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AIP: Acute weakness > Periodic paralysis > Flashcards

Periodic paralysis Flashcards

1
Q

What is familial periodic paralysis?

A

rare inherited condition with considerable variation in penetrance characterised by episodes of flaccid paralysis with loss of deep tendon reflexes and failure of muscle to respond to electrical stimulation

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2
Q

What is the inheritance pattern of familial periodic paralysis?

A

autosomal dominant

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3
Q

What type of paralysis is seen with familial periodic paralysis?

A

Episodes of flaccid paralysis

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4
Q

What are 3 clinical features typically seen in all types of familial periodic paralysis?

A
  1. Episodes of flaccid paralysis
  2. Loss of deep tendon reflexes
  3. Failure of muscle to respond to electrical stimulation
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5
Q

What are the 4 forms of familial periodic paralysis?

A
  1. Hypokalaemic
  2. Hyperkalaemic
  3. Thyrotoxic
  4. Andersen-Tawil syndrome
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6
Q

How is a diagnosis of familial periodic paralysis made?

A

indicated by history, confirmed by provoking an episode e.g. giving dextrose and insulin to cause hypokalaemia or potassium chloride to cause hyperkalaemia

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7
Q

What differentiates the pathophysiology of each form of familial periodic paralysis?

A

each form involves a different gene and electrolyte channel

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8
Q

What is the pathophysiology of the hypokalaemic form of familial periodic paralysis? 2 types

A
  1. 70% of affected people have mutation in alpha-subunit of the voltage-sensitive muscle calcium channel gene on chromosome 1q (HypoPP type I)
  2. in some families, the mutation is the alpha-subunit of the sodium channel gene on chromosome 7 (HypoPP type II)
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9
Q

What is the most common form of familial periodic paralysis?

A

Hypokalaemic form (although still rare - prevalence 1/ 100 000)

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10
Q

What is the pathophysiology of the hyperkalaemic form of familial periodic paralysis?

A

mutations in the gene that encodes the alpha-subunit of the skeletal muscle sodium channel (SCN4A)

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11
Q

What is the pathophysiology of the thyrotoxic form of familail periodic paralysis?

A

mutations and affected electrolyte channels are unknown but this form usually involves hypokalaemia and is associated with symptoms of thyrotoxicosis

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12
Q

In which patient group is the incidence of the thyrotoxic form of FPP most common?

A

Asian men

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13
Q

What is the pathophysiology of Andersen-Tawil syndrome?

A

due to an autosomal dominant defect of the inward-rectifying potassium chanel; patients can have a high, low or normal serum potassium level

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14
Q

At what age do episodes of hypokalaemic periodic paralysis typically begin?

A

usually before age 16

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15
Q

How does hypokalaemic periodic paralysis often present?

A

the day after vigorous exercise, patient often awakens with weakness, which may be mild and limited to certain muscle groups or may affect all 4 limbs

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16
Q

What are 6 things which can precipitate hypokalaemic periodic paralysis episodes?

A
  1. Vigorous exercise on preceding day
  2. Carbohydrate-rich meals
  3. Emotional stress
  4. Physical stress
  5. Alcohol ingestion
  6. Cold exposure
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17
Q

What are 3 groups of muscles which are spared in hypokalaemic periodic paralysis?

A
  1. Ocular
  2. Bulbar
  3. Respiratory muscles
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18
Q

Is consciousness altered in hypokalaemic periodic paralysis?

A

no

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19
Q

What are the findings on blood and urine tests in hypokalaemic periodic paralysis?

A

serum and urine potassium are decreased

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20
Q

How long may weakness last in hypokalaemic periodic paralysis?

A

up to 24 h

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21
Q

How does the presentation of hyperkalaemic periodic paralysis compare with hypokalaemic PP?

A

episodes often begin at an earlier age and usually are shorter, more frequent, and less severe

22
Q

What are 3 things that precipitate episodes of hyperkalaemic periodic paralysis?

A
  1. Rest after exercise
  2. Exercise after meals
  3. Fasting
23
Q

What feature, alongside paralysis, is a common feature of hyperkalaemic periodic paralysis and how may this present?

A

myotonia - delayed relaxation after muscle contraction

eyelid myotonia may be the only symptom

24
Q

How long do episodes of thyrotoxic periodic paralysis last?

A

episodes last hours to days

25
Q

What are 3 things that can precipitate thyrotoxic periodic paralysis?

A
  1. Exercise
  2. Stress
  3. Carbohydrate load
26
Q

What are 8 features that may be present with thyrotoxic periodic paralysis?

A

Symptoms of thyrotoxicosis:

  1. Anxiety
  2. Emotional lability
  3. Weakness
  4. Tremor
  5. Palpitations
  6. Heat intolerance
  7. Increased perspiration
  8. Weight loss
27
Q

Within what time in relation to each other may symptoms of thyrotoxicosis and periodic paralysis occur in thyrotoxic periodic paralysis?

A

clinical features of hyperthyroidism often precede onset of periodic paralysis by months or years; however, features have been noted to occur at same time as periodic paralysis or after development of it

28
Q

At what age do episodes of Andersen-Tawil syndrome usually begin?

A

before age 20

29
Q

What is the clinical triad present in Andersen-Tawil syndrome?

A
  1. Periodic paralysis
  2. Prolonged QT interval and ventricular arrhythmias
  3. Dysmorphic physical features

all or some may be present

30
Q

What are 9 of the dysmorphic physical features which may be present in Andersen-Tawil syndrome?

A
  1. Short stature
  2. High-arched palate
  3. Low-set ears
  4. Broad nose
  5. Micrognathia
  6. Hypertelorism (increased distance between eyes)
  7. Clinodactyly of fingers
  8. Short index fingers
  9. Syndactyly of toes
31
Q

What precipitates episode of paralysis in Andersen-Tawil syndrome?

A

rest after exercise

32
Q

How long do episodes of periodic paralysis last in Andersen-Tawil syndrome and how frequently may these occur?

A

may last for days, occur monthly

33
Q

What are the 3 key things which a diagnosis of periodic paralysis is based upon?

A
  1. Clinical evaluation
  2. Serum potassium level during symptoms
  3. Sometimes provocative testing
34
Q

What is the best diagnostic indicator of periodic paralysis?

A

history of typical episodes

35
Q

When might serum potassium be abnormal in periodic paralysis?

A

if measured during an episode

36
Q

How can episodes of hypokalaemic periodic paralysis be triggered?

A

by giving dextrose and insulin

37
Q

How can episodes of hyperkalaemic periodic paralysis be triggered to help diagnosis?

A

giving potassium chloride

38
Q

Who are the only people who should attempt provocative testing in periodic paralysis and why?

A

only experienced physicians - respiratory paralysis or cardiac conduction abnormalities may occur

39
Q

What can be used to aid the diagnosis of the hyperkalaemic form of periodic paralysis?

A

clinical findings and/or identification of a heterozygous pathogenic variant in the alpha-subunit of the skeletal muscle sodium channel

40
Q

What is the acute management of hypokalaemic periodic paralysis?

A

potassium chloride 2 to 10 g in an unsweetened oral solution or giving potassium chloride IV

41
Q

What 5 aspects of prevention of hypokalaemic periodic paralysis episodes?

A
  1. Low-carbohydrate diet
  2. Low-sodium diet
  3. Avoiding strenuous activity
  4. Avoiding alcohol after periods of rest
  5. Acetazolamide 250mg PO twice a day
42
Q

What are 2 aspects of the management mild paralysis caused by hyerpkalaemic periodic paralysis?

A

light exercise and 2g/kg oral carbohyrate load

43
Q

What are 3 drugs which may be required to treat established episodes of hyperkalaemic periodic paralysis?

A
  1. Thiazides
  2. Acetazolamide
  3. Inhaled beta-agonists (e.g. salbutamol)
44
Q

What are 2 drugs that can be used to treat severe episodes of hyperkalaemic periodic paralysis?

A
  1. Calcium gluconate
  2. Insulin and dextrose IV
45
Q

What are 4 forms of preventions of hyperkalaemic periodic paralysis episodes?

A
  1. Regularly ingesting carbohydrate-rich, low-potassium meals
  2. Avoiding fasting
  3. Avoiding strenuous activity after meals
  4. Avoiding cold exposure
46
Q

What is the management of acute episodes of thyrotoxic periodic paralysis?

A

give potassium chloride, and serum potassium levels closely monitored

47
Q

What are 2 ways to prevent episodes of thyrotoxic periodic paralysis?

A
  1. Maintaining a euthyroid state and
  2. Giving beta blockers e.g. propranolol
48
Q

What are 2 ways to prevent episodes of paralysis due to Andersen-Tawil syndrome?

A
  1. Tightly controlled levels of exercise of activity
  2. Carbonic anhydrase inhibitor e.g. acetazolamide
49
Q

What is the major complication of Andersen-Tawil syndrome?

A

sudden death resulting from cardiac arrhythmias

50
Q

What intervention may be required in Andersen-Tawil syndrome due to the risk of sudden death from cardiac arrhythmias?

A

cardiac pacemaker or implantable cardioverter-defibrillator may be required to control cardiac smypomts

AIP: Acute weakness (18 decks)

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