13. Neuromuscular Disorders and Peripheral Myelopathies

Question 1

What is the etiology of Botulism? What kind of bacteria is it? Where is it normally found?

Answer 1

Gram positive, spore forming, anaerobic bacillus
-Normal in soil
-Eight toxins (A-G)
-B most common

Question 2

What is the pathophysiology of Botulism? What is affected and what signs does that cause?

Answer 2

-Toxin prevent release of ACH at neuromuscular junction (no smooth muscle contraction)
-Flaccid Paralysis

Question 3

How do horses get botulism?

Answer 3

Ingestion of pre-formed toxin
-Silage, feed with carcass, rotten or spoiled feed, spoiled round bale, poultry litter
-Growth of organism in a wound
-Organism in GIT (foal)
(think anaerobic conditions)

Question 4

What is the most common presentation of botulism in foals?

Answer 4

Toxicoinfectious
-1-2 months
-rapid onset
-stumble, weak, dragging toes
-Recumbency
-dehydrated and hypoglycemic
-prognosis good intensive care

Question 5

What type of intensive care do foals need if they have Botulism?

Answer 5

Oxygen and ventilator

Question 6

What are some clinical signs of botulism in horses?

Answer 6

Dysphagia - decreased tongue tone
Lowered head, dul
Weak, shuffling gate, dragging toes
Decerased PLR
Weak tail and anal tone
Ileus - present for colic
Recumbency (60-90% mortality)

Question 7

Is Botulism a straightforward diagnosis?

Answer 7

No, may not be thinking it until multiple horses have it and you ask the right history questions

Question 8

How do you diagnose Botulism?

Answer 8

Clinical signs - tongue, weakness, gait
Grain test - normal horse eat 250ml sweet feed in <2 min (Infected = hard to swallow/drop grain)
Toxin detection in GI content, feces, wound (mouse, PCR)
Post-mortem exam

Question 9

How do you treat Botulism?

Answer 9

Botulism antitoxin - plasma from hyperimmunixed horse, antibodies, only bind circulating
Supportive care

Question 10

What kind of supportive care can you provide for botulism?

Answer 10

Nutritional and Fluid - cant eat or drink
Oxygen - cant breath
Urinary Catheter - cant urinate
Ocular care - cant blink
Wound Management - cant stand
Antibiotics?

Question 11

How long may you need to provide this supportive care?

Answer 11

Can be greater than 2 weeks for the end plate to regenerate ACH receptors

Question 12

Do Botulism horses recover?

Answer 12

Yes, quite well if you take the time and support

Question 13

Can you prevent Botulism?

Answer 13

Vaccination - Type B
-No cross protection
-3 boosters, then annually prior to round bale season
-Proper storage of feed
-Care when using round bales

Question 14

What is polyneuritis equi?
Who does it affect?

Answer 14

Progressive granulomatous polyradiculoneuritis of the cauda equina and cranial nerves

Adult horses of any breed

Question 15

What causes Polyneuritis Equi?

Answer 15

-Unknown
-Cytotoxic T cell and macrophage infiltrates
-Autoimmune - allergic, gullian barre
-Hypersensitivity - systemic inflammation, parasite migration, EHV

Question 16

What are the clinical signs of polyneuritis equi?

Answer 16

-Cutaneous and muscular hyperesthesia around the hindquarters
-Progressive desensitization
-Progressive Paresis
-Progressive neurogenic atrophy
-Fecal retention with urinary incontinent
-Weakness and Ataxia
-Asymmetric muscle atrophy (Temporal or gluteal)
-Perfuse sweating

Question 17

What are some differentials for polyneuritis equi?

Answer 17

EPM, EHV, Encephalitis, trauma, Botulism

Question 18

How do you diagnose Polyneuritis Equi?

Answer 18

Clinical signs
CSF - mononuclear pleocytosis with high TP
Necropsy - thickened, discolored, edematous cauda equina, granulomatous inflammation, axonal degeneration and demyelination

Question 19

How do you treat polyneuritis equi?

Answer 19

Anti-inflammatories - steroids
Immunosuppressive Drugs
Palliative but not curative
Supportive Care - bladder cath, manual feces removal
Prognosis - hopeless

Question 20

What are some nerves that are affected by a peripheral neuropathy?

Answer 20

Facial, suprascapular (sweeney), Radial, Femoral, Sciatic (peroneal and tibial), obturator (foaling)

Question 21

What causes nerve injury?

Answer 21

Trauma, stretching, compression or severance

Question 22

Define the following:
Neuropraxia:
Axonotmesis:
Neurotmesis:

Answer 22

Neuropraxia: Brusing and inflammation of nerves (transient 3-6wk)
Axonotmesis: Crushing of nerve, epineurium and perineurium intact
Neurotmesis: Whole fiber severed, Wallerian degeneration expected

Question 23

How fast do regenerating axons grow?

Answer 23

1mm/day

Question 24

What is the progression of nerve dysfunction and damage?

Answer 24

-Loss of proprioceptive function (placement and mild ataxia)
-Paresis or paralysis of voluntary and reflex movements
-Desensitization

Question 25

What percent of muscle mass is lost by 2 weeks after denervation?

Answer 25

50% -Fibrosis will prevent healing and failure to heal beyond 12 months is a poor prognosis

Question 26

What causes facial nerve paralysis and what are the clinical signs?

Answer 26

Traumatic compression of facial crest, inflammation middle ear or guttural pouch, brainstem disease Signs: Ear droop, ptosis, muzzle deviation away from lesion, quidding

Question 27

What is the term for paralysis of the suprascapular nerve?

Answer 27

Sweeney - trauma to suprascapular nerve (trauma or chronic concussion) -Look like leg is asleep

Question 28

What are some clinical signs of Sweeny or suprascapular Nerve Paralysis?

Answer 28

-Walk like leg is asleep -Atrophy nerve -Abduction shoulder while weight bearing -Subluxation shoulder -Difficulty advancing limb

Question 29

What is the treatment for sweeny?

Answer 29

Acute Chronic (oa) Time and antinflammatories

Question 30

When does radial nerve paralysis occur?

Answer 30

Shoulder trauma/post anesthesia

Question 31

What are clinical signs of nerve paralysis?

Answer 31

Brachial plexus injury, elbow, knee or fetlock flexed, dorsum food on ground, elbow dropped bear weight poorly and not on all limbs

Question 32

What are some differentials for radial nerve paralysis?

Answer 32

Olecranon fracture Lameness (abscess)

Question 33

What is treatment for radial nerve paralysis?

Answer 33

Time and NSAID Support other limb to prevent laminitis