patient with floppy infant

Causes of Floppy Infant

  1. Central nervous system: Perinatal asphyxia, neonatal encephalopathy, cerebral palsy, intracranial hemorrhage, chromosomal anomalies including down syndrome and inborn errors of metabolism e.g., aminoacidurias, mucopolysaccharidosis, and cerebral lipidosis.
  1. Spinal cord lesions: Anterior horn cell disease – Werdnig Hoffman disease, poliomyelitis.
  1. Peripheral nervous:  Acute polyneuropathy, familial dysautonomia, congenital sensory neuropathy.
  1. Myoneural junction: Neonatal myasthenia gravis, infantile botulism, following antibiotic therapy.
  1. Muscles: Muscular dystrophies, congenital myotonic dystrophies, congenital myopathies (including central core disease and nemaline myopathy), polymyositis, glycogen storage disease (Pompe’s), and arthrogryposis multiplex congenital.
  1. Miscellaneous: Protein-energy malnutrition, rickets, Prader Willi syndrome, malabsorption syndromes, Ehler-Danlos syndrome


Presenting Complaints:
– Decreased Tone
– Difficulty sucking, chewing; Weak cry
– Decreased movement
– Delayed motor milestones
– Complications of muscle weakness:
• Recurrent respiratory infections,
• Respiratory difficulty
Age of Onset:
– SMA Type I : < 6 months;
– SMA Type II: 3mo- 15 mon
– SMA Type III: at or after 12 mon
– Neonatal myasthenia – soon after birth;
–  Juvenile myasthenia – >6 mo
Sudden onset: Intraventricular hemorrhage in Premature infants
• Distribution of weakness:
– Proximal (Unable to stand from sitting) – Myopathies
– Distal (Unable to hold things) – Neuropathy
Associated Atrophy of muscles:
– Myopathies,
– neuropathies
Muscle pain:
– Acute polyneuropathies,
–  myositis,
–  Metabolic disease,
–  Ischemic myopathies
Joint deformities
• Chromosomal disorder
• Congenital Muscular dystrophy,
• Myotonic dystrophy,
• Transitory Neonatal myasthenia
• Congenital dislocation of the hip
CNS causes:
– Seizures
– Abnormal movement
– Mental restriction, Learning disabilities, ataxia
– The poor state of alertness
– Lack of response to visual and auditory stimuli
– Dysmorphic features
– Respiratory difficulty (Involvement of respiratory muscles)
– Apnea
– Aspiration (Gag reflex lost)
H/o Fatigue on continuous sucking – Myasthenia
H/o Constipation – Botulism
H/o easy bruising, poor wound healing – Ehler-Danlos
Dysmorphic Features:
– Down’s Syndrome
– Cerebral dysgenesis,
– Zellweger syndrome,
– Prader-Willi Syndrome
– Fiber type Disproportion myopathies,
– Neonatal myotonic Dystrophies
Birth H/o:
– Antenatal:
• Decreased Fetal movement
• Polyhydramnios
– Perinatal asphyxia: Prolonged/Difficult labor, Delayed cry (Cerebral palsy)
– Breech delivery – Spinal cord injury (lower cervical); Cephalic presentation (upper cervical)
– IUGR, LBW – Decreased muscle mass
Nutritional h/o
Development h/o:
– Delayed milestones
Family h/o: A family history of neuromuscular abnormalities may be informative because many disorders are inherited. Examples of familial neuromuscular diseases include
•  congenital myotonic dystrophy,
• spinal muscular atrophy,
•  metabolic disorders (e.g., mitochondrial disease, acid maltase deficiency, defects of creatine synthesis).


Detection of Hypotonia:

Main Features:
– Bizarre or Unusual postures
– Decreased resistance of joints to passive movement
– Increase in range of movement of joints
– Decreased Spontaneous movements

The appearance of the Floppy Infant:

Supine position:
– The paucity of spontaneous movement
– Fully abducted at hip joint
– Thighs externally rotated (Frog-leg posture)
– Arms extended or flexed at the elbow with hands beside the head
Sitting Posture:
– Head falls forward
– Trunk control poor
– Unable to sit unsupported
Vertical suspension:
– Hold at axilla
– Head falls forward
– Legs dangle or scissoring (Normally flex)
– A tendency to slip through one’s hands
Horizontal suspension:
– Normally, head erect, back straight, limbs flexed
– Hypotonic – head and legs hang limply, Ragdoll
– Unable to lift head and trunk
Palpation of muscles: Flabby
Adductor angle: Angle between thighs when hips maximally abducted with extension at knees
Popliteal angle: Hips flexed onto the abdomen by holding at the knees
Dorsiflexion angle of the foot: By gentle pressure on the sole
Heel to ear maneuver: Both extended legs lifted towards the ears without lifting the pelvis
Scarf sign: Flexed at the elbow and pulled across the chest by holding at the hand and wrist
Deep Tendon Reflexes:
– Central: Normal or Increased
– Ant horn cells: Absent
– Peripheral nerves: Decreased or absent even if residual movement present
– NMJ: Normal
– Muscles: Decreased (Usu. not absent)


Down’s Syndrome
Prader-Willi: Narrow bifrontal diameter of skull, almond-shaped eyes, small hands, and feet
Zellweger: Pear-shaped head, high forehead, wide suture, high arched palate, hypertelorism
Microcephaly (CP), Macrocephaly (Hydrocephalus, Toxoplasmosis, Meningomyelocele)
Facial features :
– alert, bright (SMA) / ptosis (MG)
– Expressionless (Cong. myopathies, Myotonic dystrophy, MG)
– Tongue fasciculations (SMA)
– Fish mouth “triangular” (congenital myopathies, myotonic dystrophy)
–  CP, Intrauterine Infections


– Ptosis, Diplopia – Myasthenia gravis
– Ptosis, Dilated, sluggish pupils – Botulism
– Congenital cataract- Congenital rubella
– Glaucoma – Lowe (oculocerebrorenal syndrome)
– Retinitis pigmentosa- Neonatal adrenoleukodystrophy
– Ptosis, Ophthalmoplegia – Fiber type Disproportion
– Chorioretinitis (TORCH)
– Cardiomyopathy – Myotonic Dystrophy
– CHF, Cardiomegaly – Pompe’s
– Polycystic Kidney Disease (Zellweger)
– Renal tubular acidosis (Lowe)
– Biliary cirrhosis and liver failure- Lowe


•  Serum Creatine Kinase: Prior to EMG or Biopsy
– ↑↑ in rapidly progressive myopathies
– Maybe normal in Fiber type Disproportion myopathies and some metabolic myopathies
– May ↑ in rapidly progressive neuronopathies (SMA)

Electrodiagnostic Test:

– Myopathies – Brief, small amplitude, Polyphasic potentials (BSAPPs)
• Muscular Dystrophies, Myotonic Dystrophies
– Neuropathies- Denervation potentials at rest (Fibrillations, Fasciculations, Sharp waves) and Motor unit potentials large in size, prolonged and polyphasic
• Nerve Conduction Test:
– Demyelinating Conditions – Slower velocity
– Helps localize the site of traumatic nerve injury
– Repetitive nerve stimulation:
• Increase in size of motor unit potentials – Infantile botulism
• Decremental response – Myasthenia Gravis
• Muscle Biopsy:
 Characteristic Findings in Muscle Biopsy:
Groups of small fibers adj to Normal or hypertrophied Type I fibers
Fiber Type Disproportion
Type I Fiber predominant but smaller
Myotubular myopathy
Persistence of Fetal myotubules
Central Core Disease
Cores of closely packed myofibrils with central degeneration of Type I
Nemaline (Rod)
Rod-like particles + Type I predominance
Characteristic Findings in Muscle Biopsy:
Carnitine deficiency
Vacuoles with lipids, Low carnitine levels in muscles
Acid maltase deficiency
Vacuoles with glycogen
Cytochrome c oxidase deficiency
Vacuoles in Type I fibers with abundant glycogen and lipids
Phosphofructokinase deficiency
Subsarcolemmal and intermyofibrillar glycogen
Phosphorylase deficiency
Peripheral vacuoles with glycogen
Characteristic Findings in Muscle Biopsy:
Muscular Dystrophy
Extensive Fibrosis, Proliferation of adipose tissue, regeneration, and degeneration of fibers, thickened muscle spindle capsule
Myotonic Dystrophy
Type II predominance, not completely filled with myofibrils
Infantile Myositis
Diffuse Inflammation and Proliferation of Connective Tissue
Nerve Biopsy: Sural nerve
– Demyelination
– Multifocal endoneurial edema, Mononuclear infiltrates – CIDP
– Metabolic products
Tensilon Test:
– Edrophonium 0.15mg/kg sc in neonates, response in 10 mins
– 0.2mg/kg iv in infants, response in 1 min
Serum Acetylcholine receptor Protein Antibody
• Stool – Clostridium botulinum
• CSF examination:
– Increased protein (Albumino-cytological Dissociation) – GBS, Congenital hypomyelinating neuropathy
– Acid maltase deficiency: Short PR, High QRS in all leads
Chest X-Ray:
– Pneumonia
– CHF: Acid maltase deficiency, Carnitine deficiency
CT Scan of head/MRI:
– Intraventricular/parenchymal hemorrhage
– CNS malformations
– Ischemic changes
EEG: Epileptiform activities
Chromosome analysis: Trisomy 21- Down’s, Chromosome 15 translocation – Prader Willi
X-Ray/MRI of Spine

Other causes:

• Investigations for liver, renal involvement


• A multidisciplinary approach- pediatricians, neurologists, neonatologists, geneticists, occupational therapists, physical therapists, speech therapists, orthopedics, pathologists and specialized nursing care
• Most have no cure and have a progressive course
– Provide Life support: Resuscitation, Feeding support
– Prevent and relieve contractures- Physiotherapy, Casts, Surgical management
– Prevent and treat Infections (Pneumonia)
Specific Treatment of Cause:
– Gabapentin, Riluzole, Caspase inhibitors in SMA
– Prednisolone for CIDP, Inflammatory Myopathies
– High Protein diet in Pompe’s
– L-carnitine replacement in carnitine deficiency
• Genetic Counseling
• Psychological support, Counselling of parents

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