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Y4 - Equine > Common equine neurological disease > Flashcards

Common equine neurological disease Flashcards

1
Q

What are different causes of neurological diseases in horses? (viral / Bacterial / parasitic / clostridial toxins / neurodegenerative / metabolic / neurotoxins / vascular)

A
  • Viral = EHV1; rabies; Borna disease; Eastern, Western and Venezuelan encephalitis; West Nile Virus
  • Bacterial = meningitis, encephalitis
  • Protozoal = EPM
  • Parasitic = aberrant migration
  • Clostridial toxins = tetanus, botulism
  • Neurodegenerative disorders = EDM; EMND; EGS; cerebellar abiotrophy
  • Metabolic = HE; intestinal hyperammoniaemia; HYPP, Electrolyte imbalances (Ca, MG, Na…)
  • CVSM
  • Trauma
  • Peripheral nerve pathology = facial paralysis, radial nerve paralysis, sweeney, polyneuritis equi
  • Neurotoxins = Avermectins; Lead, Amitraz, Bracken fern; Leukoencephalomalacia (mouldy corn); raygrass staggers
  • Vascular = Thromboembolic meningoencephalitis
  • Neoplasia
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2
Q

What are syndromes of equine neurological problems?

A
  • Forebrain disease: including seizures and alterations in consciousness
  • Brainstem abnormalities: Cranial nerve abnormalities (facial, vestibular)
  • Horner’s syndrome
  • Urinary incontinence and Cauda Equina Syndrome
  • Spinal cord disease
  • Neuromuscular disease:
    –Abnormal gait: shivering, stringhalt
    –Localised weakness: peripheral nerve injuries
    –Diffuse weakness: EMND, botulism, EGS, HYPP
    –Excessive activity: Tetatus
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3
Q

What is seen with forebrain disease?

A
  • Disorders of behaviour and personality = aggression, compulsive walking, loss of learnt behaviour, yawning…
  • Seizures
  • Blindness
  • Altered states of consciousness:
    -Alert → Quiet → Depressed → Obtunded → Comatose
  • Head posture
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4
Q

What can cause forebrain disease in adults?

A

– Trauma = ↑↑
– Metabolic = HE, intestinal hyperammoniaemia,
– Intracarotid injection
– Cholesterol granuloma
– Infectious meningoencephalomyelitis
– Neoplasia

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5
Q

How would you treat forebrain disease due to trauma in horses?

A
  • Oxygen supplementation
  • Fluid therapy
  • NSAIDs
  • Elevate head
  • Steroids?
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6
Q

What are forebrain diseases due to metabolic disease?

A
  • Hepatic encephalopathy - check liver parameters
  • Intestinal hyperammoniaemia
    -enteritis / /colitis
    -increased permeability
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7
Q

What are forebrain disease due to sleep disorders?

A
  • True narcolepsia = rare
  • Sleep deprivation =
    -inability to lie down
    -muscoskeletal pain
    -fear
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8
Q

What are forebrain disease due to seizures?

A
  • Rare in adults - high seizure threshold
    -trauma, encephalitis, metabolic, neoplasia
  • Neonatal seizures + epilepsy =
    -low seizure threshold
    -most common = PAS, sepsis, trauma
    -also = metabolic juvenile idiopathic arab epilespy (<12m/o)
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9
Q

What are signs of brainstem + cranial nerve disease?

A
  • Vestibular disease = peripheral or central
  • Facial nerve paralysis (VII and VIII frequently affected together)
  • Pharyngeal/laryngeal deficits: dysphagia
  • Other cranial nerve deficits
  • Severe brainstem lesions: gait abnormalities, coma (RAS
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10
Q

What are signs of vestibular disease? What are causes?

A
  • CS =
    -Head tilt
    -Nystagmus
    -Ventral strabismus
    -Ataxia
  • Causes =
    -trauma = central / peripheral
    -idiopathic
    -otitis media / interna
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11
Q

What can cause facial nerve injury? What are CS?

A
  • Causes =
    -Iatrogenic = halters left on during field anaesthesia
    -trauma (+/-vestibular)
    -THO (+/-vestibular)
  • CS =
    -dropped ear
    -ptosis
    -nostril deviation
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12
Q

What can prolonged facial nerve injury lead to?

A
  • Prolonged / permanent deficits =
    -exposure keratitis
    -dysphagia - feed pouching
    -poor performance = nostril collapse
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13
Q

What is horners syndrome? Causes? Signs?

A
  • Interruption of the sympathetic innervation to head + neck
  • Causes = iatrogenic due to extravascular injection of irritant substance (PBZ / buscopan)
  • CS =
    -miosis, enophthalmos, ptosis, protruding nictitating membrane
    -hyperaemic membranes, sweating
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14
Q

What is cauda equina syndrome?

A
  • Sacrococcygeal spinal cord segments, cauda equina, sacral plexus + peripheral nerves to the bladder, rectum, anus, tail + perineum
    -leads to gait abnormalities
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15
Q

What are signs of cauda equina syndrome?

A
  • Degrees of hypotonia, hyporeflexia ad hypalgesia of the tail, anus and perineal region, urinary bladder paralysis, rectal dilation, penile prolapse
  • May also see LMN weakness and paresis of pelvic limbs
  • Can be difficult to distinguish UMN disease with urinary retention and 2ary contusion of tail and anus from recumbency
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16
Q

What are causes of cauda equina syndrome?

A
  • Trauma = sacrococcygeal fracture and luxation, avulsion of the cauda equina
  • Infectious, inflammatory, immune =
    -Inflammatory = polyneuritis equi (± cranial nerve signs)
    -Viral / immune = EHV-1 (± ataxia, ± cranial nerve signs)
    -Verminous = EPM
17
Q

How is EHV-1 myeloencephalopathy diagnosed?

A
  • Lesion location
  • Rule out other causes
  • History of respiratory disease +/or abortion
  • CSF sample = xanthochromic +/-Abs to EHV-1
  • Detection of virus in affected or in-contacts
  • High antibody titres
18
Q

How would you manage EHV-1 myeloencephalopathy?

A
  • Isolate
  • Good prognosis w good nursing
  • Vasculitis = NSAIDS, steroids, aspirin
  • Antivirals = acyclovir, valacyclovir
19
Q

What are causes of spinal cord disease?

A
  • Spinal cord trauma
  • Cervical vertebral malformation (CVM) / Cervical vertebral stenotic myelopathy (CVSM) / Wobbler syndrome
20
Q

What are signs of spinal cord trauma? What is management?

A
  • CS = Vary from ataxia + paresis to recumbency
  • Management =
    -aggressive NSAIDs / steroids
    -surgical tx
    -box rest if standing
    -nursing care if recumbent
    -TIME
21
Q

What is the most common cause of ataxia in horses in the UK? What are the 2 cateogories?

A
  • Cervical vertebral malformation
  • Type I =
    -young horses, dynamic stenosis, at any site
    -compression as result of developmental abnormalities
  • Type II =
    -Older horses, Static stenosis, OA of articular process
    -C5-C6 and C6-C7 most common
22
Q

How can you diagnose CVM?

A
  • Clinical signs
  • Radiography = doesn’t always show abnormalities
  • Myelography - extra information
23
Q

What are risks of myelography?

A
  • Doesn’t always provide extra info
  • Has risks of anaesthesia - induction + recovery of ataxic animal
  • Has risk associated with technique - iatrogenic damage to spine, diffusion of contrast into brain
  • Not performed very often
24
Q

What is management of cervical vertebral malformation?

A
  • Surgery can be performed but it is costly and may only improve the horse on average one grade
  • An ataxic horse should not be ridden
  • Type I = Early detection in young foals and dietary restrictions have resulted in resolution of ataxia and successful careers.
    -Once disease is advanced prognosis is poor
  • Type II = intraarticular corticosteroids (US guided)
25
Q

What are other spinal cord disease?

A
  • Occipitoatlantoaxial malformation
  • Neoplasia
  • Vertebral body osteomyelitis
26
Q

What is seen with neuromuscular disease?

A
  • Abnormal gait = shivering, stringhalt
  • Localised weakness = peripheral nerve injuries
  • Diffuse weakness = EMND, botulism, EGS, HYPP
  • Excess activity = tetanus
27
Q

What is stringhalt?

A
  • Sudden, involuntary, exaggerated flexion of one / both hindlimbs during attempted movement
  • 2 types =
    -australian / plant associated = dandelion, flat weed = Tx = remove from pasture
    -sporadic stringhalt = unknown = Tx = myotenectomy of lateral digital extensor
28
Q

What nerves are commonly affected by peripheral nerve injuries? What is treatment?

A
  • Radial nerve / suprascapular nerve
    -often external blows
  • Tx = antiinflammatories, DMSO, physiotherapy
29
Q

What is equine motor neuron disease?

A
  • Degeneration of motor neurons in spinal cord due to low vit E (and Se?) concentration.
  • Normally history of horse stabled with no access to pasture for a period of time
  • Signs: weight loss (muscle wasting), muscle fasciculations, prolonged recumbency
  • Ocular signs in 30-40% cases: brown pigment accumulation in retina
30
Q

How is equine motor neuron disease diagnosed? Treatment?

A
  • Vit E (+selenium) levels
  • Muscle biopsy
  • Tx = Vit E supplementation
31
Q

What causes botulism? What does it do?

A
  • Clostridium botulinum
    -from contaminated feed (big bales), grass / corn silage
    -water (dead waterfowl)
    -poultry litter + carcasses
  • Blocks ACh release at presynaptic membrane of N-M junction = failure of muscle contraction = weak
    -Flaccid paralysis
32
Q

What are signs of botulism?

A
  • Symmetrical weakness (muscle tremors)
  • Stumble, ataxia
  • Tongue weakness, dysphagia
  • Hang head, nose on ground
  • Dyspnoea - intercostal + diaphragm paralysis
  • GI stasis, urine dribbling
  • SHAKER FOAL SYNDROME
  • Eventually recumbent
33
Q

How is botulism diagnosed / treated? Prognosis?

A
  • Dx = identify toxin / spores
    -stomach content (+/-faces / feed)
  • Tx = antitoxin
    -penicillin
    -supportive, fluids
  • Poor prognosis - if tetraplegia
34
Q

What causes tetanus? What does it do?

A
  • Clostridium tetani
    -gram + anaerobic
    -tetanospasmin =
    neurotoxin = migrates retrograde along motor neurone to spinal cord + brainstem
    -tetanolysin = increase tissue necrosis at site
35
Q

What does tetanospasmin do?

A
  • Inhibits release of glycine
  • Inhibits presynaptic inhibitory neurons in spinal cord
  • Muscles continuously contract
  • Tetany elicited by sound, light, touch
36
Q

What are signs of tetanus?

A

– Elevated tail head
– Stiff gait
– Anxious: ears back, eyelids wide open, nostrils flared, head extended
– Lock jaw: drool, can’t swallow
– Prolapse 3rd eyelid
– Recumbency, rigidity
– Secondary ulcers, trauma

37
Q

How is tetanus treated?

A
  • Support = quiet, dark, low stimulation room. Hydration, deep bedding
  • Eliminate source = open, flush wound. Treat with metronidazole
  • Neutralise unbound toxin = antitoxin
  • Muscle relaxation = acepromazine, diazepam
  • Toxoid = treatment + prevention
38
Q
A

Y4 - Equine (46 decks)

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