Neurological exam - LA (equine)

Question 1

Approaches - 2

Answer 1

• systematic approach e.g. tests of unconscious proprioception
• anatomic approach - most appropriate for horses/ large animals

Question 2

Distinguish white/ grey matter

Answer 2

WHITE: myelinated axons
GREY: unmyelinated cells and bodies of the axons
- Opposite organisation in brain vs. spinal cord

Question 3

Important aspects of hx to obtain

Answer 3

• did horse look/act clumsy before it was found down?
• any evidence of respiratory dz on property?
• any other horses?
• descriptions of behavioural abnormalities
• client video

Question 4

What does excessive yawning indicate?

Answer 4

forebrain disease (unknown why)

Question 5

What does abnormal behaviour indicate?

Answer 5

= forebrain disease

- e.g. circling, hyperaesthesia, head turn, odd postures

Question 6

What does the cerebellum conrol?

Answer 6

• ascending proprioceptive pathways

- descending motor pathways

Question 7

CS associated with cerebellar dysfunction - 4

Answer 7

• spastic or exaggerated movements
• absence/ diminished menace response
• intention tremor (worse when horse doing something)
• ataxia without weakness

Question 8

Brainstem contents —

Answer 8

• pons and medulla
• reticular formation
• ascending proprioceptive pathways
• descending motor pathways (–> weakness)
• CN nuclei
• when you find dysfunction of these modalities together, think brainstem *

Question 9

What does ataxia, paresis and CN deficits together suggest?

Answer 9

brainstem disease

Question 10

What does a wonky muzzle indicate?

Answer 10

left sided facial nn paralysis

Question 11

Outline PLR

Answer 11

= true reflex

• afferent limb is in optic nn (CN 2)
• efferent is parasumpathetic fibres that run in the oculomotor nn (3) to constrict the pupil
• direct and consensual/ contralateral response. The latter is difficult to assess in horses so as long as you get good direct PLRs in each eye, then don’t worry

Question 12

What does the menace response test?

Answer 12

= requires perception of stimulus

• optic nerve
• optic chiasm
• thalamus
• opposite occipital cortex (but an unconscious event)
• facial nn and nucleus
• (cerebellum)

Question 13

How is vision best tested?

Answer 13

• walk horse around / between obstacles
• fundic exam
• afferent limb of menace response

Question 14

Control of eye position

Answer 14

• oculomotor nn (3)
• trochlear nn (4)
• abducens nn (6)

Question 15

Frequency of strabismus as a CS

Answer 15

uncommon in UK, more common in USA.

Question 16

Method - retractor oculi reflex

Answer 16

= press on cornea through the eyelid, feel for reflex retraction of the globe

• afferent: trigeminal (5) - sensory
• efferent: abducens (6) - motor

Question 17

Lesions in the facial nn (7) are often accompanied by lesions where?

Answer 17

vestibular nn (CN 8) due to anatomical location

Question 18

How do you determine central vs peripheral vestibular disease?

Answer 18

• difficult
• type of nystagmus?
• weakness?
• other CN involved?
• further testing

Question 19

What type of nystagmus does central disease cause?

Answer 19

any type of nystagmus

Question 20

What type of nystagmus does peripheral disease cause?

Answer 20

horizontal nystagmus

Question 21

How does fast phase nystagmus help localise a lesion?

Answer 21

fast phase is away from the site of the lesion

Question 22

What is physiological nystagmus?

Answer 22

changing what you are focusing on

Question 23

How to assess pharyngeal and laryngeal function?

Answer 23

• swallowing
• vocalisation
• slap test (tests intrinsice laryngeal mm function)
• endoscopy *

Question 24

What does eluphenazine toxicity cause? tx?

Answer 24

• causes extrapyrimidal system defects.
• Tx with diphenhydramine
• (n.b. eluphenazine is a drug used to calm horses)

Question 25

Describe Horner's syndrome

Answer 25

= interruption of sympathetic nn pathway between hypothalamus and eye - Ptosis (examine eyelashes closely - normal horse they point out, with horner's they point down) - Miosis - Enopthalmus - Prominent TE - conjunctival and nasal hyperemia - sweating

Question 26

Why do Horner syndrome horses sweat?

Answer 26

when SNS supply to skin is interrupted (this is normally autonomically controlled), horses BVs vasodilate and horses are prone to increased sweat production with vasodilation

Question 27

Why might you get sweating over the mid and caudal neck?

Answer 27

controlled by vertebral nn (C2)

Question 28

Define ataxia

Answer 28

a function deficit associated with defective proprioception

Question 29

CS - ataxia

Answer 29

- hypermetria (exaggerated movements) - hypometria (reduced movements) - dysmetria - truncal sway (back end doesn't follow front end)

Question 30

T/F: assymmetric spinal cord lesions can produce signs similar to certain lamenesses

Answer 30

True

Question 31

What is ataxia generally associated with?

Answer 31

irregular irregularities (i.e. a neurological problem)

Question 32

What is lameness usually associated with?

Answer 32

a regularly irregular problem is usually an orthopaedic problem

Question 33

T/F: bilateral pelvic limb suspensory desmitis and sacroiliac pain are common causes of unusual 'ataxia like' deficint...but usually the deficit is regular

Answer 33

True (despite orthopaedic problems usually tending to be a regularly irregular problem)

Question 34

What are clues that a horse is truly ataxic? 2

Answer 34

- pacing (worse when head lifts up) | - circumduction

Question 35

Possible origins or weakness - 2

Answer 35

systemic or neurological - granulomatous enteritis --> IBD and PLE --> mm wastage - equine motor neuron disease is a neurological problem

Question 36

What type of tail pull is useful to assess a LMN or UMN weakness problem?

Answer 36

- LMN: standing tail pull | - UMN - walking tail pull

Question 37

Features of UMN weakness - 3

Answer 37

- inability to control mm - normal or increased tone - no mm atrophy

Question 38

Features of LMN weakness - 3

Answer 38

- inability to contract the mm - flaccidity - mm atrophy if chronic

Question 39

Examples of lameness caused by mm disease

Answer 39

- post-exercise lameness - exertional rhabdomyolysis (tying up) - polysaccharide storage myopathy - genetic - ischaemic myopathy - uncommon, associated with parasite migration, (aorto-iliac thrombosis) - measure CK and AST

Question 40

Tips for locating spinal lesions

Answer 40

- limb weakness can indicate local SC damage - in a standing horse you can assume that spinal reflexes are intact - most spinal reflexes are hard to assess in adult horses - withdrawal reflexes are useful

Question 41

Sacral and perineal signs

Answer 41

- perineal reflex - sensation - tail flaccidity - rectal exam - urinary incontinence

Question 42

Name some classic cauda equina signs

Answer 42

- impaction in the rectum | - no perineal reflex