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NEUROLOGY > Disorders of the neuromuscular junction and muscle > Flashcards

Disorders of the neuromuscular junction and muscle Flashcards

1
Q

What are motor end plates?

A

Synapses which form between motor neurones and the muscle

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2
Q

Describe the locations of endomysium, perimysium and epimysium

A

Endomysium surrounds muscle fibres

Perimysium surrounds fascicles

Epimysium surrounds individual muscles

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3
Q

Describe the different muscle fibre types

A

Type I - slow oxidative, faitgue resistant

Type IIa - fast oxidative, aerobic metabolism

Type IIb - fast glycolytic, easily fatigues

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4
Q

Give examples of presynaptic disorders

A

Botulism

Lambert eaton myasthenic syndrome (LEMS)

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5
Q

Which organism causes botulism and where is it found?

A

Clostridium botulinum

Organism present in soil which can infect food and wounds

IVDU can become infected if their drugs are not clean

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6
Q

How does botulism present?

A

Neuromuscular and respiratory weakness

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7
Q

What is lambert eaton myasthenia syndrome?

A

A paraneoplastic syndrome with antibodies to presynaptic calcium channels

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8
Q

How does lambert eaton myasthenia syndrome present?

A

Affects large muscles - patient struggles to get up

Symptoms improve with exercise

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9
Q

Lambert eaton myasthenia syndrome is strongly associated with which condition?

A

Small cell carcinoma

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10
Q

How is lambert eaton myasthenia syndrome treated?

A

3-4 diaminopyridine

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11
Q

Give an example of a postsynaptic disorder

A

Myaesthenia Gravis

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12
Q

Which antibodies are involved in myasthenia gravis?

A

Anti AChR

Anti Musk

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13
Q

What is the most common disorder of the neuromuscular junction?

A

Myasthenia Gravis

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14
Q

Who gets myasthenia graves?

A

More common in females

Presents in females in the 3rd decade

Presents in males in the 6th or 7th decade

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15
Q

What is the pathophysiology behind myasthenia gravis?

A

Reduced numbers of functioning (ACh) receptors leads to muscle weakness and fatigueabillity

Flattening of endplate folds

75% of patients also have hyperplasia of the thymus

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16
Q

Describe the clinical presentation of myasthenia gravis

A

Fluctuating weakness

Diplopia and bilateral ptosis (EO muscle weakness)

Tired chewing meals (facial and bulbar muscle weakness)

Proximal limb weakness

Respiratory muscle weakness (late presentation)

17
Q

How can myasthenia graves be treated acutely and chronically?

A

ACUTE TREATMENT
Acetylcholinesterase inhibitors
IV immunoglobulin
Thymectomy

CHRONIC TREATMENT
High dose steroids and steroid sparing agents
Plasma exchange or immunoglobulin

18
Q

Which medication needs to be avoided in patients with myasthenia gravis due to the risk of myasthenia crisis?

A

Gentamicin

19
Q

What are fasciculations and what causes them?

A

Fast spontaneous twitches in muscle

May occur in healthy muscle and be precipitated by stress, caffeine and fatigue

May occur in denervated muscle which has become hyper excitable

20
Q

What is myotonia?

A

Failure of muscle relaxation after use

21
Q

What is myalgia?

A

Muscle weakness, wasting and hyporeflexia

22
Q

What causes rhabdomyolysis?

A

Extreme exercise

Falls

Crush injuries

Acute renal failure and DIC

23
Q

What is rhabdomyolysis?

A

Damage to skeletal muscle causes leakage of toxic intracellular contents into plasma

24
Q

What triad of symptoms does rhabdomyolysis present with?

A

Myalgia, muscle weakness and myoglobinuria

25
Q

Give examples of immune mediated muscle disorders

A

Polymyositis

Dermatomyositis

26
Q

Describe polymyositis

A

Symmetrical proximal muscle weakness develops over weeks to months

Raised CK

Responds to steroids

27
Q

Describe dermatomyositis

A

Clinically similar to polymyositis but with skin lesions

Helioptrope rash on the face

Big association with underlying malignancy

28
Q

What is inclusion body myositis?

A

A degeneratie muscle disorder

Slowly progressive weakness

Characteristic sparing of the thumb

Occurs age >60

29
Q

Give examples of inherited muscular disorder

A

Duchenne and Beker muscular dystrophies

Myotonic dystrophy

30
Q

Describe the genetics of myotonic dystrophy

A

Most common of the muscular dystrophies

Autosomal dominant inherited disorder

Trinucleotide disorder with anticipation

31
Q

Describe how myotonic dystrophy presents

A

Multisytem

Weakness

Cataracts and ptosis

Frontal balding

Cardiac defects

32
Q

What drugs can cause myopathy?

A

Corticosteroids

Statins

Amiodarone

Diuretics

Oral contraceptive

NEUROLOGY (18 decks)

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