26 27 Non-infectious Diseases of the Equine Nervous System 1 and 2

Polyphasic pattern. 3 hrs of slow wave sleep per day standing or recumbent, 20-30 mins of REM sleep in lateral recumbency

What is normal horse sleep like?

Sleep deprivation

This simply refers to a lack of adequate sleep, excessive daytime sleepiness, collapse, and unexplained abrasions of the carpi and fetlocks

Narcolepsy/cataplexy

This refers to a sleep disorder where there is excessive daytime sleepiness with OR without collapse induced by triggers

Narcolepsy, sleep deprivation, cataplexy

Name some things which could be happening in this horse

NSAIDs or imipramine (antidepressant)

How do you treat catalepsy or narcolepsy?

Provocation test (physostigimine)

How do you diagnose narcolepsy?

Seizure

This is a manifestation of abnormal electrical activity of the brain

Generalized and Localized

What are the two different types of seizures

Generalized

This type of seizure is described as tonic/clonic with involuntary recumbency, loss of consciousness, and post ictal blindness and depression

Localized

This type of seizure is more subtle, and may or may not have postictal signs

Intracranial and extracranial

What are the two triggers for seizures in adult horses

Extracranial

Metabolic problems like hepatoencephalopathy, hypocalcemia and uremia are causes of *intracranial* or *extracranial* seizure causes?

Intracranial

Traumatic problems, vascular (strongylus, Intracarotid injection), tumors, and infections (EPM, rabies) are examples of *intracranial* or *extracranial* seizure causes?

Arabs

Which horses mostly need genetic tests to diagnose seizures

Diazepam, Phenobarb, Potassium bromide

How do you treat seizures?

Intracarotid injection

This special cause of a seizure occurs when a drug goes to the brain, happens so acutely the animal seizes "under the needle". Often, the only thing you can do is protect yourself and attempt to calm the reaction with diazepam

Reaction to procaine penicillin

This special cause of a seizure occurs when a specific medication that normally goes IM is accidentally injected into a vessel. The horse has an immediate reaction: spooking, circling, snorting, banging in stall, and eventually seizing where the best you can do is attempt to calm the reaction with diazepam

If water soluble: horse may stand within the hour and be clinically normal in 1-7 days

If oil/insoluble: horse may die

What is the difference between a water soluble drug versus an insoluble/oil based drug being injected intracarotid?

Arabian foal noninfectious diseases

Juvenile Idiopathic Epilepsy, Lavender foal syndrome, OAAM (occipito-atlanto-axial malformation), and cerebellar abiotrophy are all examples of?

a. Juvenile Idiopathic Epilepsy

b. Lavender foal syndrome

d. OAAM (occipito-atlanto-axial malformation)

e. cerebellar abiotrophy

Select the arabian foal noninfectious diseases:

a. Juvenile Idiopathic Epilepsy

b. Lavender foal syndrome

c. Bronchopneumonia

d. OAAM (occipito-atlanto-axial malformation)

e. cerebellar abiotrophy

f. lymphonodular hyperplasia

Juvenile Idiopathic Epilepsy

This autosomal dominant arabian foal disease comes from the egyptian lineage, seen at 2 days to 6 months of age (the foals outgrow it after this).

CAUSES tonic clonic seizures and a normal foal between episodes

FALSE: juvenile idiopathic epilepsy in arabian foals is NOT DEADLY because the animal outgrows it by 6 months AND there is *NO genetic test*

TRUE OR FALSE: Juvenile idiopathic epilepsy in Arabian foals is deadly, but often preventable with a genetic test.

1. Cerebellar abiotrophy = neurologic

2. Lavender foal syndrome = neurologic

3. SCID

4. OAAM (occipitoatlantoaxial malformation) = neurologic

Name the genetic diseases tested for on the Arabian health panel. Which of these are neurologic?

Lavender foal syndrome

This disease causes arabian foals with the recessive genes to be born with a dilute coat color, often brown-purple in color

FALSE: while there IS a genetic test for Lavender foal syndrome, the disease is *FATAL* to foals.

TRUE OR FALSE: Lavender foal syndrome in arabians is often outgrown, though there is a genetic test to diagnose it.

Lavender foal syndrome

This syndrome of arabian foals causes repeated seizures, hyperextension, paddling and IS FATAL

Occipitus (base of skull), Atlas (C1), Axis (C2)

Name the places the malformations occur in in Arabian foals with OAAM

1. Juvenile Idiopathic Epilepsy = dominant

2. Lavender foal syndrome = recessive

3. OAAM (occipito-atlanto-axial malformation) = recessive

4. cerebellar abiotrophy = recessive

Name the dominant and recessive disorders of Arabian foals:

OAAM (occipito-atlanto-axial malformation)

An arabian foal has abnormal head neck carriage, brainstem compression, hyperreflexia, hypertonia, weakness, ataxia in all 4 limbs, and has a click when palpated. He looks like this. Thoughts?

OAAM (occipito-atlanto-axial malformation) in Arabian foal

What is this showing?

Cerebellar abiotrophy

This neurodegeneration in arabian foals occurs AFTER the formation of the cerebellum, showing apoptosis of the Purkinje cells

Cerebellar abiotrophy

An arabian foal presents normal at birth, but at 6 months of age, shows intention head tremor, ataxia such as wide base stance, dysmetria, spasticity, startles easily, and has a lack of menace. Thoughts?

Normal MRI = B

Cerebellar abiotrophy = A

Which of these is normal? What does the abnormal show?

Brain on the left shows a foal with cerebellar abiotrophy, brain on the right is a normal cerebellum

Which of these is normal? What does the abnormal show?

1. Juvenile Idiopathic Epilepsy: onset 2 days-6 mo. = outgrows it

2. Lavender foal syndrome: signs at birth

3. OAAM: signs at birth

4. Cerebellar Abiotrophy: onset 1-6 mo.

What is the difference in onset between all 4 Arabian foal abnormalities?

1. Juvenile Idiopathic Epilepsy: good = grows out of it

2. Lavender foal syndrome: death

3. OAAM: poor

4. Cerebellar Abiotrophy: poor

What is the difference in prognosis between all 4 Arabian foal abnormalities:

Shivers

This is a chronic progressive equine movement disorder of horses that presents with difficulty moving backwards, hyperflexed limbs postures, and tremors during backward movement. The horse may also have a hard time picking up the feet for the farrier

Shivers

What is happening to this horse: showing hyperextension, hyperflexion and abduction, shivering hyperflexion, and shivering forward flexion

Shivers

In horses, what is caused by neuroaxonal degeneration of deep *cerebellar* nuclei

eNAD (equine neuroaxonal dystrophy) and EDM (equine degenerative myeloencephalopathy)

note: these two are not the same thing, but they are two different forms of the same inherited disease in horses

In horses, what problem is caused by an abnormality of neurons in the brainstem and spinal cord?

1. genetic predisposition (signs in first year of life)

2. environmental trigger: lack of vitamin E

What two factors are involved in horses developing eNAD (equine neuroaxonal dystrophy) and EDM (equine degenerative myeloencephalopathy)?

Ataxia with lack of vitamin E

What is the classic description of eNAD (equine neuroaxonal dystrophy) and EDM (equine degenerative myeloencephalopathy)?

Vitamin E deficiency

Heat treated, pelleted feed and horses on dry lots with low quality hay are poster children for WHAT?

eNAD (equine neuroaxonal dystrophy) and EDM (equine degenerative myeloencephalopathy)

A 2 year old horse presents with acute/insidious symmetric ataxia in the pelvic limbs. It has wide based posture, behavior changes, decreased performance, and hypometria. The slap test is decreased and so is cutaneous trunci reflex. You see the horse is in a dry lot and the owner is only giving the horse hay and pelleted feed. After testing the hay, you see it is low quality. Thoughts

Behavior changes, decreased performance, and older than 12 months of age

Name the signs typical of eNAD (equine neuroaxonal dystrophy) and EDM (equine degenerative myeloencephalopathy)?

NO ANTEMORTEM. Diagnosis of exclusion and low vitamin E

How do you diagnose eNAD (equine neuroaxonal dystrophy) and EDM (equine degenerative myeloencephalopathy)?

Vitamin E (water soluble tocopherol).

DO NOT RIDE OR BREED

How do you treat eNAD (equine neuroaxonal dystrophy) and EDM (equine degenerative myeloencephalopathy)? What do you tell the owner?

2 years

How long does it take for a horse to stabilize from eNAD (equine neuroaxonal dystrophy) and EDM (equine degenerative myeloencephalopathy)?

UMN

eNAD (equine neuroaxonal dystrophy) and EDM (equine degenerative myeloencephalopathy) are poster *UMN or LMN* signs

LMN

EMND are poster *UMN or LMN* signs

Cervical vertebral myelopathy

Wobblers, cervical stenotic myelopathy, and cervical vertebral malformation are all the same name for?

Type 1: C1-C6

Type 2: C5-T1

There are two types of CVM (cervical vertebral myelopathy) in horses. Name the difference in location between the two.

Type 1: dynamic compression

Type 2: static compression

There are two types of CVM (cervical vertebral myelopathy) in horses. Name the difference in the types of compression between the two.

Type 1: caused by development

Type 2: caused by degenerative OA

There are two types of CVM (cervical vertebral myelopathy) in horses. Name the difference in cause between the two.

UMN

CVM are poster *UMN or LMN* signs

CVM (cervical vertebral myelopathy)

This disease in horses causes compression of the spinal cord thru stenosis leading to symmetric ataxia, decreased resistance on tail pull, toe dragging, circumduction pelvic limbs, neck pain and UMN paresis in the hind BUT NORMAL mentation

*Large breed fast growing gelding*

Name factors that predispose a horse to cervical vertebral myelopathy

Plain laterolateral radiographs

How do you diagnose CVM (cervical vertebral myelopathy) in horses?

CVM (cervical vertebral myelopathy)

An 8 months old quarter horse colt presents with grade 4/5 ataxia. Thoughts?

CVM (cervical vertebral myelopathy)

A 17 year old thoroughbred gelding presents with a chronic bilateral front limb lameness and a 1 month history of progressive ataxia. Thoughts?

Intravertebral ratio

What ratio gives you an idea of CVM if under 50%?

Positive contrast myelography, CT, MRI

How do you diagnose CVM (cervical vertebral myelopathy)?

CVM (cervical vertebral myelopathy)

What is this?

CVM (cervical vertebral myelopathy) on the right image

Left image is a normal MRI

What is this?

Restrict protein and energy

How should you change the diet when managing a horse with CVM (cervical vertebral myelopathy)?

Ventral interbody vertebral fusion, dorsal laminectomy

What are some examples of surgical treatments for CVM (cervical vertebral myelopathy) in horses?

Cauda equina syndrome

This is a progressive granulomatous polyganglioradiculoneuritis of the cauda equine (infiltration of cytotoxic T cells and macrophages)

note: poly:many, ganglio:group of sensory nerve cells, radiculo:nerve roots that emerge directly from spinal cord, neuritis: peripheral inflammation

Cauda equina syndrome

This refers to the destruction of somatic and autonomic LMN and sensory neurons at the level of the nerve roots and dorsal root ganglion leading to flaccid tail, loss of sensation and perineural area and loss of anal tone in horses

Cauda equina syndrome

A horse presents with dysuria, tail rubbing, flaccid tail, loss of sensation in the perineural area (goes from hyperesthesia to desensitization), and loss of anal tone --> fecal retention and urine overflow. Thoughts?

Must rule out trauma. Will see pleocytosis on CSF, and *high circulating antibodies against P2 myelin* on Electromyelography

How do you diagnose cauda equina syndrome in horses?

Cauda equina syndrome

Which noninfectious neuro disease of horses is diagnosed thru high circulating antibodies against P2 myelin in electromyelography?

Left is a normal cauda equina, right is nodular and firm thickening of multiple nerve roots of the cauda equine

What is this?

Equine motor neurons disease

This is a spontaneous, progressive, sporadic disease of the motor neurons in horses that causes generalized neuromuscular weakness and neurogenic muscle atrophy

Equine Motor Neuron disease (remember EDM, equine degenerative myeloencephalopathy, has this similar pathogenesis, is a differential)

This noninfectious disease in horses occurs due to a lack of antioxidants, where horses in absence of pasture/good quality hay, heat treated pellets, and in a dirt lot are at risk

Equine motor neuron disease

This 9 year old horse horse presents with muscle fasciculations, narrow based stance, and looks better at the walk than standing (he is VERY uncomfortable standing). He does NOT have ataxia. There is muscle wasting of the gluteal and quadriceps muscles and weight loss despite good appetite. Thoughts?

Muscle biopsy of the sacrocaudalis dorsalis medialis (tail elevator muscle)

How do you diagnose equine motor neuron disease?

Equine motor neuron disease

note: this is the tail elevator muscle

Which test in horses do you diagnose using muscle biopsy of the sacrocaudalis dorsalis medialis muscle?

Dietary change and Vitamin E (tocopherol) = prognosis poor for performance, guarded for life

How do you treat equine motor neuron disease? What is the prognosis?

Equine motor neuron disease and eNAD (equine neuroaxonal dystrophy) and EDM (equine degenerative myeloencephalopathy)

The triggering vitamin E insufficiency factor is the same for what two equine noninfectious diseases?

eNAD (equine neuroaxonal dystrophy)/EDM (equine degenerative myeloencephalopathy): younger around 6-24 months

Equine motor neuron disease: middle age, 9 years old and up

Equine motor neuron disease and eNAD (equine neuroaxonal dystrophy)/EDM (equine degenerative myeloencephalopathy) seem very similar. What is the age predilection difference between them?

b. eNAD, EDM

Which has a hereditary basis:

a. Equine motor neuron disease

b. eNAD, EDM

b. eNAD, EDM

Which has UMN signs:

a. Equine motor neuron disease

b. eNAD, EDM

a. Equine motor neuron disease

Which has LMN signs:

a. Equine motor neuron disease

b. eNAD, EDM

b. eNAD, EDM

Which has ataxia and proprioceptive deficits?

a. Equine motor neuron disease

b. eNAD, EDM

a. Equine motor neuron disease

Which has muscle atrophy and fasciculations?

a. Equine motor neuron disease

b. eNAD, EDM

b. eNAD, EDM

Which does NOT have antemortem diagnosis and is strictly by rule out:

a. Equine motor neuron disease

b. eNAD, EDM