Equine Neurology – Flashcards
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What are clinical sign of neurology in horses?
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Ataxia - often due to CP deficits Spasticity (hypometria) - increased ton, stiff awkward movement due to UMN or vestibular dz Hypermetria - uncontrolled rapid forceful movements due to cerebellar dz Weakness
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What does weakness indicate?
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UMN - weakness assoc. with movement, increased tone, hyperreflexic *LMN* - weakness to paralysis, decreased tone, hyporeflexic, *atrophy* Partially denervated muscle - some degree of weakness Completely denervated muscle - flaccid
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How are clinical signs graded?
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Based on severity Grade I: not always perceptible deficit Grade II: always seen but not severe Grade III: severe deficit, sometimes fall Grade IV: severe deficit, frequently fall Grade V: severe deficit, unable to rise
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How do you asses proprioceptive deficits?
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Gait assessment for abnormal foot placement. Increase complexity of movement to execrable proprioceptive signs. Placement testing ot monitor rate of return to normal position.
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What are clinical signs of spinal cord disease proprioceptive deficits?
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Abnormal foot falls -abducted/adducted, stepping on other feet Circumlocution and pivoting Crossing limbs Toe dragging Floating and slapping Standing placement tests (more subjective) Recumbency - difficult to differentiate between CP and weakness
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What are clinical signs of weakness?
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*UMN weakness difficult to detect* *LMN weakness usually assoc. with muscle atrophy*
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How do you assess weakness?
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Tail easily pulled to the side Inability to support weight Exaggerated sitting position on turns and stops Recumbency CP deficits can be confused with weakness if foot is not under center of gravity
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What are clinical signs of spinal cord disease?
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Ataxia due to UMN CP deficits More severe weakness and atrophy due to LMN detectable over time
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What are clinical signs of cerebral disease?
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Depression, obtundation, coma, seizure, circling, compulsive walking, mania, blindness with normal PLRs
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What clinical signs of cranial nerve disease?
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Blindness with abnormal PLRs Strabismus Depression Ataxia
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What CN(s) are affected with head tilt, leaning and circling?
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CN8
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What CN(s) are affected with eyelid or ear droop, facial paresis?
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CN7
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What CN(s) are affected with masseter m. atrophy or paresis?
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CN5
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What CN(s) are affected with dysphagia?
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CN 7 - trouble pretending food CN12 - trouble getting food to back of mouth CN9,10 - swallowing dysfunction
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What multifocal disease is likely with grade III rear limb ataxia, grade I forelimb ataxia, lip/ear/eyelid droop, and gluteal atrophy? Which CN(s) affected?
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EPM CN7 deficits
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What multifocal disease is likely with perineal hypalgesia (lack of anal reflex), head tilt and facial paralysis? Which CN(s) affected?
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Herpes Virus Encephalomyelitis CN7 & 8
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How do you assess *recumbency* in a horse?
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Due to severe ataxia (brain or spinal cord dz) or weakness (*UPM or LMN*) or combination. Reflexes difficult to interpret. Assist to stand for better assessment.
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What is the etiologic agent for *equine leukoencephalomalacia* (ELE)?
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Toxin *Fumonisin* B1 produced by Fusarium moniliforme. "Pink rot" corn. Neuro and hepatic toxicity.
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What do clinical signs appear with ELE?
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Onset 3-4 weeks after ingestion of contaminated feed.
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What is the pathogenesis of ELE?
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Liquefactive cerebral necrosis also involving subcortical white matter affects neurons coming from centers controlling complex functions such as swallowing (predominant cause of death).
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What are clinical signs of ELE?
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Anorexia, depression, toxic mm Inability to swallow Aimless walking, severe agitation Blindness Progresses to recumbency, convulsions, death in hours
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What are lab findings with ELE?
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Increased GGT, SDH, AST Leukopenia with left shift Normal CSF or mononuclear cell pleucytosis
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How do you Dx ELE?
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*Dx based on exclusion of other disease* Post-mortem findings Find Fumonisin B in feed (may be gone already)
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What is the pathogenesis of rabies encephalomyelitis?
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Replicates in muscle at site of bite wound, may remain undetected in myocytes for weeks. Gains access to peripheral nerves, travels to CNS. Incubation weeks to months. Replication within spinal cord neurons. Rapid spread through neurons in CNS to brain.
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What is the most common presents sign in horses with rabies encephalomyelitis?
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Paraparesis due to hind limb bite
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What is the Px for rabies once neuro signs begin?
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Survival short lived, few days to a week
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How do you Dx rabies encephalomyelitis?
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FA testing of brain
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What is the pathogenesis of hepatoencephalopathy?
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Unknown Assoc. with ammonia, aromatic/branched chain AA, dysfunction of GABA receptors, other toxins.
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What are clinical signs of hepatoencephalopathy?
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Cerebral signs: Depression CP deficits Head pressing Blindness Seizures
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What lab test results are consistent with liver disease?
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Increased GGT, AST or SDH
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What lab test results are consistent with liver failure?
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Increased total and direct bilirubin, bile acids
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How do you Tx hepatoencphalopathy?
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Tx liver dz IV glucose Oral branched chain AA to alter ratio Low protein diet Oral antibiotics to reduce colonic ammonia formation and absorption
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How common in equine bacterial meningitis?
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Uncommon in adults and foals
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What are clinical signs of bacterial meningitis? CSF?
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Cerebral disease signs +/- neck stiffness, pain CSF: high neutrophil and protein
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How do you Tx bacterial meningitis? Px?
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IV antimicrobials broad spec (E. coli and Strep) Px guarded to poor (residual deficits)
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What are clinical signs of a brain abscess? Which bacterial is implicated?
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Cerebral disease signs Not painful Often unilateral Streptococcus equi equi
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How do you Dx brain abscess?
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CSF: high protein and cell count CT or MRI
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How do you Tx brain abscess? Px?
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Antimicrobial therapy Px guarded (residual deficits)
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What is the etiology of Equine Protozoal Myelitis (EPM)?
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Sarcocycstic neurona Opposum parasite, infection results from ingestion of feed contaminated with opossum feces. Horse dead-end host.
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What is the pathogenesis of EPM?
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Sarcocystis neurona sporozoites enter horse via intestinal tract. Access circulation and enter vascular endothelial cells. Disease when organism accesses CNS (<1% horses exposed).
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What lesions does EPM cause?
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Multifocal necrosis of CNS. Usually slowly progressive over a period of weeks.
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What are clinical signs of EPM?
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Vague lameness Asymmetrical signs common Spinal cord disease signs: UMN CP deficits, LMN weakness and atrophy Brain stem disease signs <1% have cerebral signs
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How do you Dx EPM?
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*No definitive test, R/O other DDx* CNS clinical signs CSF and serum antibody test: negative R/O, positive indicates exposure Immunologic testing to confirm exposure to S. neurona - *IFAT* most sensitive/specific (WB, SAG-1 ELISA not as good)
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How do you Tx EPM?
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Antiprotozoals Antiinflammatories
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Which antiprotozoals are approved to Tx EPM?
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Sulfadiazine & Pyrimethamine - SE: anemia, neutropenia, thrombocytopenia, abortion Ponazuril (Marquis) or toltrazuril - few SE, increased bioavailability with DMSO PO Nitazoxanide (Navigator) - taken off market, SE: GI Diclazuril pellers
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What antiinflammatories are used to Tx EPM?
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DMSO, glucocorticoids, NSAIDs
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What is the Px for EPM?
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70-80% respond to Tx with some improvement Only 25-50% return to previous function
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Is there a vaccine for EPM?
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Yes, USDA approved but no efficacy studies and not considered effective by most. Affect testing.
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What is verminous myeloencephalitis?
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Aberrant migration of multiple parasites (Halicephalobus, Strongylus, Draschia, Setaria, Hypoderma etc)
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What are clinical signs of verminous myeloencephalitits? CSF?
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Neuro signs can affect any portion of brain/spinal cord. CSF: norma or eosinophilic or mononuclear cell inflammation
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Which parasite is most common with verminous myeloencephalitis in horses? What other organs does it affect?
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*Halicephalobus deletrix* Saprophytic nematode *ingested via nasal/oral mucosa and spreads hematogenously*. Affects *kidneys*, heart, lungs, stomach, bones
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How do you Tx verminous myeloencephalitis? Px?
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Anthelminitics: Fenbendazole, Diethyl carbamezine or ivermectin for nematodes, Organophosphates for hypoderma Antiinflammatories: phenybutazone, flunixin, DMSO Px poorm no successful tx reported
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What neural neoplasias are seen in horses?
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Rare in horses, esp. 1º Lymphosarcoma, melanoma, hemangiosarcoma
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What are clinical signs of neural neoplasia? CSF?
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Often unilateral signs Severity may wax/wane CSF: elevated protein with normal cells +/- xanthochromia
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What is a cholesteatoma?
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Idiopathic cholesterol granuloma of choroid plexus, occurs in 15-20% of old horses. Circumscribed firm white "rocks."
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What are clinical signs of cholesteatoma? CSF?
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Most clinically silent unless large enough to cause compression. Intermittent signs, depression progressing to obtundation and coma. CSF: elevated protein and xanthrochromia
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What is the etiology of cervical vertebral malformation? Signalment?
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Unknown. Osteochondrosis suspected, genetic link not proven, assoc with diet (copper deficiency, protein or CHO excess). Occurs in any breed/age esp. young rapidly growing animals?
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What are the 2 forms of cervical vertebral malformation?
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1. Cervical vertebral instability 2. Cervical static stenosis
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What is the cause of cervical vertebral *instability*?
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Deformation of vertebral bodies, malarticulation, and subluxation on flexion causes dynamic compression. Deformation from abnormal endochondral ossification of the caudal physis. Short vertebral body compared to dorsal lamina.
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What is the cause of cervical static *stenosis*?
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DJD of the articular facets with bone and soft tissue impingement into the vertebral canal initiated by aberrations in cartilage maturation.
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What are clinical signs of cervical vertebral malformation?
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Ataxia of rear limbs, usually one grade less involvement of front limbs. CP deficits with circumbduction (ataxia), sometimes weakness.
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How do you *Dx cervical vertebral malformation*?
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*Myelography only way to confirm Dx* Take plain rads first to R/O DDx May show reduced spinal cord dimensions, ski slopes. CSF normal
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How do you Tx cervical vertebral malformation?
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Surgical stabilization Mild cases - anti-inflammatories, diety restriction, copper supplementation Severe cases - euthanasia
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What is the most common cause of spinal cord signs in foals 6 mo - 1 yo?
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Spinal abscess
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What is the etiology of spinal abscess?
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*Hematogenous spread* of infection from other disease, esp. pneumonia, foot abscesses.
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How do you Dx spinal abscess?
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CSF: neutrophilic inflammation Increased fibrinogen and neutrophils in peripheral blood
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How do you Tx spinal abscess? Px?
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Antimicrobials for E. coli and Strep. zooepidemicus or S. equi. Sometimes residual deficits prevent athleticism.
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Whenever trauma-induced nervous system signs are seen, what should also be suspected?
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Always suspect pre-existing nervous system signs that led to fall.
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What are signs of CNS trauma? Px?
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Acute onset of signs due to edema or hemorrhage. Improvement may continue over several weeks if hemorrhage. Px guarded
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What is syndrome of CNS trauma resulting in blindness?
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Frequently starting gate injuries or stallions "throwing" their heads. Bright and alert habitus, dilated pupils, optic nerve trauma assoc. with contracoup. Blindness usually permanent.
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What are signs of vestibular disease in horses?
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Head tilt (ventral deviation of poll) Nystagmus Falling, reluctant to walk Extensor or contralateral extensor hypotonia Circling when forced to walk Lies on or leans against wall toward affected side Body flexed with concavity
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If CN7 & 8 deficits are present along with other neuro deficits what type of vestibular disease is likely?
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Test for central dz first
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If only CN7 & 8 deficits are present with no other neuro signs, what type of vestibular disease is likely?
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Must consider both peripheral and central dz
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If only CN7 deficits are present with no other neuro signs, what type of vestibular disease is likely?
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Peripheral dz
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What are clinical signs of *peripheral vestibular disease*?
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Asymmetric ataxia Maintains strength Only VII deficits Horizontal nystagmus No depression
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What are clinical signs of *central vestibular disease*?
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Generalized CP deficits Weakness Other cranial nerve deficits Horizontal or vertical nystagmus May have depression
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What are causes of peripheral vestibular disease in horses?
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Trauma Guttural Pouch Disease Otitis media-interna Temporohyoid OA
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What are causes of trauma resulting in peripheral vestibular dz? Tx?
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Horses in starting gait or training to tie hit top of gate or trailer or rear up and flip over backwards. Trauma to poll. Stress fracture of basisphenoid. Tx: antiinflammatoeis
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What is the etiology of inner ear disease in horses?
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Streptococcus zooepidemicus Staphylococcus E. coli Actinobacillus
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What is the pathogenesis of inner ear disease in horses?
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Respiratory infection of trauma. Ascending infection from guttural pouch or hematogenous spread.
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How do you Dx inner ear dz?
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Tympanocentesis culture
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How do you Tx inner ear disease?
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Antinflammatories Antimicrobials: Ceftiofur, Penicillin gentamicin, Chloramphenicol, Enrofloxacin
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What is the pathogenesis of temporohyoid osteoarthropathy?
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Inflammation induces bony proliferation at articulation of the stylohyoid bone with the petrous portion of the temporal bone. Fusion of temporohyoid joint - reduced mobility, stress fracture risk.
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What are clinical signs of temporohyoid osteoarthropathy?
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Head tossing Reluctance to flexion during riding CN7 & 8 deficits: ear/eye/lip droop, head tilt, leaning, loss of balance
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How do you Dx temporohyoid osteoarthropathy?
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Endoscopy Radiographs/CT
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How do you medically Tx temporohyoid osteoarthropathy?
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Antiinflammatories and antimicrobials (2º bacterial infection)
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How do you Sx Tx temporohyoid osteoarthropathy?
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Partial stylohyoid ostectomy Certohyoidectomy
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What is the Px for temporohyoid osteoarthropathy?
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Px guarded to poor for complete resolution of deficits. Sx complications - persistence or worsening of deficits
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What are causes of central vestibular disease in horses?
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EPM Herpes West Nile Viral Encephalomyelitis Brain Abscess Verminous encephalitis Trauma
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How do you Tx central vestibular disease?
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Antiinflammatories Antiprotozoals Antimicrobials (abscess) Anthelmintics (ivermectin, high doses of fenbendazole)
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What is the signalment for idiopathic epilepsy?
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Arabian foals Uncommon in horses, rare in adults.
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How do you Tx idiopathic epilepsy?
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Long term control sometimes rewarding with phenobarb, phenytoin. Arabian foals "outgrow" the syndrome. Euthanasia often necessary due to danger.
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What is Polyneuritis equi (Cauda equina neuritis)? Dx?
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Idiopathic disease Definitive Dx not possible
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What are clinical signs for *polyneuritis equi* (Cauda equina neuritis)?
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Perineal hyperesthesia and tail rubbing, progresses to hypoesthesia and paralysis of perineum. Eventually paralysis of bladder, fecal retention, *paralysis of tail*. Can progress to paralysis and muscle atrophy of gluteals. +/- Brain stem signs
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What is the etiology of *Equine Degenerative Myeloencephalopathy*?
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Etiology unkown Related to *Vitamin E deficiency* and familial predisposition.
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What are clinical signs of Equine Degenerative Myeloencephalopathy?
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Age of onset usually 6-18 months. CP deficits +/- weakness Ascending signs +/- brain stem signs
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What are equine neuromuscular diseases?
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Tetanus
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What is the pathogenesis of tetanus?
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Muscle spasm due to loss of inhibitory neurotransmitter in spinal cord and brainstem. Increased extensor tone and spasm
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What are clinical signs of tetanus?
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Generalized signs Recumbency with increased extensor tone, stiff neck, lockjaw, prolapsed third eyelid, opisthotonus, stiff tail and ears, hyperesthesia.
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How do you Tx tetanus?
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Nursing care Tetanus antitoxin (IM or in CSF) Penicillin
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What is *tetanus prophylaxis* for horses?
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Active immunization with tetanus *toxoid* - 2 shot series. Single booster in *previously vaccinated horse*. Booster pregnanct mares in last 30 days gestation to avoid TAT administration in foals. Tetanus *antitoxin to previously unvaccinated horse*s with wound.
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What is the Px for tetanus?
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Horses most suscpetible species, high mortality.
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What is "Shaker Foal Syndrome"?
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Botulism - flaccid tetraparesis
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What are sources of botulism?
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C. botulinum type B - soil in Kentucky and Atlantic seaboard C. botulinum type C - round focal source anywhere (bale of hay, lawn clippings) Wound botulism
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What are clinical signs of botulism?
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First signs = hanging head Difficult eating Generalized weakness Decreased eyelid, tail, tongue tone
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How do you Dx botulism?
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Clinical signs EMG Assay toxin in feces (UPenn)
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How do you Tx botulism?
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Supportive care Penicillin Antitoxin $$$
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What is Equine Motor Neuron Disease (EMND)?
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Neuronal degeneration of ventral spinal cord. Regional disease, multifactorial.
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What are clinical signs of EMND?
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Slowly progressive weakness, muscle wasting.
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How do you Dx and Tx EMND? Px?
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Dx: EMG, coccygeal nerve histopath No Tx, Poor Px
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What is Stringhalt and Shivering? What plants are associated?
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Exaggerated flexion of the hock of one or more rear limbs. Neuropathy, myopathy or spinal cord dz. Shivers (in draft breeds esp. upon backing). Plants - Hypochaeris, Lathyrus
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How do you Tx Stringhalt and Shivering?
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No Tx Sx tenectomy of lateral digital extensor tendon? May spontaneously resolve
