Floppy infant syndrome is also called as Hypotonia or Rag-doll syndrome. It is a medical term for low muscle tone. If an infant has this condition and when you lift that infant with your hands, the baby appears firm (lacking strength) – just like a rag doll. Therefore, the name – floppy infant syndrome. Hypotonia or floppiness is a common neurological problem in infancy. Poor muscle tone that varies in severity and duration tends to signal a problem with the brain, spinal cord, nerves, or muscles.

Floppy Infant Syndrome Causes

A wide range of disorders including central nervous system and peripheral nervous system disorders can cause hypotonia, but CNS disorders are the common cause of FIS than neuromuscular disorders (Infantile botulism, congenital myasthenia, Transient acquired neonatal myasthenia, Aminoglycoside toxicity, magnesium toxicity and hyperkalaemia).

Floppy Infant Syndrome Symptoms

Healthy babies are born with healthy muscle tone – which allows them to move their little limbs. They flex their muscles to ease their limbs’ movement. Babies who have hypotonia lack muscle tone and strength – and therefore, lack strong arms and legs movements.

The other symptoms of FIS

  • Hyperextensibility of joints
  • Abnormal postures
  • Fisting of the hands
  • Lack of head control
  • Abnormalities of brain function
  • Depressed level of consciousness
  • Dysmorphic features
  • Scissoring on vertical suspension
  • Feeding difficulties
  • Developmental Delays
  • Social and Cognitive impairment
  • Open mouth with a tented upper lip
  • Lack of facial expression

Typical Signs

Frog-like posture, rag-doll appearance, the jug-handle posture of arms, slipping through hands disposition when held under the arms.


A Paediatric neurologist performs clinical examination – which is important – especially during the neonate period. The doctor will next go for investigating and diagnosing the underlying cause of FIS – which is the next crucial aspect. Irrespective of whether the cause of FIS involves the central or peripheral nervous system, during the clinical examination, the doctor looks for the presence of some specific signs and symptoms including frog-leg posture, a feeling of the child slipping through the hands when held under the arms, rag-doll posture, head lacking control and pull-to-sit manoeuvre and so on.

Experienced paediatric neurologists can detect hypotonia within few minutes after birth. If a paediatrician suspects any abnormality, he or she will recommend paediatric neurologist to clinically examine the child. Paediatric neurologists check muscle tone at a fixed time interval after birth. Sometimes hypotonia shows up a bit later, but it will usually be noticeable by 6 months of age. Most of the cases of hypotonia can be successfully diagnosed with physical and clinical examination, proper history – maternal and family history, neurological examination and certain diagnostic tests.

A few of such tests include MRI or CT scan of the brain, EEG (Electroencephalogram), EMG (Electromyography), Muscle biopsy, spinal tap and genetic tests.


During early infancy, diagnosing hypotonia can be relatively straightforward, but determining the hidden (underlying) cause can be sometimes unsuccessful or difficult. However, considering the long-term consequences and effects on a child’s development in later life, the detection of the underlying cause is crucial. For a known cause, treatment is specific, but mostly the principal treatment for hypotonia of neurological or idiopathic cause, physical or occupational therapy can help the child build stronger muscles and better coordination.

Bottom Line

General physicians and paediatricians may find it difficult to diagnose floppy infant – as it is a diagnostic challenge for them. The reason – Floppy Infant Syndrome is not a specific neurological disorder – it is rather a potential manifestation of several disorders or different types of the central nervous system or peripheral nervous system disorders or neuromuscular disorders. For instance, a child may be presented with hypotonia symptoms – which could be due to endocrinopathies, genetic disorders, myopathies, central or peripheral nervous system abnormalities or could be due to metabolic disorders or acute or chronic illnesses. In such a challenging scenario, paediatric neurologists approach the case with thorough due diligence paying attention to immense details including the history of the child, clinical examination and associated symptoms. This will help in the precise diagnosis of the disorder.