Neurology - Spinal Muscular Atrophy

Question 1

What is spinal muscular atrophy?

Answer 1

Rare autosomal recessive condition

Causes progressive loss of motor neurones leading to progressive muscle weakness

Question 2

What does SMA affect?

Answer 2

Lower motor neurones in spinal cord

Causes lower motor neurone signs

Question 3

What are lower motor neurone signs?

Answer 3

• Fasciculations
• Reduced muscle bulk
• Reduced tone
• Reduced power
• Reduced or absent reflexes

Question 4

What are the different categories of SMA?

Answer 4

Type 1
Onset in first few months
Death within 2 years

Type 2
Onset within first 18 months
Most common
Most never walk but survive to adulthood

Type 3
Onset after first year of life
Walk without support, eventually lose that ability

Respiratory muscles less affected
Life expectancy close to normal

Type 4
Onset in 20s
Retain ability to walk short distances
Need wheelchair for mobility

Everyday tasks lead to significant fatigue

Respiratory muscles and life expectancy not affected

Question 5

How is SMA managed?

Answer 5

MDT, supportive management

Physiotherapy
Maximises strength in muscles
Retains respiratory functions
Splints, braces and wheelchairs used to maximise function

Respiratory support
NIV particulary in sleep

SMA type 1 may need tracheostomy with mechanical ventilation, dramatically extends life

Percutaneous endoscopic gastrostomy
Feeding when weak swallows make swallowing unsafe