Floppy infant syndrome and muscle disorders

Question 1

Spinal Muscular Dystrophy

Answer 1

progressive deterioration of anterior horn cells
hereditary - autosomal recessive, 2 genes involved chromosome 5q
fasciculations
type 1 = Werdnig Hoffman
- can’t lift head, can’t sit, bright/ interacts well
- proximal weakness
- reflexes absent
- onset in utero or first few months life
- prognosis poor rarely survives second year

type 2 - Intermediate

• delay gross motor development
• can sit but can’t stand without support
• average or > intelligence
• reflexes reduced
• onset 3-15 months
• prognosis depend involvement resp system

type 3 - Krugelberg Welander

• least severe
• initial milestones normal but walks late
• onset after 18 months
• most reach adulthood - very gradual decline

Question 2

Duchenne’s Muscular Dystrophy

Answer 2

x linked recessive inheritance - affects boys
incidence of 1 in 5000
onset around 18 months - delay walking
abnormal gait, frequent falls, difficulty climbing stairs, toe walking, lordotic posture
progressive weakness - Gower’s signs - sign of proximal weakness
pseudo hypertrophy calves

lose ability to walk in teens 
scoliosis spine 
respiratory problems 
associated with cardiomyopathy and mild intellectual impairment 
death due respiratory failure in teens 

Dx

• grossly elevated CK
• deletions in dystrophin gene typical - also point mutations
• muscle biopsy if genetics negative
• carrier detection via CK values or gene studies

Question 3

What tests should you use to check for a floppy infant?

Answer 3

Ventral suspension

Vertical suspension

Question 4

Name causes of hypotonic infant according to features

Answer 4

Sick child
- malnutrition
- cardiac failure
- acute illness
Dysmorphic
- Down
- Prader Willi
- storage disorder
Reflexes incr 
- CP
Reflexes decr 
- mm
- nn
- NM junction
Fasciculations with bright face
- SMA
Not weak, delayed, normal reflexes
- hyperlaxity
- endocrine