Principles of neuromuscular disease - READING

Question 1

What type of neuromuscular disease is polyradiculoneuritis?

Answer 1

ACUTE GENERALISED NEUROMUSCULAR DISEASE
- Neuropathy
o Inflammatory

Question 2

Describe polyradiculoneuritis

Answer 2

• Group of inflammatory diseases which affect nn roots and/or peripheral nn
• AETIOLOGY: immune-mediated or infectious disease, attach on peripheral nn or nn roots  axonal degeneration and some demyelination

Question 3

What type of neuromuscular disease is fulminant MG?

Answer 3

• ACUTE GENERALISED NEUROMUSCULAR DISEASE: - Juntionopathy - Idiopathic/paraneoplastic
• CHRONIC GENERALISED NEUROMUSCULAR DISEASE - Junctionopathy
• (FOCAL FORM) ACUTE FOCAL NEUROMUSCULAR DISEASE - junctionopathy - myasthenia gravis (focal)
• (FOCAL FORM) CHRONIC FOCAL NEUROUSCULAR DISEASE - neuropathy - junctionopathy

Question 4

Describe fulminant MG

Answer 4

• Fulminant MG is the least common subtype of acquired MG (

Question 5

What type of neuromuscular disease are botulism and tick paralysis?

Answer 5

ACUTE GENERALISED NEUROMUSCULAR DISEASE - Junctionopathy - toxic

Question 6

Describe botulism

Answer 6

• Flaccid neuromuscular paralysis d/t clostridial neurotoxin
• Symmetrical ascending weakness, death from respiratory paralysis. No changes in consciousness
• Ingestion of carrion or raw meat

Question 7

Describe tick paralysis

Answer 7

• Causes paralysis in dogs (and cats in Australia) produced by neurotoxin generated by some strains of certain spp of tick
• Flaccid afebrile ascending motor paralysis and progressive respiratory failure

Question 8

What type of neuromuscular disease is hypocalcaemia?

Answer 8

ACUTE GENERALISED NEUROMUSCULAR DISEASE - Junctionopathy - Metabolic

Question 9

Describe hypocalcaemia

Answer 9

• Most CS are associated with increased neuromuscular tissue excitability
• Mm trembling, twitching, fasciculation, occasional seizure
• Respiratory arrest is a possible acute presentation
• Possible causes: low concentrations of binding protein, chronic renal failure, puerperal tetany, acute pancreatitis

Question 10

What type of neuromuscular disease are hypokalaemia and exertional rhabdomyolysis?

Answer 10

ACUTE GENERALISED NEUROMUSCULAR DISEASE - myopathy - metabolic

Question 11

Describe hypokalaemia

Answer 11

• CS when serum [K+] falls below 2.5-3mmol/l
• Cause – excess loss or reduced intake
• CS –lethargy, fatigue, mm pain, crouched gait, ventroflexion of neck
• Burmese cats - hereditary (hypokalemic polymyopathy)

Question 12

Describe exertional rhabdomyolysis

Answer 12

• Usually affects athletic and working dogs (Greyhounds and Sled dogs)
• Results from extreme mm work to point that mm cells are damaged  secondary problems (range from minor mm pain to death)
• Few references in dogs, well documented in horses
• 3 categories: hyperacute exertional rhabdomyolysis (extreme stress with generalised mm pain), acute exertional rhabdomyolysis (dogs are distressed after race and painful when palpated), subacute rhabdomyolysis (dogs show suboptimal performance)

Question 13

What type of neuromuscular disease are immune-mediated polymyositis and paraneoplastic polymyositis?

Answer 13

CHRONIC GENERALISED NEUROMUSCULAR DISEASE - Myopathy - Inflammatory

Question 14

Describe immune-mediated polymyositis

Answer 14

 Diffuse inflammation of skeletal mm
 Large breed adult dogs most commonly (many GSDs, Boxers, Newfoundlands)
 CS – weak, lame, reluctance to exercise, stiff gait, exercise related progression of weakness, mm pain on palpation, mm atrophy, regurgitation d/t megaoesophagus
 Responsive to immunosuppressive therapy

Question 15

Describe paraneoplastic polymyositis?

Answer 15

 Usually related to auto-immune stimulation
 Frequency b/w neoplasia and this association is unknown
 Paraneoplastic MG strongly associated with presence of thymic disease.

Question 16

What type of neuromuscular disease are centronuclear myopathy, inherited myopathy, fibrotic myopathy (gracilis/ semitendinosus myopathy) and muscular dystrophy?

Answer 16

CHRONIC GENERALISED NEUROMUSCULAR DISEASE - Myopathy - Non-inflammatory

Question 17

Describe centronuclear myopathy

Answer 17

 Labrador retriever puppies
 Variable signs
 Genetic test for mutation in PTPLA gene and mm biopsy to confirm diagnosis
 Tx – none specific, nursing to stabilise by one year old

Question 18

Describe inherited myopathy

Answer 18

 Young Great Danes
 Generalised weakness and exercise intolerance, stiff gait
 Poor prognosis
 Pathophysiology: mm pathology  compromised mm function  atrophy  CS

Question 19

Describe fibrotic myopathy (gracilis / semitendinosus myopathy)

Answer 19

 Horses – adult quarterhorse and stockhorse
 Trauma to mm  restricted movement, abnormal gait, decreased mm mass
 Tx – sx excision of affected tissue and tenotomy

Question 20

Describe muscular dystrophy

Answer 20

 d/t low amounts of dystrophin  progressive mm degeneration
 usually Golden Retrievers, can be any breed
 Duchenne is the most common form in canines
 Males usually because X linked recessive
 CS from 6-8 weeks of age
 Research into Stem Cell therapy

Question 21

What type of neuromuscular disease are trigeminal neuropathy and facial neuropathy?

Answer 21

ACUTE FOCAL NEUROMUSCULAR DISEASE - Neuropathy - Idiopathic

Question 22

Describe trigeminal neuropathy

Answer 22

• Can be d/t infiltrating neoplasia
• CN 7 and SNS may also be involved
• CS usually unilateral termporalis and masseter mm ipsilateral to lesion

Question 23

Describe facial neuropathy

Answer 23

• Paresis or paralysis is most common abnormality seen with facial nerve disease which can occur as an idiopathic condition (especially Cocker Spaniels) as a result of OM/ OE, with trauma and with tumour of middle ear canal

Question 24

What type of neuromuscular disease are brachial plexus avulsion, femoral nerve injury, sciatic nerve injury and caudal nerve (tail- pull injury)?

Answer 24

ACUTE FOCAL NEUROMUSCULAR DISEASE - Neuropathy - Trauma

Question 25

Describe brachial plexus avulsion

Answer 25

* d/t trauma, often RTA * Neurological deficits apparent immediately following injury. Neurogenic atrophy takes 7-10d to develop. * CS: complete absence of limb function, dropped elbow with carpal flexion, affected limb looks longer, complete absence of sensation in distal limb * Partial Horner’s in 55% cases * Brachium advanced when dog is walking

Question 26

Describe femoral nerve injury

Answer 26

* Uncommon as isolated peripheral lesion since nerve well protected by mm * D/t pressure on medial thigh * CS: unable to extend stifle, non-weight bearing, no patellar reflex, decreased skin sensation medial thigh, stifle, lower limb and quadriceps atrophy

Question 27

Describe sciatic nerve injury

Answer 27

* d/t pelvic, lumbar and sacrococcygeal fractures, foraminal stenosis, sx in pelvic and perineal area and others * CS: lameness or LMN paresis

Question 28

Describe caudal nerve (tail-pull) injury

Answer 28

* Often with pelvic trauma, secondary to RTA * Accompanied by damage to nerve to tail, bladder, perineum and anus (L4-S3) * Various CS: local hyperaesthesia, flaccid tail paralysis, swelling around tail base, dribbling urine

Question 29

What type of neuromuscular disease is ischaemic neuromyopathy?

Answer 29

* ACUTE FOCAL NEUROMUSCULAR DISEASE - neuropathy/myopathy - vascular * ACUTE

Question 30

Describe ischaemic neuromyopathy

Answer 30

* d/t thromboembolism (cats with cardiomyopathy – HCM in cats mean age 5yo, DCM in older cats, also hyperthyroidism and hypercoagulable conditions * CS: depend on location

Question 31

Describe focal myasthenia gravis (MG)

Answer 31

* Only affects extraocular mm, oesophagus and mm innervated by CN 5, 7 & 9 * Present with laryngeal, pharyngeal, facial and oesophageal dysfunction (vs. generalised form which present with non-ambulatory tetraparesis and dyspnoea)

Question 32

What type of neuromuscular disease are masticatory muscle myositis (MMM) and extraocular myositis?

Answer 32

ACUTE FOCAL NEUROMUSCULAR DISEASE - myopathy - inflammatory

Question 33

Describe masticatory muscle myositis (MMM)

Answer 33

* Common autoimmune inflammatory myopathy * Focal inflammation of digastricus, temporalis, pterygoid, masseteric as masticatory mm are composed of a specific type of myofibres (type 2M) and CD8+ TC initiate their destruction via autoantibodies. * Large dog breeds, median age 2 years * 2 forms: acute and chronic

Question 34

Describe extraoxular myositis

Answer 34

* Larger breed dogs, especially Golden Retriever * Females, 6-24 months old * Relatively uncommon

Question 35

Describe recumbency / compartment syndrome

Answer 35

* When the tissue pressure within a closed mm compartment exceeds the perfusion pressure and results in mm and nn ischaemia * Usually subsequent to trauma (e.g. fracture)

Question 36

What type of neuromuscular disease is degenerative lumbosacral stenosis (DLSS)?

Answer 36

CHRONIC FOCAL NEUROMUSCULAR DISEASE - Neuropathy - Degenerative

Question 37

Describe degenerative lumbosacral stenosis (DLSS)

Answer 37

* Common cause of cauda equina syndrome * Relatively frequent neuro condition of older dogs * Applies to syndromes affecting spinal cord segments, spinal nerve roots, spinal nerves (sciatic nerve  perineum, bladder, urethral and anal sphincters, tail) * Lumbosacral disease encompasses any pathologic condition that affects the region of the spinal cord segments that contribute to the sciatic nerve and sacral and caudal nerves. Cauda equina syndrome implies pathologic conditions that affect the last several pairs of spinal nerve roots.

Question 38

What neoplasias can cause chronic focal neuromuscular disease - neuropathy - neoplasia?

Answer 38

- peripheral nerve sheath tumour - lymphoma - meningioma

Question 39

Describe peripheral nerve sheath tumour

Answer 39

* 25% of canine nervous system tumours * A type of intra-dural extra-medullary tumour * Commonly middle to low cervical nerve roots and brachial plexus. Sometimes also trigeminal nerve, thoracic nerves and lumbosacral plexus. Thoracic limb often affected * CS: peripheral nn deficits and mm atrophy * Tumour of nn sheath  interruption of nn conduction  loss of function of target organ  mm atrophy where skeletal mm affected

Question 40

Describe CNS lymphoma

Answer 40

* One form is CNS form | * Commonest haemopoietic neoplasm (8-10% of all canine malignant

Question 41

Describe meningioma

Answer 41

* Commonest brain neoplasm * Usually benign, slow growing * Mostly on floor of cranial cavity, over convexitis of cerebral hemispheres or over cerebellum and olfactory lobes * CS: seizures, insidious onset neuro signs, focal CS

Question 42

List some chronic focal neuromuscular diseases causing myopathies

Answer 42

o Inflammatory: Masticatory myositis ad Extraocular myositis – o Non-inflammatory: Fibrotic myopathy (gracilis/ semitendinosus myopathy)