Equine Neurology Flashcards
How do horses with CNS disorders often present?
–Ataxia
–Seizures/collapse
–Blindness
–Autonomic dysfunction (bladder, GIT, other)
What are the common disorders of peripheral nervous system (2)
–Weakness
–Autonomic dysfunction (dysphagia, bladder, GIT)
What is the most common and important CNS disease in the UK?
Ataxia caused by cervical vertebral disease
What is tthe most clinically important (and relatively UK specific) neurological disease of the peripheral nervous system in the UK?
Equine grass sickness
What are the 2 degnerative central causes of neuro disease?
•Cervical Vertebral Malformation
–Type 1: Juvenile onset
–Type 2: Adult onset osteoarthritis
•Equine Degenerative Myeloencephalopathy
Name 2 anomalous Central causes of Neurological Disease (5)
- Benign epilepsy of Arabian foals
- Narcolepsy
- Hydrocephalus
- Occipitoatlantal malformations
- Cerebellar Abiotrophy
What should you not do in benign epilepsy of arabian foals?
Euthanse - they grow out of it
Name 2 metabolic Central causes of Neurological Disease (4)
- Hepatic encephalopathy
- Perinatal asphyxia syndrome
- Hypoglycaemia
- Electrolyte abnormalities
Name a nutritional Central causes of Neurological Disease
•Equine Degenerative Myeloencephelapoathy
A) Name a common neoplastic Central causes of Neurological Disease
B) Name 2 rare (3)
A)
•Pituitary Pars Intermedia Dysfunction
B)
–Hamartoma
–Cholesterinic granuloma
–Epidural lymphosarcoma
Name infectious central causes of neuro disease:
A) Bacterial
B) Viral (4)
C) Spirochete
D) Other
A) Bacterial meningitis (foals), Abcessation
B) Equine Herpes Virus
- *Togaviridae (Eastern, Western and Venuzuelan equine encephalitis)
- *Flavivirus (West Nile Virus, Japanese encephalitis)
- *Hendra virus, Borna, Rabies
C) Borrelia Burgdoferri
D) Equine Protozoal Myeloencehpalitis
Name an inflammatory Central cause of Neurological Disease
•Polyneuritis equi
–Cranial nerves and cauda equiina
Name 2 idiopathic central casues of neuro disease (4)
- Idiopathic hypersomnia
- Idiopathic epilepsy
- Narcolepsy
- Idiopathic headshaking
Name 3 toxic Central causes of Neurological Disease (5)
- Rye Grass Staggers
- (Lead – more in cattle)
- Ivermectin/Moxidectin
–Usualy lipid bound but a lack of body fat means you can over dose
- Fluphenazine
- *Yellow star thistle
Name a vascular Central causes of Neurological Disease
•Postanaesthetic myelopathy
Define ataxia
•Lack of order, inconsistency
What is the grading of ataxia?
–Grade 0: Normal
–Grade 1: Minimal deficits noted, requires provocative testing to identify
–Grade 2: Mild abnormality seen at walk
–Grade 3: Easy to see at walk
–Grade 4: Very ataxic, may fall with provacative testing (circling)
–Grade 5: Recumbent (cannot stand)
What is wobblers syndrome?
Cervical vertebral malformation (CVM)
What are the 2 types of CVM and where do they occur?
–Type 1: Juvenille onset (C3-5 compression)
- They might not present until 5 yo! As they were not worked
- Fast growing
- Common in yearlings/2 yo
–Type 2: Mature onset
A) Which breed is at risk of CVM?
B) Which gender?
A) Thoroughbred/ WB
B) Male
What are the 2 presentations of CVM and which one is ataxic at all times?
- Functional (dynamic)
- Absolute (static)
–Ataxic at all times
What are the clinical signs of CVM?
Include which limbs are worse and why
–Bilateral ataxia
•Hindlimbs worse than forelimbs
»Spinocerebellar tracts supply HL Sit superficial so more llikely to be affected by compression
- Flexor weakness (toe dragging)
- Extensor weakness (walking tail pull - UMN)
–Dysmetria ( lack of coordination) and spasticity
–Onset
•Usually gradual, may fluctuate with acute exacerbation
When are FL the same or worse than HL in CVM?
C5-T1 lesion
What are the 3 predispositions to type 1 CVM
•Affects young animals
–Less than 2 years of age
–Complex of developmental orthopaedic disease
•Nutritional
–High energy and protein
- Never seen in wild equidae
- Genetic
What is type 2 CVM in older horses?
Where is it typically seen in the horse?
–Osteoarthritis of cervical articular articulations
•Typically C5, C6, C
How can we diagnose CVM?
–Plain radiographs
- Stenosis, OA
- Minimal Saggital Diameter and sagittal ratios
–Suggestive of CVM
–Myelography
- Required if contemplating surgery
- Premortem confirmation
–Otherwise of little value
How do you calculate saggitial ratios?
•Divide the width of the spinal canal by the width of the corresponding vertebral body at the cranial aspect of the widest point
What does it mean if the saggital ratio is <50% ?
There is an 80% chance that a compressive lesion will be observed on a myelogram
What does it mean If the saggital ratio is > 50%?
then there is a 20% chance that the horse is a “Wobbler”
How do you definitively diagnose CVM? How is it done?
Myelogram:
–General anesthesia
–Plain radiographs
–Inject radiographic contrast media into intrathecal space (NOT epidural)
–Radiographs in neutral, flexion, extension
–Minimum 12 films
What is seen on CSF with CVM?
Normal
What is occasionally seen on EMG with CVM?
Cervical denervation
What are the 3 sites for CSF and which is the common one?
–Common site: Caudal at LS space
–Alantico occitpial
–Atlanto axial joint
How can we manage CVM? Indicate which is best in each type
- Intra-articular glucocorticoids common in type 2
- Exercise and nutritional restriction
–Help stabilize cases and occasional improvement in type 1 disease
•Surgical stabilisation
Name 4 factors to consider prior to surgery (7)
- Duration of ataxia
- Age of horse
- Severity
- Co-existing conditions
- Intended use
- Owner commitment
- Sites affected (complete myelographic study) & dynamic vs static
How does CVM surgery work?
- Allows fusion of vertebra over time
- Fusion resolves vertebral instability
- Bone remodeling
- Prevents spinal cord
Compression
•Gradual improvement
in neurologic function
A) What condition looks similar to CVM?
B) What signs are seen?
A)
•Equine Degenerative Myeloencephalopathy (EDM)
B)
- Symmetric tetraparesis and ataxia
- Worse in rear limbs
- Hyporeflexia
A) What horses does EDM affect?
B) How do we diagnose?
A) Young
B)
–CSF, blood, spinal radiographs and EMG normal
–Euthanise –confirm at PM
What is the pathophysiology of EDM?
•Neuroaxonal dystrophy
–Spinal cord (cervical)
–Brain stem sensory and proprioceptive nuclei
•Fibre degeneration
–Ascending and descending pathways
•Vit E/Se deficiency
–Antioxidants
What is seen on necropsy of an EDM horse?
•No gross lesions
–Neuroaxonal degeneration of brain stem, cervical and especially in thoracic and lumber spinal cord
What is the cause of EDM?
Unknown
How can you treat EDM?
–Generally valueless
–High doses of vit. E occasionally useful
–Not curative
How do you prevent EDM?
–Decrease incidence in siblings or on farms with history of disease
–Vit. E daily for 2 years
What are the signs of EHV 1?
- Abortion, stillbirth, weak foals
- Respiratory disease
–Neurological disease – Myeloencephalopathy
What disease do you get with EHV 4?
•Upper respiratory tract disease
–Abortion
–(? Myeloencephalopathy)
A) How are EHV 1 cases seen?
B) What signs are shown?
A) Sporadic
B)
–Other horses affected
•Oedema (scrotal, distal limb), pyrexia, respiratory
–Hind limb ataxia – symmetrical
•Urinary bladder paralysis (dribbling urine)
–Sacrococcygeal spinal cord
–May progressively ascend the CNS
–Decreased tail tone