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Y3 - Neuro > Neuromuscular Junction Disease > Flashcards

Neuromuscular Junction Disease Flashcards

1
Q

What is myasthenia gravis?

A

An autoimmune condition associated with the production of antibodies against nicotinic receptors at the NMJ causing fluctuating and fatiguing muscle weakness

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2
Q

What antibodies are involved in myasthenia gravis?

A

Anti-ACh receptor

Anti MuSK

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3
Q

What is the pathophysiology of myasthenia gravis?

A

Antibodies act at the NMJ to reduce the overall number of functional receptors leading to muscle weakness and fatiguability

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4
Q

What conditions are associated with myasthenia gravis?

A

Disease of the thymus
SLE
Rheumatoid arthritis

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5
Q

In myasthenia gravis what is the muscle weakness worsened by?

A

Pregnancy
Emotion
Exercise
Drugs: beta blockers, opiates, gentamicin, tetracyclines

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6
Q

Who presents with myasthenia gravis?

A

F>M

2 peaks of incidence: women - early 30s, men - 6-7th decades

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7
Q

What is the main clinical feature of myasthenia gravis?

A

Muscle weakness that gets worse throughout the day and with repeated use of the muscle

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8
Q

What order are the muscle groups affected in myasthenia gravis?

A

Ocular
Bulbar
Face
Neck, limb girdles, trunk, laryngeal muscles

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9
Q

What are the ocular symptoms of myasthenia gravis?

A

Double vision

Ptosis

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10
Q

What are the bulbar symptoms of myasthenia gravis?

A

Dysphagia
Difficulty chewing
Dysarthria

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11
Q

What are the facial symptoms of myasthenia gravis?

A

Drooping of facial muscles

Snarled expression with smiling

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12
Q

What are the neck, limb girdles, trunk, laryngeal muscle symptoms of myasthenia gravis?

A

Trunk involvement - difficulty breathing
Laryngeal muscles - quietening of voice
Difficulty holding up head

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13
Q

What do you see on examination in myasthenia gravis?

A 
Snarled expression
Ptosis
Peek sign - sclera shows when patients close their eyes
Normal sensation and reflexes
Normal muscle appearance and tone
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14
Q

What investigations are done in myasthenia gravis?

A

Immunoloy (anti-AChR, anti-MuSK)
Neurophysiology - single fibre EMG
CT thorax to assess for thymoma

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15
Q

What is seen on single fibre EMG in myasthenia gravis?

A

Single fibre jitter
Low amplitude action potentials
Decremental decrease in muscle twitches with repeated stimulation

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16
Q

What is the management of myasthenia gravis?

A

Pyridostigmine (anti-cholinesterase)
Thymus abnormality - thymectomy
Relapses - prednisolone

17
Q

How does Pyridostigmine work for management of myasthenia gravis?

A

Works by reducing the rate of ACh breakdown in the synapse and therefore increases activity of ACh
Help weakness but do not alter course of disease

18
Q

What are the side effects of Pyridostigmine?

A 
Diarrhoea
Colic pain (reduced by an anti-muscarinic)
19
Q

What is a myasthenic crisis?

A

Severe relapse of myasthenia gravis resulting in weakness of respiratory muscles and difficulty breathing

20
Q

What is the management of a myasthenic crisis?

A

Ventilatory support

Immunoglobin or plasmaphoresis

21
Q

What is Lambert-Eaton Myasthenic Syndrome?

A

A rare disease of pre-synaptic calcium channels resulting in muscle weakness

22
Q

What is the pathophysiology of Lambert-Eaton Myasthenic Syndrome?

A

Reduced function of calcium channels limits the amount of ACh that can be released from presynaptic terminals

23
Q

What are the causes of Lambert-Eaton Myasthenic Syndrome?

A 
Autoimmune - anti P/Q CGCC antibodies
Paraneoplastic syndromes (esp small cell lung cancer)
24
Q

What is the presentation of Lambert-Eaton Myasthenic Syndrome?

A

Muscle weakness similar to myasthenia gravis

25
Q

How is Lambert-Eaton Myasthenic Syndrome differentiated from myasthenia gravis?

A

Improvement with exercise
Primarily limb symptoms leading to gait disturbance
Autonomic involvement (dry mouth, constipation, impotence)
Hyporeflexia (again improves with exercise)

26
Q

What investigations are done for Lambert-Eaton Myasthenic Syndrome?

A

Immunology (anti P/Q CGCC antibodies)
Neurophysiology
CT CAP screen for malignancy

27
Q

What is seen in neurophysiology in Lambert-Eaton Myasthenic Syndrome?

A

Low frequency muscle action potentials
Increase in twitch amplitude with exercise
Increase in abductor digiti minimi fasciculation with exercise

28
Q

What is the management for Lambert-Eaton Myasthenic Syndrome?

A

3,4 Diaminopyradine

IV immunoglobulins

29
Q

What is botulism?

A

Infection with clostridium botulinum

30
Q

What are associated with acquiring botulism?

A

IVDU

Penetrative wounds

31
Q

How does clostridium botulinum cause symptoms?

A

Toxin blocks the release of ACh in presynaptic terminals

32
Q

What is the presentation of botulism?

A

Afebrile
Flaccid paralysis
Rapid onset (hours)
Weakness without sensory loss

33
Q

What is the management of botulism?

A

Anti-toxin

Improves on its own in about 12 weeks

Y3 - Neuro (14 decks)

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