Large animal neurological conditions Flashcards
Name three spinal cord diseases in equines
Cervical vertebral stenosis myelopathy
Equine Herpes Virus
Occipito-atlantoaxial malformation
Name four peripheral nerve diseases in equines
Stringhalt
Shivers
Head shaking
Horner’s syndrome
What are the three types of ataxia?
- Proprioceptive - abnormal limb placement,limb paresis, weakness
- Vestibular - Head tilt, rolling/falling to one side
- Cerebellar - wide base stance, intention tremors
Define paresis
Reduction in voluntary movement
Define monoparesis
affecting one limb
Define hemiparesis
affecting both limbs on the same side of the body
Define paraparesis
Affecting either both forelimbs or both hindlimbs
Define tetraparesis
Affecting all four limbs
Name three diseases affecting the spinal cord
Cervical vertebral stenotic myelopathy
Equine Herpes Virus
Occipito-atlantoaxial malformation
Describe cervical vertebral stenotic myelopathy
Cervical vertebral malformation
‘Wobblers’ syndrome – care with use of this term
Compression of the cervical spinal cord due to changes in the vertebral column
Males > females
Type I and II
Describe type I CVSM
Younger horses – Thoroughbred, Warmblood
Compression due to excess movement of the vertebrae
Dynamic
Normally affects C3-C5
Causes:
Genetics
Nutrition
Rapid growth
Trauma
Describe type II CVSM
Older horses
Due to arthritic changes on articular process joints
Traumatic
Acquired
Normally affects C5-7
What are the clinical signs of cervical vertebral stenotic myelopathy?
Progressive then plateau (unless traumatic)
Hindlimb ataxia +/- forelimb dysmetria
Dragging of the toes
Wide based stance
‘Sway’ at walk
Neck pain/stiffness (C2-4)
Circumduct hindlimbs when circling
All made worse by neck flexion
What are the 6 stages of the mayhew ataxia grading system?
0- no neurological deficits
1 - Neurological deficits just detected at walk. Worsened by turning, backing or extension of the neck
2 - Neurological deficits easily detected at walk. Exaggerated by turning, backing or extension of the neck
3 - Neurological deficits prominent at walk with a tendency to buckle or fall when turned, backed or neck extended
4 - Stumbling, tripping and falling at walk
5 - Recumbent
How would you diagnose CVSM?
Clinical signs
Radiography
Measure canal to vertebra ratio
Myelography
CT?
Difficult to get lower neck.
How would you medically treat CVSM?
Anti-inflammatories
Box rest
Type 1:
Reduced carbohydrate and protein
Vit E and selenium for nervous system health
Type II:
Glucocorticoid injection into the joint
How would you surgically treat CVSM?
Very specialist surgery – only a handful of surgeons in the UK
Rarely carried out as most horses still unsafe to ride
Fusion of the vertebrae:
Bagby basket technique
Kerf Cut Cylinder
Locking compression plate
Describe the equine herpes virus (EHV-1)
Many strains of Equine Herpes Virus – 1, 3, 4
1 – most common to cause neuro disease
4 – occasionally causes neuro disease
Causes inflammation of the blood vessels ‘vasculitis’ ischaemia
INFECTIOUS – air-borne virus
How can equine herpes virus present?
Respiratory disease
Abortion
Neonatal disease
Thought to be infected within weeks of birth
Incubates for 2-10 days but can cause latent infection – lymph nodes
How do you diagnose EHV-1?
CSF sample
Virus isolation
Antibodies
Post mortem
Histopathology
How do you treat EHV-1?
Supportive treatment
Many horses will stabilise rapidly and improve over
a few days
Deep bedding
Sling or scoop if recumbent
Urinary catheterisation
+/- anti-viral medication
+/- glucocorticoids
Full recovery can take up to 18 months.
Describe management of a EHV-1 outbreak
Isolate horse as soon as disease suspected - barrier nurse
No movement of horses on or off the yard for at least 3 weeks after last case identified
Burn infected bedding
Disinfect stable, equipment and clothing
Vaccination provides only partial and short-lived immunity
Not appropriate to vaccinate at-risk animals during a breakout
What is occipito-atlantoaxial malformation?
Malformation of the vertebra in cranial cervical spine
Compresses spinal cord
Arab breeds
Typically effects from birth 1 year of age
What are the clinical signs of occipito-atlantoaxial malformation?
Crepitus on movement of the neck
Left or right bony prominence
Scoliosis
Tetraplegia
How do you treat occipito-atlantoaxial malformation?
Management or euthanasia
Describe stringhalt
Motor disorder of unknown aetiology
Involuntary hyperflexion of hock whilst moving
Types
Idiopathic
Epidemic / ‘Australian stringhalt’ - ?dandelion / ?flatweed.
Intoxication – sweet pea plants
What are the clinical signs of stringhalt?
Can be unilateral or bilateral
Worse when backing up
Grade 1 – only mild signs noted when animal starts to move
to
Grade V – reluctant to move and ‘bunny hops’
How do you diagnose stringhalt?
Diagnosis is based on clinical signs and ruling out other diseases.
How do you treat stringhalt?
Remove toxins
Tenotomy or tenectomy of the lateral digital extensor tendon
Phenytoin (muscle relaxant)
Describe radial nerve damage
Provides innervation to the extensor muscles of the forelimb
Causes extensor paresis
Can be seen following:
Lateral recumbency during GA
Kick injury
What are the clinical signs of radial nerve damage?
Location of injury can alter clinical signs
Near the elbow joint ‘high’
Dropped elbow
Toe scuffing
Distal injury ‘low’
Knuckling of carpus, fetlock and pastern joints
Over time leads to atrophy of the extensor muscles`
Describe femoral nerve damage
Has motor and sensory functions
saphenous branch
Most commonly occurs due to extended HL position during GA
Leads to:
Loss of weight support
Inability to extend or fix stifle
Sensory deficit to medial thigh
Describe sciatic nerve damage
Uncommon
Mostly caused by poor injection technique
Limb often dropped with stifle dropped and extended
Commonly seen in post-partum cow
Describe treatment of peripheral nerve injuries
Can take weeks months to recover
Anti-inflammatories
Support limb
Bandages
Splints
Support the horse if required (slings)
Aim to slow down muscle atrophy
Passive movement
Regular stimulation
Deep, comfortable bedding
IVFT
Sedation if distressed
Describe idiopathic head shaking
‘Abnormal condition when a horse shakes it’s head in the absence of obvious external stimuli’ Mair (2013)
Unknown aetiology
? trigeminal neuritis
? photophobia
Seasonal variation – late spring/summer
What are the clinical signs of idiopathic head shaking?
Most commonly occur during ridden exercise
Rapid vertical head flicking
Sneeze/snort at walk or trot
‘Nudging’ owner at walk
?Engorgement of superficial facial vessels
How do you diagnose idiopathic head shaking?
Extensive – rule out all other causes
Ears
Eyes
Cervical spine
Respiratory
CNS
Teeth
Oral cavity
Can block infra-orbital nerve
How do you treat idiopathic head shaking?
Unlikely to be effective – inconsistent results
Nose nets can be used short term
Steroids (inhaled or systemic)
Anti-histamines
Bilateral infra-orbital neurectomy
Coils
PENS – percutaneous electrical nerve stimulation
Describe horner’s syndrome
Loss of sympathetic innervation to the head
Damage to vagosympathetic trunk as it runs through the neck
Clinical signs
Drooping of the eyelid (ptosis)
Retraction of the eye (enophthalamus) protrusion of third eyelid
Mild dilation of the pupil (mydriasis)
Inappropriate facial sweating
Describe downer cows
Cow has been down for more than 24 hours
Usually related to calving
Approx ½ develop within 24 hours after calving.
If they are in the same position >6hrs then leads to secondary pressure damage, compartment syndrome etc
What are the types of downer cows?
‘Alert downer’ – no sign of systemic disease
‘Non-alert downer’ – systemic illness
‘Creepers’ / ‘crawlers’ – cows that can attempt to rise and can move themselves around
Name possible causes of downer cows
Mineral deficiency
Dystocia
Fractures
Luxations / subluxations
Muscle damage
Nerve damage
Toxaemia – toxins in the blood stream
Describe treatment of downer cows
Treat underlying cause
Supportive care
Comfortable, clean, non-slip bedding
Provision of food / water
Turning cow every 3 hours
Anti-inflammatories
Assist to rise
Diagnosis
Improve blood supply
What lifting aids can be used for downer cows?
Hip clamp / Bagshaw hoist
inflatable bags
slings
What is the prognosis of downer cows?
Approximately half of all downer cows will get up in 4-7 days.
If the cow has been down for longer than 10 days, prognosis is poor.
Describe spastic paresis
Elso heel’
Asymmetric spasticity and excess extensor tone in hindlimb(s)
Gastrocnemius
Superficial digital flexor tendon
Normal when recumbent
Aetiology unknown – ?genetic
What are the clinical signs of spastic paresis?
Seen in most breeds
Young animals - 3 weeks 1 year
Progressive
Unable to flex hock
Circumducts affected limb
How do you manage spastic paresis?
Aim to usually to provide sufficient relief to finish for slaughter
Neurectomy of the tibial nerve rootlets supplying the gastrocnemius
Tenotomy of the gastrocnemius tendon
Partial tenectomy of the two insertions gastrocnemius and calcanean tendon
Describe obturator nerve paralysis
Motor innervation to adductor muscles of the limb
Well protected in the horse and small ruminants
Seen in cows during dystocia
What are the clinical signs of obturator nerve paralysis?
Non-slip surface minimal deficits seen
Slippery surface splayed legs
May ‘bunny hop’ when moving
Treatment is the same as horses
Hobbles used
Define spinal abscesses
Often originate from:
Pre-existing osteomyelitis
Haematogenous spread from heart, lung, injection site etc
If remains within vertebral body myelopathy
If vertebrae fractures spinal trauma
If erodes through dura mata septic meningitis
Treatment is supportive and aggressive antibacterial therapy
Describe tetanus
Equine and farm animals
Clostridium tetani spores found in soil
Release 2 toxins
Contaminate soft tissue injuries
Causes contraction and spasm of muscles
Stiff gait recumbency with rigidity of neck and limbs
Describe treatment of tetanus
Treatment
Sedation/muscle relaxants
Anti-toxin
Fluid/nutritional support
Deep bedding
If they can still drink – good prognosis
If recumbent – grave prognosis
Vaccination!
Describe botulism
Clostridium botulinum
‘Foraged’ – silage
Clinical signs tend to be acute:
Flaccidity
Weakness
Trembling
Drooling
Recumbency
Sudden death
What is the treatment for botulism?
Anti-toxin
Antibiotics Deep bedding Nursing and nutritional support
