1. Neonatal Hypotonia Clinical Approach To Floppy Baby
Osama Naga, M.D.,
PGY2
7/23/09

2. Neonatal Hypotonia Central Causes Cerebral palsy
Hypoxic ischemic encephalopathy
Intracranial hemorrhage
Cerebral malformations
Chromosomal abnormalities (e.g.Trisomy 21, Prader-Willi syndrome)
Congenital infection TORCH
Acquired infections
Peroxisomal disorders
Drug effects (e.g. benzodiazepines)
Central cause are the most common causes of hypotonia

3. Neonatal Hypotonia Spinal cord
Birth trauma (especially Breech delivery)
Syringomyelia

4. Neonatal Hypotonia Anterior Horn Cell Spinal Muscular Atrophy
Traumatic myelopathy

5. Neonatal Hypotonia Neuromuscular junction Congenital myasthenia gravis
Transient acquired neonatal myasthenia
Infantile botulism

6. Neonatal Hypotonia Muscle
Muscular dystrophies (congenital myotonic dystrophy)
Congenital myopathies (e.g. central core disease)

7. Neonatal Hypotonia Peripheral nerves
Hereditary sensory motor neuropathies
Charcot-Marie-Tooth disease

8. Neonatal Hypotonia Metabolic myopathies Acid maltase deficiency
Carnitine deficiency
Cytochrome-c-oxidase deficiency

9. Neonatal Hypotonia History Any significant family history
Affected parents
Siblings
Consanguinity
Stillbirths
Childhood deaths

10. Neonatal Hypotonia History Maternal disease
Diabetes
Epilepsy
Myotonic dystrophy
Pregnancy and delivery history
Drug or teratogen exposure
Decreased fetal movements
Abnormal presentation
Polyhydramnios/ oligohydramnios

11. Neonatal Hypotonia History Apgar scores Resuscitation requirements
Cord gases

12. Neonatal Hypotonia History History since delivery Respiratory effort
Ability to feed
Level of alertness
Level of spontaneous activity
Character of cry

13. Neonatal Hypotonia Identification of hypotonia
Holding the infant under the arms
The legs will be extended
Decreased tone of the shoulder girdle allows the infant to slip through the examiner's hands

14. Neonatal Hypotonia Identification of hypotonia
Holding the infant in horizontal suspension
The back hangs over the examiner's hand, and the limbs and head hang loosely
Passive extension of the legs at the knees no resistance is met
Pulling the infant from the supine to sitting position the head lags and continues to lag when the sitting position is reached

15. Neonatal Hypotonia Physical Examination Central Normal strength
Normal or increased DTRs
May be Seizure
May be dysmorphic features

16. Neonatal Hypotonia Physical Examination Anterior horn cells
Generalized weakness
Decreased/ absent DTRs
Fasciculations
Often described as alert

17. Neonatal Hypotonia Physical Examination Nerve
Weakness, distal>proximal
Decreased/ Absent DTRs
+/- fasciculations

18. Neonatal Hypotonia Physical Examination Neuromuscular Junction
Weakness, face/ eyes/ bulbar
Normal DTRs
No fasciculations

19. Neonatal Hypotonia Physical Examination Muscles
Weakness, proximal>distal
Decreased DTRs

20. Neonatal Hypotonia Physical Examination Clues and Pitfalls
Profound central hypotonia may have absent DTR
Absent DTR in the first few DOL would not rule out a central cause for the hypotonia

21. Neonatal Hypotonia Physical Examination Clues and Pitfalls
Presence of profound weakness and hypotonia suggest:
Disorder of the lower motor neuron
A sign of this may be a weak cry
Weakness is uncommon in central hypotonia except in the acute stages

22. Neonatal Hypotonia Physical Examination Clues and Pitfalls
Arthrogryposis (the fixation of joints at birth)
Associated with:
Neonatal hypotonia
More commonly with lower motor neuron unit
Multisystem abnormalities

23. Neonatal Hypotonia Physical Examination Clues Hepatosplenomegaly
Storage disorders
Congenital infections
Renal cysts
High forehead
Wide fontanelles
Zellweger’s syndrome

24. Neonatal Hypotonia Physical Examination Clues Abnormal odor
Metabolic disorders
Hypopigmentation, undesceded testes
Prader Willi
Hepatomegaly
Retinitis pigmentosa
Neonatal adrenoleukodystrophy

25. Neonatal Hypotonia Physical Examination Clues
Examination of the mother
Congenital myotonic dystrophy
Myasthenia gravis

26. Neonatal Hypotonia Investigation History and examination
Hypotonia and a degree of  strength
Central cause is most likely
Hypotonic and weak
Peripheral cause is possible
Early review by the neurology service is warranted

27. Neonatal Hypotonia Investigation Central Causes Neuroimaging
Ultrasound scan in the first instance
MRI for structural abnormality
EEG: if seizures suspected

28. Neonatal Hypotonia Investigation Central Causes
Genetics review if any dysmorphic features present
Karyotype (if dysmorphic features)
TORCH screen
DNA methylation studies or FISH for Prader-Willi syndrome (if clinically indicated after a genetics review)
Metabolic work up

29. Neonatal Hypotonia Investigation Peripheral causes
Neurology services review
Molecular genetics – CTG repeats, deletions in SMN gene

30. Neonatal Hypotonia Investigation Peripheral causes
Creatine kinase: If elevated in an early sample, repeat after a few days.
Nerve conduction studies
Muscle biopsy
Depending on clinical situation, may be delayed until around 6 months of age as neonatal results are difficult to interpret
(levels need to be interpreted with caution in the newborn, as levels tend to be high at birth and increase in the first 24 hours, they also increase with acidosis). 

31. References
1-Fenichel GM. Neonatal Neurology 3rd edition. Churchill Livingston Inc. 1990
2-Paro-Panjan D, Neubauer D. Congenital hypotonia: is there an algorithm? Journal of Child Neurology; Jun2004, Vol.19 (6):
3-Prasad AN, Prasad C. The floppy infant: contribution of genetic and metabolic disorders. Brain and Development; Oct 2003, Vol.25(7):