve into?
- incoordination, depression
- head pressing
- compulsive walking
- blindness, lack of menace
- liver disease
hyperexcitability, belligerence, agitation, sweating, and delirium
How is equine leukoencephalomalacia diagnosed? Treated?
- history and clinical signs
- elevated liver enzymes and bilirubin
- fumonisin in feed
- postmortem: liquefactive necrosis and degeneration of the white matter
NO TX
What fractures are commonly seen with cranial trauma?
- orbital
- periorbital ring
- zygomatic arch
- mandible and maxillary
- basilar bone** where the rectus capitus pills causes tension
What are the most common causes of spinal cord trauma?
- falls caused by over jumps or rearing backwards
- collision
- osteomyelitis
What clinical signs are associated with Lyme disease?
- chronic weight loss
- sporadic lameness, laminitis, swollen joints
- low-grade fever
- muscle tenderness
- encephaliits
- abortion
