Principles of Neuromuscular Disease Flashcards

1
Q

What makes up the neuromuscular system?

A
  1. Nerves (LMNs)
  2. Neuromuscular junction
  3. Skeletal muscle
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2
Q

What are the types/locations of neuromuscular disease?

A
  1. Neuropathy
  2. Junctionopathy
  3. Myopathy
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3
Q

When defining the problem, what two cardinal signs help you suspect neuromuscular disease?

A
  1. Weakness WITHOUT ataxia
    i. Short strides
    ii. Stilted gait
    iii. Not ataxic
  2. Exercise intolerance
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4
Q

What history and physical exam findings may make you suspicious of neuromuscular disease?

A
Hx:
Dysphagia
Dysphonia
Regurg
Dyspnoea
Gait abnormality

PE:
Muscle atrophy
Muscle hypertrophy
Myalgia

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5
Q

When you have weakness, what system could be involved?

A
  1. CVRS
  2. Systemic/metabolic
  3. Neurological
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6
Q

When working up a weakness case how can you rule out CVRS dz?

A
History of cough/CHF
PE: Murmur, arrhythmia, hypotension, pulses
Diagnostic test:
NIBP
Thoracic xray
Echocardiography
Cardiac toponin I
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7
Q

When working up a weakness case how can you rule out systemic/metabolic dz?

A

Pale MM, pyrexia, distended abdomen
Diagnostics:
Haem and biochem

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8
Q

If you have a cat with severe cervical ventroflexion, what electrolyte could be involved?

A

Myopathy related to hypokalaemia

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9
Q

If you have a dog that is very weak with marked fine tremors, what electrolyte could be involved?

A

Hypocalcaemia

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10
Q

How can you define the system in neurological cases?

A
  1. Is the patient neurologically normal or abnormal

2. Where is the lesion

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11
Q

What does a palmigrade/plantigrade posture suggest?

A

Seen in cats with neuropathies

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12
Q

Are the postural reactions usually normal or abnormal in a neuromuscular diseased animal?

A

May be normal - support their weight

Some so weak they cannot show proprioception

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13
Q

When are spinal reflexes reduced?

A

Neuropathy

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14
Q

What is marked muscle atrophy suggestive of?

A

Neuropathy (denervation atrophy).

Much more marked than disuse atrophy

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15
Q

What are the possible locations for neuromuscular disease?

A

Generalised
Focal (Cranial nerves)
Focal (Spinal nerves)

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16
Q

What would help you define the location to a neuropathy?

A

Reduced to absent spinal reflexes
Plantigrade/palmigrade stance
Reduced to absent muscle tone
+/- Neurogenic muscle atrophy

17
Q

What would help you define the location to a junctionopathy?

A

Normal to reduced spinal reflexes

Exercise intolerance

18
Q

What would help you define the location to a myopathy?

A

Often normal spinal reflexes
Exercise intolerance
+/- myalgia, muscle atrophy/hypertrophy

19
Q

Is it always possible to localised to neuropathy/junctionopathy/myopathy?

A

Often not possible to go further than localising to neuromuscular
Most marked and severe signs tend to be neuropathies

20
Q

What diagnostic tests can you perform to localise neuropathy/junctionopathy/myopathy?

A
Muscle enzymes (myopathy)
Increased CK
Increased AST
Increased ALT
Urinalysis (myopathy)
Myoglobinuria (dark brown urine)
Electrodiagnostics
21
Q

What is electromyography?

A

Cannot determine aetiology
Needle into muscle and detect spontaneous electrical activity
Spontaneous activity = muscle pathology/denervated
Silent = normal muscle/disuse atrophy
Neuropathy or myopathy (rules out junctionopathy and metabolic cause)

22
Q

What are nerve conduction studies?

A

Look further at nerve itself - stimulation
Differentiate neuropathy and myopathy
Neuropathy = decreased amplitude/slowed conduction velocity
Myopathy = normal

23
Q

How can neuromuscular ddx be grouped?

A
  1. Generalised acute
  2. Generalised chronic
  3. Focal acute
  4. Focal chronic
24
Q

Give some examples of generalised acute neuromuscular differentials…

A
Acute canine polyradiculoneuritis
Acquired myasthenia gravis
Botulism
Hypocalcaemic
Hypokalaemia
25
Q

Give some examples of generalised chronic neuromuscular differentials…

A

Inherited/breed specific polyneuropathy
Diabetic polyneuropathy
Myasthenia gravis
Hypokalaemia

26
Q

Give some examples of acute focal neuromuscular differentials….

A
Trigeminal neuropathy
Facial neuropathy
Brachial plexus avulsion
Myasthenia gravis
Masticatory myositis
27
Q

Give some examples of chronic focal neuromuscular differentials…

A

Degenerative lumbosacral stenosis
Peripheral nerve sheath tumour
Myasthenia gravis
Masticatory myositis

28
Q

What further diagnostic tests can be done in a neuromuscular disease case?

A
- All neuromuscular cases:
Haem
Biochem
Urinalysis
- Suspicion of endocrine:
ACTH stim
T4/TSH
- Suspicion of systemic dx:
Thoracic/abdominal imaging
- Serology
- Advanced imagine
- CSF analysis
- Last resort = nerve and muscle biopsies
29
Q

What do 80% dogs with acquired myasthenia gravis have?

A

Megaoesophagus and aspiration pneumonia

30
Q

What serology can you perform in a neuromuscular case?

A
- Acquired myasthenia gravis:
Nicotinic ACh receptor antibody titre
- Masticatory myositis:
Type 2M muscle fibre antibody titre
- Infectious agents:
Toxo/neospora
FeLV/FIV
31
Q

General considerations for tx of neuromuscular disease…

A
  • Recumbent patients require supportive care, fliuds, nutrition, bladder managemet
  • Severe weakness may lead to resp muscle weakness - ventilate
  • PHYSIO and HYDROTHERAPY essential to maintain muscle mass
32
Q

What is dysphonia?

A

A change in vocalisation

33
Q

Why does neuromuscular disease present as weakness without ataxia?

A

Spinal cord and brain not affected

34
Q

Why might patients with a junctionopathy appear normal prior to exercise?

A

Junctionopathies tend not to cease all transmission, the neuromuscular junction simply becomes less efficient

35
Q

What is the role of edrophonium?

A

Anticholinesterase (increases acetylcholine in neuromuscular junction)

36
Q

Describe the edrophonium response test

A

Intravenous bolus of edrophonium will allow animals with myasthenia gravis to be able to walk for longer