Causes of Floppy Infant
- 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.
- Spinal cord lesions: Anterior horn cell disease – Werdnig Hoffman disease, poliomyelitis.
- Peripheral nervous: Acute polyneuropathy, familial dysautonomia, congenital sensory neuropathy.
- Myoneural junction: Neonatal myasthenia gravis, infantile botulism, following antibiotic therapy.
- 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.
- Miscellaneous: Protein-energy malnutrition, rickets, Prader Willi syndrome, malabsorption syndromes, Ehler-Danlos syndrome
History:
• 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
• Severity:
– 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).
Examination:
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
• Prone:
– 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)
Dysmorphism:
• 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)
Deafness:
– CP, Intrauterine Infections
Association:
• Ocular:
– 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)
• Cardiac:
– Cardiomyopathy – Myotonic Dystrophy
– CHF, Cardiomegaly – Pompe’s
• Renal:
– Polycystic Kidney Disease (Zellweger)
– Renal tubular acidosis (Lowe)
• Hepatic:
– Biliary cirrhosis and liver failure- Lowe
Investigations
• 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:
• EMG:
– 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:
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Disorders
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Characteristic Findings in Muscle Biopsy:
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SMA
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Groups of small fibers adj to Normal or hypertrophied Type I fibers
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Fiber Type Disproportion
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Type I Fiber predominant but smaller
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Myotubular myopathy
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Persistence of Fetal myotubules
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Central Core Disease
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Cores of closely packed myofibrils with central degeneration of Type I
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Nemaline (Rod)
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Rod-like particles + Type I predominance
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Disorders
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Characteristic Findings in Muscle Biopsy:
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Carnitine deficiency
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Vacuoles with lipids, Low carnitine levels in muscles
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Acid maltase deficiency
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Vacuoles with glycogen
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Cytochrome c oxidase deficiency
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Vacuoles in Type I fibers with abundant glycogen and lipids
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Phosphofructokinase deficiency
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Subsarcolemmal and intermyofibrillar glycogen
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Phosphorylase deficiency
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Peripheral vacuoles with glycogen
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Disorders
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Characteristic Findings in Muscle Biopsy:
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Muscular Dystrophy
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Extensive Fibrosis, Proliferation of adipose tissue, regeneration, and degeneration of fibers, thickened muscle spindle capsule
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Myotonic Dystrophy
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Type II predominance, not completely filled with myofibrils
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Infantile Myositis
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Diffuse Inflammation and Proliferation of Connective Tissue
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• 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
• ECG:
– 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:
• TFT
• TORCH
• Investigations for liver, renal involvement
Management:
• 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
• Aim:
– 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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