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Myasthenia Gravis Flashcards

1
Q

What is myasthenia gravis?

A

Autoimmune condition that causes muscle weakness that becomes worse with activity but improves with rest

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2
Q

Myasthenia gravis affects women and men at different ages

What is the typical age for each gender?

A

Women under 40

Men over 60

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3
Q

Myasthenia gravis is linked with what kind of tumours?

A

Thymoma - tumour of the thymus gland

About 10-20% of patients with MG will have a thymoma, and about 20-40% of Thymoma patients will develop MG

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4
Q

Pathophysiology of Myasthenia gravis - 85% of MG patients produce which antibodies?

A

85% of MG patients - their immune system produces acetylcholine receptor antibodies - bind to postsynaptic neuromuscular junction receptor (acetylcholine receptors) and block the receptors - prevents ach from stimulating receptor and trigger muscle contraction
Receptors become blocked more in activity - less effective stimulation of muscle
More muscle weakness the more the muscles are used

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5
Q

Pathophysiology of Myasthenia gravis - 15% of MG patients produce which antibodies?

A

Muscle specific kinase and low-density lipoprotein receptor related protein 4 (MUSK AND LRP4)
Organise the acetylcholine receptor - inadequate ones being created and organised
Causes symptoms of MG

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6
Q

How do myasthenia gravis patients present?

A

May be mild and subtle or life threatening/severe

Weakness - worse with muscle use and better with rest
Minimal in morning, worse at end of day

Proximal muscles and small muscles of head and neck - leading to extra ocular muscle weakness causing double vision (diplopia) and eyelid muscle drooping (ptosis)
Also facial muscle weakness, swallowing issues, fatigue in jaw and slurred speech

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7
Q

What is most affected in myasthenia gravis?

A

Proximal muscles and small muscles of head and neck - leading to extra ocular muscle weakness causing double vision (diplopia) and eyelid muscle drooping (ptosis)
Also facial muscle weakness, swallowing issues, fatigue in jaw and slurred speech

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8
Q

Exam on a patient presenting with myasthenia gravis

A

Repeated blinking - exacerbate ptosis
Look upwards (upward gazing) - diplopia will get worse
Repeat abduction of shoulder - 20x - result in unilateral weakness when you compare both sides
Check for a thymectomy scar
Forced vital capacity - strength in muscles of respiration

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9
Q

Diagnosis of myasthenia gravis - what do we check for? (4) and what test can be done if in doubt about the diagnosis?

A

Ach-receptor antibodies (85%)
Musk antibodies (10%)
LRP4 (<5%)
CT/MRI of thymus gland to check for thymoma
Edrophonium test - if doubt about diagnosis

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10
Q

Edrophonium test for myasthenia gravis - what is this?

A

Patients are given an IV dose of Edrophonium chloride (or neostigmine)
Cholinesterase enzymes in the neuromuscular junction which break down acetylcholine - reduce the action
Edrophonium or neostigmine block the cholinesterase enzymes and therefore prevent the break down of acetylcholine
As a result, ach increases at NMJ
Drugs briefly relieve the weakness
Aim - to improve it temporarily which helps to establish the diagnosis

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11
Q

Treatment options for myasthenia gravis

A

1) Acetylcholinesterase inhibitors (pyridostigmine or neostigmine)
2) Immunosuppression with steroids or azathioprine to suppress antibody production
3) Thymectomy can improve symptoms in patients even without a thymoma
4) Monoclonal antibodies - such as rituximab (targets B cells, reduces antibody production - NHS available if certain criteria met) OR
- eculizumab - C5 complement target - may prevent complement activation caused by the acetylcholine receptor antibodies and prevent distruction of ACH receptors (ongoing research about whether it should be offered by NHS - not currently recommended by NICE)

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12
Q

1) Acetylcholinesterase inhibitors for myasthenia gravis - name 2

A

1) Acetylcholinesterase inhibitors (pyridostigmine or neostigmine)

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13
Q

What monoclonal antibody is available on the NHS for myasthenia gravis if certain criteria is met?

A

rituximab (targets B cells, reduces antibody production - NHS available if certain criteria met)
Other is eculizumab but not currently on NHS/ recommended by NICE

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14
Q

Myasthenic crisis - what is it and what it the management?

A

Severe complication of myasthenia gravis
Can be life threatening
Acute worsening of symptoms (often caused by another infection such as a respiratory tract infection)
Can lead to respiratory failure as a result of weakness in the muscles of respiration
May require non invasive ventilation with BIPAP or full intubation and ventilation to support

Treatment - immunomodulatory therapy such as IV immunoglobulins and plasma exchange to try to remove the antibodies

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15
Q

Myasthenia gravis is a neuromuscular disorder, which is characterised by … and ….

A

Myasthenia gravis is a neuromuscular disorder, which is characterised by weakness and fatiguability.

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16
Q

MG is predominantly due to the formation of … receptor antibodies

A

MG is predominantly due to the formation acetylcholine receptor antibodies (AChR-Ab) that bind to acetylcholine (ACh) receptors at the neuromuscular junction (NMJ). This prevents binding of ACh and subsequent depolarisation needed for muscular contraction. The hallmark of MG is fatiguability, which refers to increasing muscle weakness with repeated use.

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17
Q

The prevalence of MG is estimated at … per 100,000 population within the UK.

A

The prevalence of MG is estimated at 15 per 100,000 population within the UK.

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18
Q

MG has a variable annual incidence of 7-23 per million people. The prevalence of the condition has been … over the last few decades

A

MG has a variable annual incidence of 7-23 per million people. The prevalence of the condition has been increasing over the last few decades with improved mortality, better recognition and ageing population.

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19
Q

MG can occur at any age and it has a bimodal peak in incidence:

2nd-3rd decade of life: predominantly …
6th-7th decade of life: predominantly …

A

MG can occur at any age and it has a bimodal peak in incidence:

2nd-3rd decade of life: predominantly females
6th-7th decade of life: predominantly males

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20
Q

The majority of patients with MG secondary to AChR-Abs have evidence of … abnormalities.

A

The majority of patients with MG secondary to AChR-Abs have evidence of thymic abnormalities. The thymus is a bilobed lymphoid organ important in the development of T lymphocytes (i.e. T cells), which is situated in the anterior superior mediastinum of the thorax.

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21
Q

In MG, 10-15% of patients have a thymoma (rare benign tumour of thymus gland) and up to 85% have thymic …. The disease may even improve or regress with removal of the thymus gland.

A

In MG, 10-15% of patients have a thymoma (rare benign tumour of thymus gland) and up to 85% have thymic hyperplasia. The disease may even improve or regress with removal of the thymus gland.

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22
Q

thymoma - what is this?

A

(rare benign tumour of thymus gland)

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23
Q

The importance of the thymus in MG is related to … cells.

A

The importance of the thymus in MG is related to myoid cells. Myoid cells in the thymus resemble skeletal muscle cells and even possess the ACh receptor. It is thought these cells are central to the development of autoimmunity to ACh receptors. For these reasons, investigating for thymic abnormalities is critical in MG and many patients may be offered surgical removal.

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24
Q

MG is associated with other autoimmune diseases including … (3)

A

MG is associated with other autoimmune diseases including Graves’ disease, systemic lupus erythematous, and rheumatoid arthritis, among others.

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25
Q

The NMJ is important for …-… coupling. This refers to the process of converting an action potential that terminates at a NMJ, which is a chemical synapse between motor neuron and muscular fibre, into muscular contraction.

A

The NMJ is important for excitation-contraction coupling. This refers to the process of converting an action potential that terminates at a NMJ, which is a chemical synapse between motor neuron and muscular fibre, into muscular contraction.

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26
Q

In MG, AChR-Abs bind to ACh-R on the motor end-plate of skeletal muscle, which blocks the binding of ACh. This is an example of a type … hypersensitivity reaction (antibody-mediated). Smooth muscle and cardiac muscle are not usually affected by the disease.

A

In MG, AChR-Abs bind to ACh-R on the motor end-plate of skeletal muscle, which blocks the binding of ACh. This is an example of a type II hypersensitivity reaction (antibody-mediated). Smooth muscle and cardiac muscle are not usually affected by the disease.

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27
Q

AChR-Ab binding affects the NMJ is several ways:

A

Blockage of ACh binding
Cross linking of ACh-R, internalisation and destruction: global reduction in the number of ACh receptors able to contribute to muscular contraction, particularly on repeated use of the muscle
Complement-mediated destruction of membrane: damage to post-synaptic membrane via the membrane attack complex (MAC). Limits the surface area available for insertion of new AChRs.

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28
Q

Clinical subtypes of myashthenia gravis

A

Ocular MG: weakness limited to eyelids extraocular muscles. Only 50% seropositive.
Generalised MG: can affect numerous muscle groups including neck, bulbar, limbs, respiratory and ocular. Up to 90% seropositive.

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29
Q

Antibody subtypes - myasthenia gravis (4)

A

MG with AChR-Ab: 80-90% of cases
MG with Anti-MuSK: ~4% of cases
MG with Anti-LRP4: ~2% of cases
Seronegative myasthenia

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30
Q

Thymic abnormalities in myasthenia gravis (4)

A

Normal
Thymoma: 10-15% of patients with MG
Hyperplasia
Atrophy

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31
Q

Patients without detectable autoantibodies are said to have … MG.

A

Patients without detectable autoantibodies are said to have seronegative MG.

Traditionally, patients with MG who did not have AChR antibodies were classified as ‘seronegative’. Approximately, 50% of these patients have been identified to have another autoantibody known as muscle-specific receptor tyrosine kinase (MuSK). Other autoantibodies involved in the pathogenesis of MG has been identified including anti-lipoprotein receptor-related protein 4 (LRP4). Both MuSK and LRP4 are important in the normal function of the NMJ.

Now, patients without AChR, MuSK or LRP4 autoantibodies are classified as seronegative MG. Other autoantibodies have been associated with MG in both seropositive and seronegative cases (e.g. anti-striated muscle antibodies).

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32
Q

Now, patients without AChR, MuSK or LRP4 autoantibodies are classified as … MG.

A

Now, patients without AChR, MuSK or LRP4 autoantibodies are classified as seronegative MG. Other autoantibodies have been associated with MG in both seropositive and seronegative cases (e.g. anti-striated muscle antibodies).

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33
Q

MG is broadly classified into two clinical forms: ocular and …

A

MG is broadly classified into two clinical forms: ocular and generalised.

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34
Q

The hallmark clinical feature of MG, in both ocular and generalised, is fluctuating … … ….

A

The hallmark clinical feature of MG, in both ocular and generalised, is fluctuating skeletal muscle weakness. This usually presents with fatiguability that refers to increased muscle weakness on repeated use.

35
Q

This shows clinical features of…

A

Myasthenia gravis

36
Q

Ocular symptoms in myasthenia gravis

A

More than 50% present with ocular symptoms

Diplopia: double vision. Should improve on closing, or occluding, one eye.
Ptosis: drooping of upper eyelid. May be asymmetrical and fluctuant. May be enhanced on prolonged upward gaze.
Weak eye movements: unusual pattern of weakness that does not correlated to a single nerve or muscle (helping differentiate it from a cranial nerve palsy)
Pupillary sparing: no evidence of abnormally small or large pupils and react to light.

37
Q

Around …% of patients with ocular myasthenia will develop generalised disease within two years of onset. Furthermore, up to …% will only have ocular symptoms throughout their disease course.

A

Around 50% of patients with ocular myasthenia will develop generalised disease within two years of onset. Furthermore, up to 25% will only have ocular symptoms throughout their disease course.

38
Q

Generalised symptoms in myasthenia gravis

A

Approximately 15% present with bulbar symptoms and 5% with limb weakness alone

Bulbar muscles: fatiguable chewing, dysarthria, dysphagia.
Facial muscles: expressionless face. Poor smile or classical ‘myasthenic sneer’ (mid lip rises but outer mouth corners fail to move)
Neck muscles: extensor and flexor muscles can be affected. May get ‘dropped-head syndrome’ towards end of day.
Limb muscles: mainly proximal muscle weakness. Arms affected more than legs
Respiratory muscles: most serious presentation. Can lead to respiratory failure, which is life-threatening. May present with myasthenic crisis (discussed below). May occur spontaneously or be precipitated*.

39
Q

What is the most serious presentation in myasthenia gravis?

A

Respiratory muscles: most serious presentation. Can lead to respiratory failure, which is life-threatening. May present with myasthenic crisis. May occur spontaneously or be precipitated

40
Q

common precipitants of respiratory muscle weakness and subsequent myasthenic crisis include … (4)

A

common precipitants of respiratory muscle weakness and subsequent myasthenic crisis include surgery, infections, medications or tapering immunosuppression.

41
Q

Myasthenia gravis - Neck muscles: extensor and flexor muscles can be affected. May get ‘…-… syndrome’ towards end of day.

A

Neck muscles: extensor and flexor muscles can be affected. May get ‘dropped-head syndrome’ towards end of day.

42
Q

Facial muscle weakness in myasthenia gravis

A

Facial muscles: expressionless face. Poor smile or classical ‘myasthenic sneer’ (mid lip rises but outer mouth corners fail to move)

43
Q

Bulbar muscle weakness in myasthenia gravis

A

Bulbar muscles: fatiguable chewing, dysarthria, dysphagia.

44
Q

Ice pack test in myasthenia gravis

A

Refers to the improvement of ptosis in patients with MG after the application of a bag filled with ice to the closed eyelid for one minute. After removal, the extent of ptosis is immediately assessed. There should be a short duration of improvement (< 1 minute). Sensitivity is approximately 80%.

The test relies on the principle that neuromuscular transmission is better at lower muscle temperature. The ice pack test is not diagnostic and instead, supports the diagnosis when suspected.

45
Q

The diagnosis of MG is generally based on .. and ..

A

The diagnosis of MG is generally based on clinical features and serological testing.

46
Q

Diagnosing myasthenia gravis

A

The diagnosis of MG is generally based on clinical features and serological testing.
Muscle weakness with fatiguability and the presence of AChR-Ab are usually enough to support the diagnosis of MG and consider treatment. All patients with suspected MG should be referred to a neurologist for further assessment and initiation of treatment. Patients with severe symptoms or concern about myasthenic crisis need urgent hospital admission.

47
Q

Bedside tests for myasthenia gravis (2)

A

Ice-pack test: discussed above
Edrophonium (tensilon) test: no longer completed in clinical practice. Consisted of an infusion of edrophonium, which is an acetylcholinesterase inhibitor with rapid onset and short duration. Leads to a brief improvement in symptoms in patients with obvious ptosis or ophthalmoplegia. False positive and negatives. Safety concerns due to muscarinic side-effects (e.g. bradycardia, bronchospasm).

48
Q

Edrophonium (tensilon) test: no longer completed in clinical practice. Consisted of an infusion of edrophonium, which is an acetylcholinesterase inhibitor with rapid onset and short duration. Leads to a brief improvement in symptoms in patients with obvious ptosis or ophthalmoplegia. False positive and negatives. Safety concerns due to … side-effects

A

Edrophonium (tensilon) test: no longer completed in clinical practice. Consisted of an infusion of edrophonium, which is an acetylcholinesterase inhibitor with rapid onset and short duration. Leads to a brief improvement in symptoms in patients with obvious ptosis or ophthalmoplegia. False positive and negatives. Safety concerns due to muscarinic side-effects (e.g. bradycardia, bronchospasm).

49
Q

Serological tests for myasthenia gravis

A

AChR-Ab: 90% of generalised, 50% of ocular MG. High specificity (~99%). Rarely, may see false positives in a patient with thymoma without MG.
MuSK and LRP4: completed if AChR-Abs are negative. Typical clinical phenotype.
Others: multiple antibodies against differentiate components of skeletal muscle (Anti-striated muscle antibodies). Strongly linked with thymoma.

50
Q

… (RNS) and electromyography (EMG) can be used to help diagnose MG, especially in seronegative cases.

A

Repetitive nerve stimulation (RNS) and electromyography (EMG) can be used to help diagnose MG, especially in seronegative cases.

51
Q

Repetitive nerve stimulation (RNS) - myasthenia gravis

A

In RNS, an electrode is placed over a region of muscle and the motor nerve to that muscle is stimulated repeatedly at 2-3 Hz around 6-10 times. In MG, with repeated stimulation there is a progressive decline in amplitude suggesting fatiguability. EMG is more sensitive, but more technically difficult. May be used if RNS is negative or where availability allows.

52
Q

electromyography (EMG) - myasthenia gravis

A

In RNS, an electrode is placed over a region of muscle and the motor nerve to that muscle is stimulated repeatedly at 2-3 Hz around 6-10 times. In MG, with repeated stimulation there is a progressive decline in amplitude suggesting fatiguability.

EMG is more sensitive, but more technically difficult. May be used if RNS is negative or where availability allows.

53
Q

All patients with suspected MG, irrespective of clinical or serological subtype need to undergo assessment of the … ..using CT or MRI.

A

All patients with suspected MG, irrespective of clinical or serological subtype need to undergo assessment of the thymus gland using CT or MRI. Both imaging modalities are excellent at identification of a thymoma, but it may be difficult to distinguish between thymoma and hyperplasia. Thymoma is very uncommon in the absence of AChR-Ab or anti-striated muscle antibodies .

54
Q

What tests should be done in someone presenting with myasthenia gravis clinical features?

A

All patients should undergo thyroid function tests because of the strong association with thyroid autoimmune disease. Other tests including a rheumatological screen (e.g. ANA, ENA, CCP, RF) or cerebral imaging (e.g. MRI brain) are guided by the clinical presentation and presence or absence of typical antibodies.

55
Q

The principle initial treatment for MG is …, which is an acetylcholinesterase inhibitor.

A

The principle initial treatment for MG is pyridostigmine, which is an acetylcholinesterase inhibitor.

56
Q

Treatment options for myasthenia gravis

A 
Acetylcholinesterase inhibitors (e.g. pyridostigmine): prevent the hydrolysis of acetylcholine and increases its effect at the NMJ. Usually given as initial therapy. Associated with cholinergic side-effects (secretions, diarrhoea, GI upset, bronchospasm, sweating, urinary incontinence).
Corticosteroids (e.g. prednisolone): immunosuppressive effects. Given if ongoing symptoms despite pyridostigmine. Given as an alternate day strategy and dose increased until symptomatic improvement. Different dose if ocular or generalised.
Immunosuppressants: Azathioprine usually offered first-line. Inhibits purine synthesis. Must check TPMT level before use due to risk of bone marrow suppression. Other options include mycophenolate mofetil, methotrexate, ciclosporin, rituximab (anti-CD 20 monoclonal antibody)
57
Q

Ocular myasthenia - initial therapy, failing to respond, resistant symptoms, relapse guidance

A

Initial therapy: pyridostigmine (usually 15 mg QDS for 2-4 days then slowly uptitrate according to protocol).
If failing to respond: introduce prednisolone at 5 mg alternate days and then increase as per protocol (max 50 mg alternate days). Consider bone and gastric protection as likely long-term use. Counsel on side-effects.
Resistant symptoms, high steroid dose or side-effects: consider immunosuppressant therapy with azathioprine or other agent if contraindication.
Relapses: identify a precipitant, consider restarting or escalating corticosteroids. May need to consider starting or altering immunosuppressant.

58
Q

Ocular myasthenia

Initial therapy: … (usually 15 mg QDS for 2-4 days then slowly uptitrate according to protocol).

A

Ocular myasthenia

Initial therapy: pyridostigmine (usually 15 mg QDS for 2-4 days then slowly uptitrate according to protocol).

59
Q

Ocular myasthenia - If failing to respond to pyridostigmine ?

A

introduce prednisolone at 5 mg alternate days and then increase as per protocol (max 50 mg alternate days). Consider bone and gastric protection as likely long-term use. Counsel on side-effects.

60
Q

Ocular myasthenia - after pyridostigmine + resistant symptoms / high steroid dose or side effects
What next?

A

consider immunosuppressant therapy with azathioprine or other agent if contraindication.

61
Q

Relapses in ocular myasthenia

A

Relapses: identify a precipitant, consider restarting or escalating corticosteroids. May need to consider starting or altering immunosuppressant.

62
Q

Generalised myasthenia initial therapy

A

pyridostigmine (usually 15 mg QDS for 2-4 days then slowly uptitrate according to protocol).

63
Q

Generalised myasthenia - failing to respond to pyridostigmine?

A

introduce prednisolone at 10 mg alternate days and then increase as per protocol (max 100 mg alternate days). Consider bone and gastric protection as likely long-term use. Counsel on side-effects.

64
Q

Generalised myasthenia - resistant symptoms, high steroid dose or side effects (after pyridostigmine and steroids?)

A

consider immunosuppressant therapy with azathioprine or other agent if contraindication.

65
Q

Generalised myasthenia - relapse management

A

Relapses: identify a precipitant, consider restarting or escalating corticosteroids. May need to consider starting or altering immunosuppressant.

66
Q

Patients with evidence of a thymoma should be referred to a thoracic surgeon for consideration of …

A

Patients with evidence of a thymoma should be referred to a thoracic surgeon for consideration of thymectomy. This is usually completed in a centre with access to neurology input and specialist anaesthetic care due to the risk of deterioration peri-procedure. Thymectomy can also be considered in patients without thymoma who are < 45 years old and have positive AChR antibodies.

67
Q

Thymectomy can also be considered in patients without thymoma who are < … years old and have positive AChR antibodies.

A

Thymectomy can also be considered in patients without thymoma who are < 45 years old and have positive AChR antibodies.

68
Q

A myasthenia crisis is defined as a worsening of weakness that requires …

It is important to recognise patients with, or at risk of, a myasthenic crisis because they need urgent admission to hospital and possible referral to the high-dependency unit (HDU) or intensive treatment unit (ITU).

A

A myasthenia crisis is defined as a worsening of weakness that requires respiratory support (e.g. intubation or non-invasive ventilation). Up to 20% of patients will experience a MG crisis within their lifetime.

It is important to recognise patients with, or at risk of, a myasthenic crisis because they need urgent admission to hospital and possible referral to the high-dependency unit (HDU) or intensive treatment unit (ITU).

69
Q

Inpatient management should be considered in any patient with, or at risk of, a myasthenic crisis. This includes those with:

Significant … symptoms
Low …
Respiratory symptoms
Progressive deterioration

A

Inpatient management should be considered in any patient with, or at risk of, a myasthenic crisis. This includes those with:

Significant bulbar symptoms
Low forced vital capacity (FVC)
Respiratory symptoms
Progressive deterioration

70
Q

Inpatient management in myasthenia gravis

A

All inpatients should be assessed by the speech and language team (SALT) and should have regular assessment of their FVC. FVC is main tool for monitoring deterioration in respiratory function. If there are any concerns, patients should be referred to HDU/ITU where they can have closer monitoring of respiratory function and earlier intervention with respiratory support as needed.

71
Q

Forced vital capacity - Measuring FVC should be based on weight and any significant fall should warrant referral to HDU/ITU for closer monitoring, or if significantly low, respiratory support.

Generally, an FVC < … ml/kg should warrant referral to HDU/ITU

A

Generally, an FVC < 30 ml/kg should warrant referral to HDU/ITU

If weight 55 kg: FVC < 1.6L should warrant referral
If weight 90 kg: FVC < 2.7L should warrant referral

72
Q

If the FVC falls below ..-.. mls/kg, then elective intubation should be considered.

A

If the FVC falls below 15-20 mls/kg, then elective intubation should be considered.

73
Q

…: consider if severe respiratory or bulbar symptoms (1-2 g/kg total dose, given over several days). May be repeated if limited initial effect, should be discussed with neurology.

A

IVIG: consider if severe respiratory or bulbar symptoms (1-2 g/kg total dose, given over several days). May be repeated if limited initial effect, should be discussed with neurology.

74
Q

Plasma exchange: considered if poor response to … Removal of patients plasma and replaced with albumin or fresh frozen plasma.

A

Plasma exchange: considered if poor response to IVIG. Removal of patients plasma and replaced with albumin or fresh frozen plasma.

75
Q

Myasthenic crisis management
Corticosteroids: … can be reinstated via NG tube or orally depending on whether intubated. In general, if ventilated, give high dose (e.g. 100 mg alternate days). If not ventilated, can consider standard starting … protocol. May lead to a temporary worsening of symptoms within 5-10 days of starting treatment (less concern if also receiving IVIG).

A

Corticosteroids: prednisolone can be reinstated via NG tube or orally depending on whether intubated. In general, if ventilated, give high dose (e.g. 100 mg alternate days). If not ventilated, can consider standard starting prednisolone protocol. May lead to a temporary worsening of symptoms within 5-10 days of starting treatment (less concern if also receiving IVIG).

76
Q

… should generally be avoided during an acute crisis due to the increase in respiratory secretions and risk of aspiration. Furthermore, excessive use of magnesium sulphate on ITU should be avoided where possible (precipitates worsening symptoms)

A

Pyridostigmine should generally be avoided during an acute crisis due to the increase in respiratory secretions and risk of aspiration. Furthermore, excessive use of magnesium sulphate on ITU should be avoided where possible (precipitates worsening symptoms)

77
Q

Pyridostigmine should generally be avoided during an acute crisis due to the increase in respiratory secretions and risk of aspiration. Furthermore, excessive use of … … on ITU should be avoided where possible (precipitates worsening symptoms)

A

Pyridostigmine should generally be avoided during an acute crisis due to the increase in respiratory secretions and risk of aspiration. Furthermore, excessive use of magnesium sulphate on ITU should be avoided where possible (precipitates worsening symptoms)

78
Q

Precipitating factors for Myasthenic crisis (7)

A 
Warm weather
Surgery
Stress
Infections and intercurrent illness
Co-morbidities
Pregnancy
Medications
79
Q

A number of medications have been recognised to worsen symptoms and may precipitate a myasthenic crisis. It is imperative to try and avoid these medications, where possible, in patients with MG.

A

Antibiotics: aminoglycosides (e.g. gentamicin), ciprofloxacin, clindamycin, erythromycin
Antihypertensives/Antiarrhythmics: beta-blockers, calcium-channel blockers
Neuromuscular blocking agents: atracurium, vecuronium
Many others (e.g. phenytoin, statins, lithium, penicillamine chloroquine, magnesium, prednisolone)

80
Q

With modern treatment mortality from MG is…

A

With modern treatment mortality from MG is 3-4%.

81
Q

MG used to be associated with a high mortality (~40%). Morbidity is largely related to respiratory and … muscle symptoms that may be associated with respiratory failure and aspiration.

A

MG used to be associated with a high mortality (~40%). Morbidity is largely related to respiratory and bulbar muscle symptoms that may be associated with respiratory failure and aspiration.

82
Q

Informally, there are three main stages of MG:

A

Informally, there are three main stages of MG:

83
Q

Early in the disease, patients usually have fluctuant muscle weakness with long periods (hours/days/week) being symptom free. As the disease progresses, symptoms may worsen and become more persistent. The clinical manifestations generally peak within three years of onset.

Informally, there are three main stages of MG:

A 
Stage one (active): fluctuating muscle weakness with most severe clinical features. Majority of crises occur in this phase.
Stage two (stable): persistent, but stable symptoms. Serious exacerbations may develop due to infection, medications, or altering treatment. 
Stage three (remission): a minority of patients may develop complete remission without need for treatment.

Neurology (32 decks)

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