Spinal muscular atrophy Flashcards

1
Q

What is spinal muscular atrophy?

A

A condition characterised by slowly progressive muscle weakness and atrophy of the limb muscles associated with motor neurone loss in the spinal cord

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2
Q

Describe the genetics of spinal muscular atrophy

A

Autosomal recessive mutation of the SMN1 gene

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3
Q

Describe the pathophysiology of spinal muscular atrophy

A

Loss of anterior horn cells

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4
Q

What are some symptoms of spinal muscular atrophy?

A
  • Muscle weakness and wasting
    • Proximal skeletal muscles
    • Respiratory muscles
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5
Q

What are some clinical signs of spinal muscular atrophy?

A

Hypotonia
Flaccid weakness
Reduced/abscent tendon reflexes,
Normal/absent plantar reflexes
Muscle fasciculation
Muscle atrophy

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6
Q

What are the 4 types of SMA dependant on history?

A

Type 1 - Never sits, median age of death or ventilation - 13.5 months

Type 2 - Never walks independently

Type 3 - Childhood onset

Type 4 - Adult onset

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7
Q

What investigations are required in SMA?

A
  • Creatine kinase - normal or slightly raised
  • Genetic testing
  • Electrophysiology testing shows diminished nerve signals
  • Muscle biopsy - muscle fibre atrophy
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8
Q

What new treatment has been developed for treatment of SMA?

A

Drugs that perform correction of SM1 deficiency by altering splicing of SMN2 mRNA

Effective in preventing progression but do not reverse the loss of anterior horn cells - disability can be prevented by starting treatment at birth

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9
Q
A
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