What is a floppy baby?

 

The term 'floppy baby' refers to neonatal hypotonia, which is a reduced resistance to passive movement.  These babies can present with head lag, truncal instability, feeding and breathing difficulties, or they may just 'feel' different from other babies when handled.

They can present significant diagnostic and therapeutic challenges. 

How do you recognise a floppy baby?

 

There are several important manoeuvres which help you assess a baby's tone (illustrated):

  1. Pulling to sit from supine.  Hold the baby's hands and gently pull them up into the sitting position.  A healthy newborn will support their head in the same plane as the body as they are pulled up.  A floppy baby will show head lag, with their head falling back behind their body.
  2. Ventral suspension.  Suspend the baby in the prone position with one or both of your hands supporting them around their middle.  A normal newborn will maintain a straight back with flexed arms and legs, and head less than 45 degrees to the horizontal.  A hypotonic baby will have a rounded back, extended arms and legs, and head further down.
  3. Holding upright.  Support the baby in the upright position with your hands on the axillae.  The floppy baby will seem to slip between your hands, due to reduced tone in the shoulder girdle.
pulling from supine

ventral suspensionholding upright

The key to the diagnosis

 

Approaching a floppy baby can feel very intimidating, as there are literally thousands of differential diagnoses and potential investigations.  However, it is possible to take a straightforward and logical approach.  The key is to decide whether the cause is general (systemic), central or peripheral. 

Any baby that is generally unwell, for example with sepsis or heart failure, can become hypotonic.  Physiological hypotonia is seen in premature babies.  General causes should be easily identified from the history.  It is the central (neurological) and peripheral (neuromuscular) causes which often lead to confusion.  The easiest way to differentiate between these is by asking yourself:

Is the baby weak?

    In central causes the baby will not be weak.  They have upper motor neuron signs, with truncal hypotonia, but normal strength peripherally, and normal antigravity movements of the limbs.  There may be peripheral hypertonia, brisk reflexes, and clonus.  There may be other signs of central nervous system dysfunction including seizures, microcephaly and reduced visual interaction.

    In peripheral causes the baby will be weak.  They will have lower motor neuron signs, be globally hypotonic, with loss of antigravity movements of the limbs.  Reflexes are reduced or absent.  These babies are often cognitively normal, so tend to appear alert and visually interactive. 

     

    Underlying diagnoses

     

    Central

    Central nervous system problems are the cause of the majority (60-80%) of cases of neonatal hypotonia.  Specific diagnoses to be considered include:

    • Hypoxic ischaemic encephalopathy
    • Intracranial haemorrhage
    • Genetic abnormalities (e.g. Prader Willi syndrome)
    • Cerebral malformations
    • Congenital infection (TORCH)
    • Metabolic disorders (aminoacidurias, organic acidurias, peroxisomal disorders)

     

    Peripheral

    Peripheral causes are detailed in the 'neuromuscular disorders' section of the fastbleep paediatric notes.

     

    A summary of the key findings in central and peripheral causes, along with some common examples is given in the table below.

     

    summary table

    Assessment

     

    With the above approach in mind, you can now confidently gather information in a directed way.

     

    History 

     

    Pregnancy

    • Drug or infection exposure
    • Maternal disease
    • Reduced fetal movements (suggests severe peripheral cause for hypotonia with onset in utero)
    • Polyhydramnios (due to a poor swallow in a weak fetus)

     

      Delivery

      • Presentation (a weak fetus is less able to manoeuvre into the correct position)
      • Method of delivery & indication if assisted
      • Need for resuscitation
      • Apgar scores
      • Birth weight and head circumference centiles

       

        Progress since delivery

        • Admission to the neonatal unit
        • Respiratory problems
        • Method of feeding, feeding difficulties
        • Level of alertness
        • Level of spontanoeus activity
        • Quality of the cry
        • Progress of the hypotonia: is it progressive?

         

          Family history

          • Compose a full family tree
          • Illness in family, especially neuromuscular and in mother
          • Consanguinity
          • Stillbirths

           

          Examination

           

          Perform a full examination (as you would for a '1st day check'), particularly looking for:

          • micro/macrocephaly
          • tone using ventral suspension, pulling to sit from supine, holding upright, position at rest
          • is the hypotonia global or just truncal
          • tone and reflexes in limbs
          • primitive reflexes (grasp, Moro, sucking)
          • visual alertness
          • fasciculation
          • arthrogryposis (fixed joint deformities from reduced fetal movement)
          • hepatosplenomegaly (metabolic disorders)
          • examine the mother for signs of myotonic dystrophy - can she bury her eyelashes, can she release her clenched fist quickly (shake hands)
          • examine the mother for signs of myasthenia gravis - fatigueabililty on one minute upgaze

           

          Investigations

          Focus your investigations according to whether have found signs of a central or peripheral disorder in the history and examination.  There is an almost limitless number of tests available, but those with the highest yield are shown in the table.  Expert advice should be sought before performing any additional tests.

           

          investigations

          Management & Prognosis

           

          Specific treatment will vary depending on the underlying cause.  Supportive management is usually necessary, and a holistic approach should be taken.

          • feeding support (nasogastric tube, gastrostomy)
          • respiratory support (oxygen, CPAP, ventilation, physiotherapy)
          • physiotherapy (prevention of contractures, pressure sores)
          • speech and language support (assessing swallow)
          • dietetic support (optimising nutrition)
          • antiepileptic medication
          • support for family (social, psychological, financial)
          • palliative care (for symptom control as well as end of life care)

           

          The prognosis is also dependant on the underlying diagnosis.  However, many of these conditions have a poor prognosis with no specific therapies available.   Genetic counselling is important, to aid parents in planning future pregnancies.

           

          References

          Dubowitz V. The floppy infant. JB Lippincott Company, Philadelphia 1980

          Forsyth R, Newton R. Oxford Specialist Handbook in Paediatric Neurology.  Oxford University Press, Oxford 2007

          Photographs and tables by the author

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