Spinal muscular atrophy Flashcards
What is spinal muscular atrophy?
A condition characterised by slowly progressive muscle weakness and atrophy of the limb muscles associated with motor neurone loss in the spinal cord
Describe the genetics of spinal muscular atrophy
Autosomal recessive mutation of the SMN1 gene
Describe the pathophysiology of spinal muscular atrophy
Loss of anterior horn cells
What are some symptoms of spinal muscular atrophy?
- Muscle weakness and wasting
- Proximal skeletal muscles
- Respiratory muscles
What are some clinical signs of spinal muscular atrophy?
Hypotonia
Flaccid weakness
Reduced/abscent tendon reflexes,
Normal/absent plantar reflexes
Muscle fasciculation
Muscle atrophy
What are the 4 types of SMA dependant on history?
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
What investigations are required in SMA?
- Creatine kinase - normal or slightly raised
- Genetic testing
- Electrophysiology testing shows diminished nerve signals
- Muscle biopsy - muscle fibre atrophy
What new treatment has been developed for treatment of SMA?
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