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Y3 Neurology > Neuromuscular Disorders > Flashcards

Neuromuscular Disorders Flashcards

1
Q

how do lower motor neurone disorders present?

A

weak, flaccid and wasted muscles
low tone
fasciculations
reduced/absent reflexes

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2
Q

what is the role of the neuromuscular junction?

A

makes the muscle contract by providing the connection between the motor neurone and the muscle

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3
Q

where do the motor neurones that innervate skeletal muscle fibres arise?

A

in the ventral horn of the spinal cord

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4
Q

what are motor end plates?

A

the synapses formed between motor neurons and muscles

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5
Q

how many motor neurons does each muscle cell respond to?

A

only one

however, a single motor neurone can control many muscle cells

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6
Q

what enzyme breaks down acetylcholine and what are the products?

A

acetylcholinesterase

acetate and choline

choline is sequestered into presynaptic vesicles

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7
Q

name two presynaptic disorders of the neuromuscular junction

A

botulism

lambert eaton myasthenic syndrome (LEMS)

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8
Q

what causes botulism?

A

clostridium botulinum

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9
Q

what is the pathophysiology of botulism?

A

botulinum toxin cleaves presynaptic proteins involved in vesicle formation, blockiung the vesicle from docking with the presynaptic membrane

this prevents muscle contraction

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10
Q

how does botulism present?

A

rapid onset weakness without sensory loss

ascending paralysis

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11
Q

what is the treatment for botulism?

A

supportive care

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12
Q

how long does botulism last?

A

around 12 weeks

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13
Q

what is the pathophysiology behind LEMS?

A

antibodies to presynaptic calcium channels lead to less vesicle release = reduced muscle contraction

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14
Q

what condition does LEMS have a strong association with?

A

underlying small cell lung carcinoma

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15
Q

how is LEMS managed?

A

3-4 diaminopyridine

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16
Q

name a postsynaptic disorder of the neuromuscular junction

A

myasthenia gravis

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17
Q

what is the pathophysiology behind myasthenia gravis?

A

autoimmune condition where antibodies to acetylcholine receptors (AChR) are produced

this reduces the number of functioning receptors causing muscle weakness and fatigue

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18
Q

what condition is myasthenia gravis associated with?

A

thymic hyperplasia/thymoma

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19
Q

when do symptoms start in myasthenia gravis?

A

when AChR levels reduced to 30% of normal

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20
Q

when are the two peaks of incidence of myasthenia gravis?

A

females in 20’s

males in 50’s-60’s

21
Q

what is the most common initial presentation of myasthenia gravis?

A

extraocular weakness
facial weakness
bulba weakness

then becomes generalised

22
Q

how does myasthenia gravis present?

A

fatigable weakness of skeletal muscle

23
Q

what is ocular myasthenia gravis?

A

when weakness remains only in the extraocular muscles

24
Q

what parts of the limbs are usually involved in myasthenia gravis?

A

proximal parts become weak

25
Q

how is myasthenia gravis diagnsoed?

A

serum AChR antibodies
single fibre EMG
CT chest to look for a thymoma

26
Q

what three things are included in the acute treatment of myasthenia gravis?

A

acetylcholinesterase inhibitor
IV Ig or plasma exchange
thymectomy if needed

27
Q

name an acetylcholinesterase inhibitor that can be given for myasthenia gravis

A

pyridostigmine

this improves muscle strength

28
Q

what emergency treatments can be given for myasthenia gravis?

A

IV immunoglobulin

plasma exchange

29
Q

what drugs can be given for long term myasthenia gravis management?

A

immunomodulating drugs

steroids

30
Q

what should be given alongside steroids in myasthenia gravis?

A

steroid sparing agents such as azathioprine or mycophenolate

31
Q

what antibiotic should be avoided in patients with myasthenia gravis?

A

gentamicin

32
Q

what is the smallest contractile unit of skeletal muscle?

A

the muscle fibre

33
Q

what is each skeletal muscle fibre surrounded by?

A

endomysium

34
Q

what is a fascicle and what encapsulates this?

A

20-80 smooth muscle fibres

encapsulated by perimysium

35
Q

what forms an individual skeletal muscle?

A

many smooth muscle fascicles surrounded by epimysium

36
Q

name six possible signs and symptoms of muscle disease

A 
myalgia 
weakness 
wasting 
hyporeflexia 
fasciculations 
myotonia
37
Q

what are fasciculations?

A

visible, fast, fine and spontaneous twitches

usually a sign of disease in the motor neuron, not the muscle

38
Q

what is myotonia?

A

failure of muscle relaxation after use

39
Q

when can fasciculations occur in normal muscles?

A

precipitated by stress, caffeine and fatigue

40
Q

what blood test is often done if muscle disease is suspected?

A

CK

elevated in many muscle disorders

41
Q

what is the characteristic feature of dermatomyositis?

A

heliotrope rash

42
Q

what underlying condition do many patients with dermatomyositis have?

A

malignancy

43
Q

how does polymyositis present?

A

symmetrical, progressive proximal weakness developing over weeks - months

raised CK

44
Q

what drug does polymyositis respond to?

A

steroids

45
Q

what is the most common type of muscular dystrophy?

A

myotonic dystrophy

46
Q

what is the inheritance pattern of myotonic dystrophy?

A

autosomal dominant

47
Q

how does myotonic dystrophy present?

A 
myotonia 
weakness 
cataracts 
ptosis 
frontal balding 
cardiac defects
48
Q

how does inclusion body myositis usually present?

A

slowly progressive weakness in the sixth decade of life with characteristic thumb sparing

Y3 Neurology (31 decks)

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