Floppy Infant

Initial approach

• Floppy neonate → History and physical examination
• Distinguish two clinical pictures (central vs peripheral)

Central pattern — hypotonia with abnormal consciousness

• Hypotonia with abnormal consciousness, seizures, apnea, abnormal posturing, and feeding difficulties
• → CT/MRI, Screening for IEM, Septic screen, CSF analysis, Karyotype
• → Perinatal asphyxia, cerebral malformations, IEM, sepsis, chromosomal disorders

Peripheral pattern — hypotonia with preserved alertness

• Hypotonia, weakness, alert look, fasciculations, absent or reduced tendon reflexes
• → Muscle weakness in mother?

Muscle weakness in mother — Yes

• Maternal myotonia?
• Yes: Myotonic dystrophy
• No: History of myasthenia in mother → Transient myasthenia gravis - AchR Ab and edrophonium test

Muscle weakness in mother — No → Creatine kinase

• Creatine kinase High → Congenital muscular dystrophy
• Creatine kinase Normal → DNA testing for spinal muscular atrophy (SMN)
• DNA testing YES → SMA
• DNA testing Negative → EMG and NCS

EMG and NCS — Myopathic

• Myopathic → Congenital myopathies → confirm by muscle biopsy

EMG and NCS — Neuropathic

• Neuropathic → NCV
• NCV Normal → SMA
• NCV Reduced → Peripheral Neuropathy → Confirm by nerve biopsy

EMG and NCS — Neuromuscular transmission defect

• Neuromuscular transmission defect → Transient myasthenia gravis, congenital myasthenia syndrome