Small animal neuro neuromuscular disorders

Question 1

General signs of a myopathy

Answer 1

Proximal weakness; short strided gait, muscle atrophy
Normal postural reactions
Intact reflexes, sensation, pain

Get muscle fibre compensation so relatively normal exam; gait just short strided

Question 2

General signs of neuropathy

Answer 2

Distal weakness; paresis-plegia, neurogenic muscle atrophy
Postural deficity
Reduced reflexes
Reduction in sensation/pain

Question 3

What makes us suspicious that a neuromuscular disease is going on and not spinal

Answer 3

Loss of reflexes in all limbs and other changes such as dysphonia

Question 4

What spinal condition can present with all limbs affected

Answer 4

Spinal shock

Question 5

What serum biochemistry changes might we see with a muscle disorder

Answer 5

High CK
High K+

Question 6

What causes idiopathic polyradiculo-neuritis

Answer 6

Autoimmune disease; antibodies are formed against gangliosides so attack peripheral nerves esp nodes of ranvier

May be linked to cross reaction with campylobacter following eating contaminated chicken

Question 7

Clinical signs of idiopathic polyradiculoneuritis

Answer 7

Ascending motor paralysis over 24 hours (starting hind limbs)
Decreased then absent reflexes

Question 8

Diagnosis of idiopathic polyradiculoneuritis

Answer 8

By exclusion of other things on blood
CSF tap shows increased protein
Electrodiagnostics show much slower nerve condution

Could do anti-ganglioside antibody detection but this is poorly sensitive and not commercially available

Question 9

Treatment of idiopathic polyradiculoneuritis

Answer 9

Wait for spontaneous remission after a couple of months
May hospitalise early on to monitor for respiratry failure

Question 10

Why is ventroflexion of the neck so visible in cats c/f dogs

Answer 10

Cats don’t have a nuchal ligament

Question 11

What does ventroflexion of neck but normal reflexes point towards

Answer 11

A muscle issue
e,g hypokalaemic myopathy

Question 12

Why does low potassium cause gait changes

Answer 12

Low blood K+ causes K+ to move out from cells; reduces cell membrane potential (becomes more -ve)
–> therefore requires greater depolarisation to reach AP threshold so get weakness

Question 13

What underlying issue often leads to hypokalaemia that causes myopathy

Answer 13

Chronic kidney disease

Question 14

What type of disorder is myasthenia gravis

Answer 14

Synapse disorder

Question 15

What are typical presenting signs of a dog with myasthenia gravis

Answer 15

High muscle fatiguability; progressive weakness with exercise but better after rest
Intact reflexes

Question 16

Forms of myasthenia gravis

Answer 16

Generalised form
Focal farm affecting specific muscles; facial, laryngeal, pharyngeal and oesophageal

Question 17

Why is thymoma associated with myasthenia gravis

Answer 17

Because it has muscle like cells that express acetylcholine receptors and body may produce an auto-immune response to

Question 18

Why do we do radiographs conscious when looking for megaoesophagus

Answer 18

Because effects of GA can make normal oes look like megaoesophagus

Question 19

What will we see in a trace of repetitive nerve stimulation if an animal has myasthenia gravis

Answer 19

Stimulate 10X over and will see reduction in AP height each time

Question 20

What is the definitive diagnostic test fr myasthenia gravis

Answer 20

Acetyl choline receptor antibody levels

Question 21

Treatment for myasthenia gravis

Answer 21

Acetylcholinesterase inhibitors
Immunosuppressive therapy if ^^ not enough e.g steroids, azathioprin, cyclosporin

Question 22

Prognosis of myasthenia gravis

Answer 22

A third of cases have spontaneous remission after 6 months
Worse outcome if still have megaoesophagus after 6 months as continued risk of aspiration pneumonia

Question 23

Signs of brachial plexus avulsion

Answer 23

Monoparesis of the forelimb
Panniculus reflex deficit
Postural deficits
Anisocoria; since involves brachial plexus

Question 24

Signs pointing to brachial plexus tumour

Answer 24

Long term chronic lameness, older dog
Severe muscle atrophy
Reduced reflexes

Question 25

What type of tumours are usually seen in brachial plexus

Answer 25

Malignant nerve sheath tumour; poor outcome

Question 26

Signs of ischemic neuropathy from thromboembolism

Answer 26

Cat suddenly goes off back legs, cold hind feet

Question 27

What is the major causative factor of ischemic neuropathy

Answer 27

Hypertrophic cardiomyopathy; clot forms due to stasis, gets stuck at outer iliac bifurcation –> iscaemia