Approach to Floppy infant

  Floppy infant syndrome:

a term used to describe reduced muscle tone and muscle weakness in infants.Hypotonia :

decrease resistance to passive range of motion  Weakness :

Reduce power of active motion

Floppy infant:

Is not uncommon neurologic condition in infancy.

A variety of neuromuscular disorders and central nervous system (CNS) disorders cause floppy infant syndrome (FIS).

CNS disorders are the much more common causes of the syndrome than neuromuscular disorders

It is often helpful to divide causes into those that are

‘central’ involving the CNS (so-called ‘floppy strong’)

and ‘peripheral’ involving lower motor neurons, neuromuscular junction (NMJ), or primary muscle disease (‘floppy weak’).

HISTORY

History

Sx : weakness :proximal,distal, fatigability myalgia

Clinical course of the disease (static ,progressive)

Developmental hx : delay , regression Associated sx

prenatal, Perinatal , postnatal hx Neonatal hx : Respiratory effort, Ability to feed,

Level of alertness, Level of spontaneous activity, Character of cry

 Nutritional hx: sucking and swallowing difficulties that ‘fatigue’ or ‘get worse’ with repetition.

Family hx : premature death , …

Clinical Features

Range of clinical features

Common to ‘central’ and ‘peripheral’ diseases: generalized hypotonia; ‘frog-leg’ posture; respiratory failure; obstetric problems (e.g. polyhydramnios due to impaired swallowing, breech presentation); hypoxic–ischaemic encephalopathy.

Central conditions: encephalopathy; dysmorphism; reasonable muscle strength; increase or normal tendon reflexes.

Peripheral causes: normal conscious level; muscle signs (weakness, myotonia, fasciculations, or fatiguing); decrease or normal tendon reflexes; little facial expression; micrognathia; high arched palate; ptosis; undescended testes; limbcontracture/deformities; hip dislocation

Causes of‘Floppy strong’ or ‘central’ involving CNS

Prematurity HIE Hypoglycaemia Sepsis Electrolyte disturbance Drug-related IEM Hypothyroidism

Chromosomal disorders (e.g. trisomy 21)

CNS malformations Benign congenital

hypotonia Underlying syndrome

(e.g. Prader–Willi syndrome)

Cervical spinal cord trauma (birth injury)

Causes of ‘Floppy weak’

‘Spinal muscular atrophy (SMA), particularly type 1 (previously known as Werdnig–Hoffman disease)

Myasthenia gravis (transient or congenital) Congenital myotonic dystrophy (autosomal dominant

inheritancefrom mother) Congenital muscular dystrophies Congenital myopathies Metabolic myopathies Peripheral neuropathies Spinal cord injury

Anatomical-clinical correlation illustrating differential diagnosis

Muscle – Duchenne muscular dystrophy: 

X linked recessive, presents with waddling gait and difficulty climbing stairs

Neuromuscular transmission – juvenile myasthenia : >10 years old*ophthalmoplegia and ptosis *loss of facial expression and difficulty chewing

Peripheral nerve

–  Hereditary motor sensory neuropathies 

(HMSN): symmetrical wasting of the distal muscles

–  Acute post-infectious polyneuropathy 

(Guillain–Barré syndrome): ascending 

symmetrical weakness; may be bulbar palsy and respiratory depression

Anterior horn cell 

– spinal muscular atrophy: 

progressive weakness and wasting of skeletal muscles; tongue fasciculation may aid diagnosis

Management

Exclude severe systemic illness: e.g. sepsis that requires prompt

treatment. Treat any respiratory failure with O2 or ventilatory

support as required. Examine both parents for possible disease, e.g.

maternal myasthenia gravis or myotonic dystrophy (possibly undiagnosed!).

Elicit family history (e.g. maternal myotonic dystrophy); antenatal history (e.g. polyhydramnios).

‘Central’ cause: consider—

blood glucose; U&E; Ca++; Mg ++Septic screen; ESR/CRP; TFT; karyotype; cranial ultrasound; CT/MRI; EEG;

IEM (inborn errors of metabolism) screen; maternal drug screen; genetics opinion if dysmorphic.

‘Peripheral’ cause: consider—serum creatinine phosphokinase; specifi cytogenetics (e.g. myotonic dystrophy);

electromyogram (EMG) ,nerve conduction studies; muscle or sural nerve biopsy; muscle ultrasound;

edrophonium 20micrograms/kg test dose l followed 30s later (if no adverse reaction) with 80micrograms/kg IV

(causes dramatic improvement in some forms of myasthenia gravis ;)

) (echocardiogram storage diseases

Spinal cord damage (rare): consider in the infant who has a flaccid paralysis from birth. Associated with rotational forceps delivery.

Immobilize neck. Seek specialist advice. MRI.

Prognosis

Causation-dependent and very variable.

Some causes are fatal, e.g. type 1 SMA.

References

Illustrated Textbook of Pediatrics, Fourth Edition, Tom Lissauer

Oxford handbook of Pediatrics ,2nd edition, Robert Tasker

الله جزاكمخيرا