THE FLOPPY INFANT

•	Presentation.
•	Causes.
•	History.
•	Clinical examination.
•	Investigations.

Definition

1.	A floppy infant is a baby who is almost toneless, like a rag-doll.

2.	Presentation

a.	Bizarre and unusual postures of infant: e.g. ‘frog-leg’ posture.

b.	Decreased resistance to passive movements – hypotonia.

c.	Increased range of movements of joints – hyperextension.

d.	Usually relatively immobile – paucity of movements.

e.	Presents with delayed motor milestones.

3.	Age groups

a.	Neonate: poor sucking and swallowing.

b.	Infant: 

i.	delayed motor development and milestones

ii.	not gaining head control. 

c.	Later: abnormal gait and difficulty in climbing stairs.

Causes

1.	Clinical situations associated with hypotonia

Prematurity	•	Normal, physiological.	
Acute illness of childhood	•	Gastroenteritis.
•	Dehydration.
•	Septicaemia.	
Cerebral abnormality	•		
Diffuse CNS dysfunction	•	Down’s.
•	Prader Willi.
•	Cerebral palsy.	
Neuromuscular disorders	•	SMA.
•	Congenital myotonias.	
Connective tissue disorders	•	Marfan’s.
•	Ehler Danlos.	

2.	Site of lesion causing floppiness

Site	Causes	
General	•	Prematurity.
•	Septicemia.	
Brain	•	Cerebral palsy.
•	Down’s syndrome.
•	Prader-Willi syndrome.	
Spinal cord	•	Spinal cord transection during breech delivery.
•	Cord maldevelopment: myelodysplasia.
•	Infantile SMA.
•	Poliomyelitis.	
Motor neuron	•	Guillian-Barre.
•	Acute inflammatory polyneuropathy.	
Neuromuscular junction	•	Myasthenia Gravis.
•	Infantile botulism.
•	Toxic neuromuscular blockage.	
Muscle	•	Congenital myopathy.
•	Duchenne muscular dystrophy.
•	Hypokalaemic / hyperkalaemic periodic paralysis.	

3.	Distinguishing central and peripheral causes

Central	Peripheral	
Non-paralytic conditions with hypotonia and no significant weakness.	Paralytic conditions with incidental hypotonia. 	
Involves:
•	CNS: cerebral cortex.
•	Systemic organs.
•	Connective tissues.	Involves:
•	Peripheral nervous system.
•	Anterior horn cells.
•	Nerve fibers.
•	Neuromuscular junction.
•	Muscles.	
Mental retardation	Usually intellectually normal.	
Deep tendon reflexes normal or increased.	Deep tendon reflexes decreased or absent.	
May have persistence of primitive reflexes.	No abnormal persistence of primitive reflexes.	
Mild weakness.	Severe weakness.	
Can move against gravity.	Unable to move against gravity.	

4.	Cerebral causes

a.	Atonic CP is the most common neurologic cause of floppy infant syndrome.

b.	Types:

i.	spastic.

ii.	choreoathetosis.

iii.	ataxia.

c.	All the above 3 have in common a phase of hypotonicity seen within.

d.	Features:

i.	occurs between 2 – 4 years of age.

ii.	always with brisk reflexes.

iii.	primitive reflexes still persist.

e.	Mental retardation:

i.	Down’s syndrome: spot diagnosis.

ii.	Prader-Willi syndrome: obese hypogonadism.

5.	Spinal Muscular Atrophy

a.	SMA is the most common neuromuscular cause of FIS.

b.	Autosomal recessive inheritance.

c.	Onset < 6 months of age.

d.	Mean life expectancy: 6 months from onset.

e.	Progressive deterioration, death usually by respiratory failure. 

f.	Antenatal features:

i.	+ / - reduced fetal movements.

ii.	+ / - orthopaedic deformities at birth. 

g.	Clinical features:

i.	bright look in contrast to paucity of movement.

ii.	‘frog-leg’ posture.

iii.	severe hypotonia and weakness: no anti-gravity movements.

iv.	absent reflexes.

v.	tongue fasciculations.

vi.	extraocular movements not affected.

vii.	paradoxical respiration: chest moves in, abdomen moves out.

viii.	proximal to distal muscle weakness. 

h.	SMA type 2:

i.	normal development for the first 6 months of life.

ii.	can sit unaided but never stands.

iii.	arrest of motor milestones by 18 months of age.

iv.	weakness symmetrical, proximal worse than distal, lower limbs worse than upper limbs.

v.	intercostal muscles weak, diaphragm spared.

vi.	no bulbar symptoms, but has fasciculations and atrophy of tongue.

vii.	tremor of the upper extremities.

viii.	survival into adolescence or adulthood.

I.	SMA type 3:

i.	normal milestones in the first year of life.

ii.	subsequently able to walk, then show weakness.

iii.	wadling gait, difficultly in climbing steps.

iv.	tremors of hands.

v.	maintains ambulation for many years.

vi.	may show little decline. 

j.	Investigations.

i.	neuropathic EMG: giant motor units with fasciculations and fibrillations.

ii.	normal / minimally elevated CPK.

iii.	muscle biopsy: neuropathic pattern with group atrophy and characteristic perinatal denervation pattern. 

6.	Guillain-Barre syndrome

a.	A post-infectious demyelinating neuropathy occurring 1 – 3 weeks after trivial viral infection.

b.	Clinical features:

i.	symmetrical weakness, progressive over 1 – 2 weeks.

ii.	respiratory muscle and facial weakness – can lead to respiratory failure.

iii.	muscle pain and paraesthesia.

iv.	urinary retention or incontinence.

v.	disturbance of autonomic function.

c.	Investigations:

i.	nerve conduction: delay in motor and sensory conduction.

ii.	CSF: increase in protein without increase in cells. 

d.	Treatment:

i.	IVIG: reduce duration and severity.

ii.	supportive therapy, with spontaneous recovery usual in 2 – 3 weeks.

7.	Neuromuscular junction pathologies

Disease	Consistent features	Variable features	
Transient neonatal myasthenia	•	Hypotonia.
•	Affected mother.
•	Course < 12 weeks.
•	+ ve Tensilon test.	•	Degree of weakness.
•	Antibodies to AchR.	
Congenital myasthenia	•	Fixed ophthalmoparesis.
•	Non-affected mother.
•	No antibodies to AchR.
•	Fatigable muscles.	•	Response to Tensilon.	
Botulism	•	Pupillary non-reactivity.
•	Bulbar weakness.
•	Post-tetanic facilitation.
•	Presence of toxin.
•	Areflexia.	•	Fatigable weakness.
•	Response to Tenslon.	
Toxic	•	Antibiotics: streptomycin, neomycin.
•	Anticholinesterase: insecticides, organophosphates.		

8.	Congenital myopathies

a.	Inheritance may be:

i.	autosomal dominant.

ii.	autosomal recessive.

iii.	sex-linked recessive.

b.	All present with hypotonia and delayed motor development.

c.	Some present with marked skeletal deformities: high incidence of congenital dislocation of the hips. 

d.	High tendency of developing malignant hyperthermia under GA.

9.	Myotonic dystrophy

a.	Usually mother and not father is involved.

b.	Autosomal dominant inheritance.

c.	Clinical features:

i.	ptosis, expressionless facies, facial diplegia, inverted ‘V’ appearance of upper lip.

ii.	swan-like neck.

iii.	dull and monotonous voice.

iv.	extreme floppiness.

v.	respiratory and feeding difficulties.

vi.	myotonia: inability to relax after contraction; not present until age 3 – 5 years.

vii.	joint deformities, esp. club feet. 

d.	Confirmation of diagnosis by DNA studies.

10.	Duchenne Muscular Dystrophy

a.	Most common hereditary neuromuscular disease with an incidence of 1:3500.

b.	Insidious onset: usually after 1 year of age.

c.	Inheritance:

i.	sex-linked recessive.

ii.	usually boys affected.

iii.	female carriers usually asymptomatic.

d.	Presentation:

i.	abnormal gait: waddling.

ii.	frequent falls.

iii.	difficulty in climbing steps.

iv.	floppy.

e.	Clinical features:

Examination	Signs	
Inspection	•	Pseudohypertrophy of calves.
•	Lordosis and scoliosis.
•	Contractures of hip flexors, tendon-Achilles.
•	Equinovarus deformity of feet due to muscle imbalance.	
Gait	•	Wide base, waddling gait.
•	Tendency to walk on toes.	
CNS	•	Proximal weakness and wasting.
•	Reflexes: absent in UL and knee jerk; ankle jerk preserved till late.	
Gower’s sign	•	Proximal weakness of pelvic girdle.
•	Put child on floor – to get up, child goes on all 4 limbs and climb on LL with hands for support.	
Arm-slip sign	•	Weakness of shoulder girdle.
•	Test for winging of scapula.	

f.	Prognosis:

i.	cannot walk by 9 years.

ii.	death before age 20 from respiratory infection.

iii.	mild intellectual impairment of IQ 84 – 90. 

g.	Diagnosis

Test	Results	
Serum muscle enzymes	•	Grossly elevated CPK with > 1000 IU/L.
•	Level decreased with progression of disease.	
Muscle biopsy	•	Muscle fiber degeneration and regression.	
EMG	•	Characteristic dystrophic picture.	
Immuno-histochemistry	•	Absence of dystrophin. 	

Clinical Examination

1.	Aims

a.	Confirm presence of floppiness.

b.	Differentiate central and peripheral causes.

c.	Assess exact etiology.

2.	General observation

a.	Look at parents’ face:

i.	myotonic dystrophy.

ii.	myasthenia gravis.

b.	Dysmorphic features:

i.	Down.

ii.	Prader-Willi.

iii.	MPS.

c.	Parameters: head size.

d.	Facial features:

i.	bright and alert faces: SMA.

ii.	mask-like facies: Duchenne’s.

iii.	myotonic facies with facial diplegia: myotonic dystrophy.

iv.	ptosis and opthalmoplegia: myasthenia gravis.

e.	Tongue fasciculations: SMA.

f.	NG tube / gastrostomy: feeding difficulties in CP, SMA.

g.	Oxygen catheter: respiratory problems in SMA, CP. 

h.	Chest:

i.	tachypnoea: aspiration with SMA, Pompe, congenital MD.

ii.	paradoxical breathing: SMA.

iii.	bell-shaped chest: SMA.

3.	Examination of limbs

a.	Compare:

i.	upper and lower limbs: spina bifida affects lower limbs.

ii.	left and right sides: spastic hemiplegic CP.

iii.	proximal and distal groups of muscle: SMA may be associated with some degree of sparing of the hands and feet, e.g. finger and toe movement only.

b.	Inspect:

i.	posture: ‘frog-leg’ confirming floppiness.

ii.	fasciculations in SMA. 

iii.	movements: paucity of movement; movement against gravity implies power of at least 3/5 and possible central cause.

iv.	muscle bulk: any wasting; which group of muscles are moving.

v.	muscle biopsy sites. 

c.	Tone:

i.	pull to sit: detect degree of head control / lag.

ii.	sitting: degree of head / trunk control; ability to sit unsupported.

iii.	attempted weight bearing: to detect lower limb hypotonia, weakness and scissoring.

iv.	ventral suspension: assess degree of hypotonia (infant curved up like a ‘C’), back for lumbar myelomeningocele and extensor posture in CP. 

v.	lay infant prone: describe degree of head control and ability to lift head / trunk.

d.	Joint mobility:

i.	confirm hypotonia.

ii.	contractures: osteogenesis imperfecta, arthrogryposis.

iii.	joint hyperextensibility: connective tissue disorders.

iv.	hip dislocations: congenital myopathies.

e.	Reflexes:

i.	deep tendon: brisk – central causes; decreased / absent – SMA, peripheral causes.

ii.	primitive: persistent in central causes. 

f.	Power:

i.	> 3/5: central causes.

ii.	< 3/5: peripheral causes.

4.	Systemic review

a.	Respiratory distress / abnormal thoracic cage in SMA.

b.	Cardiomegaly and hepatomegaly in Pompe’ disease.

Investigations

1.	Central floppiness: majority are due to mental retardation and cerebral palsy.

2.	For problems related to birth, a careful history is often revealing, investigate for:

a.	Chromosomal disorders.

b.	Metabolic disorders.

c.	Endocrine disorders.

3.	Neuromuscular problems

a.	Muscle enzyme estimation:

i.	creatine phosphokinase: most consistent and reliable; increased up to 50% in Duchenne and Becker syndrome.

ii.	Aldolase.

iii.	SLDH, SGOT.

b.	Results:

i.	congenital myopathies: normal or slightly raised.

ii.	congenital muscular dystrophy: usually moderately raised.

iii.	SMA: usually normal.

4.	Nerve conduction studies

a.	Decreased in neuropathy.

b.	Axonal: normal or slightly decreased.

c.	Demyelinating: decreased in e.g. Guillian-Barre.

5.	Electromyogram

a.	Distinguish myopathic from neuropathic process.

b.	Difficult to interpret in a small infant due to lack of voluntary effort.

c.	Two patterns seen:

Myopathic	Neuropathic	
•	Low amplitude.
•	Polyphasic potentials of short duration.	•	Spontaneous fibrillation at rest.
•	Giant action potentials.
•	High amplitude.
•	Long action potential.	

6.	Muscle biopsy

a.	To diagnose:

i.	structural myopathies by histology.

ii.	specific enzyme deficiency by histochemistry.

b.	Two patterns seen:

i.	myopathic pattern: structural abnormalities of muscle fibres.

ii.	neuropathic pattern: group atrophy of muscle fibers with variation in muscle fiber size.