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Neurology > Spinal muscular atrophy (NMD) > Flashcards

Spinal muscular atrophy (NMD) Flashcards

1
Q

Describe spinal muscular atrophy

A
  1. Genetic condition causing progressive weakning of the muscles and mobility problems
  2. Due to degeneration of alpha motor neurones in the spinal cord and brain stem
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2
Q

What is the incidence of spinal muscular atrophy?

A

1/6,000 to 1/10,000

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3
Q

What is the prevalence of SMA?

A

1 in 100,000

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4
Q

Describe the aetiology of SMA (3)

A
  1. Autosomal recessive mutations in a single gene locus on the short arm of chromosome 5
  2. Causing a homozygous deletion
  3. Homozygous mutation of the SMN1 gene, testing generally shows absence of exon 7
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5
Q

Describe the inheritance patterns of SMA (2)

A
  1. Usually as an autosomal recessive trait

2. Two genes are required, one from each parent

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6
Q

What is the classification of SMA? (5)

A
  1. Type 1 SMA (young babies)
  2. Type 2 SMA (older babies and toddlers)
  3. Type 3 SMA (children and young adults)
  4. Type 4 SMA (adults)
  5. Other types
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7
Q

Describe the symptoms of Type 1 SMA (3)

A
  1. Very weak, floppy arms and legs (hypotonia)
  2. Problems eating, moving, breathing and swallowing
  3. Unable to raise head or sit without support
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8
Q

Describe the symptoms of SMA 2 (5)

A
  1. May sit up without support but cannot stand or walk
  2. Weak arms or legs
  3. Tremors in hands/fingers
  4. Joint problems eg. socliosis
  5. Weak breathing muscles and difficulty coughing
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9
Q

Describe the onset of Type 1 SMA

A

Show symptoms within first 6 months

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10
Q

Describe the prognosis of Type 1 SMA

A

Usually die within few years, usually due to respiratory problems

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11
Q

Describe the onset of Type 2 SMA

A

Symptoms show between 7-18 months

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12
Q

Describe the prognosis of Type 2 SMA (2)

A
  1. Usually less severe than Type 1

2. Can shorten life expectancy but most survive to adulthood

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13
Q

Describe the onset of Type 3 SMA (2)

A
  1. Symptoms after 18 months

2. Very variable - sometimes not until late childhood

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14
Q

Describe the symptoms of Type 3 SMA (4)

A
  1. Able to stand and walk without support but difficulty getting up from sitting position
  2. Balance problems, difficulty running and climbing stairs
  3. Tremors in fingers
  4. Walking gradually gets harder and may lose ability to walk
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15
Q

Describe the prognosis of Type 3 SMA (2)

A
  1. Doesn’t usually affect life expectancy

2. May lose ability to walk

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16
Q

Describe the onset of Type 4 SMA

A

Usually begins early adulthood

17
Q

Describe the symptoms of Type 4 SMA (3)

A
  1. Weakness in hands and feet
  2. Difficulty walking
  3. Shaking and switching muscles
18
Q

Describe the prognosis of Type 4 SMA

A

Gradually progresses over time but doesn’t usually affect breathing, swallowing or life expectency

19
Q

Give 3 other types of SMA

A
  1. Spinal muscular atrophy with respiratory distress (SMARD)
  2. Kennedy’s disease or spinobulbar muscular atrophy
  3. Distal spinal muscular atrophy (DSMA)
20
Q

Describe spinal muscular atrophy with respiratory distress (SMARD)

A

Type of SMA usually diagnosed during first year and can cause serious breathing problems

21
Q

Describe Kennedy’s disease/spinobulbar muscular atrophy (4)

A
  1. Rare type of SMA
  2. Only affects men
  3. Starts in middle age
  4. Doesn’t usually impact life expectancy
22
Q

Describe distal spinal muscular atrophy (DSMA)

A
  1. Type of SMA that mainly affects hands, feet, lower arms and lower legs
23
Q

Summarise the diagnosis of SMA

A
  1. Family history
  2. Electromyography
  3. Blood tests
  4. Amniocentesis
  5. Muscle biopsy
24
Q

What does electromyography find in SMA?

A

Conduction is normal but affected muscles (which are often clinically unaffected) are denervated

25
Q

Why is a muscle biopsy sometimes done? (2)

A
  1. Exclude treatable causes

2. Determine whether the cause is fatal

26
Q

Describe the overall prognosis of SMA (3)

A
  1. Depends on the type
  2. Some may require a wheelchair
  3. Life expectancy may be shortened
27
Q

Describe the treatment of SMA

A
  1. Physio and occupational therapy
  2. Braces and assistive devices
  3. Nusinersen
28
Q

What is nusinersen?

A

New drug that may slightly improve muscle movement

Neurology (17 decks)

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