Hypotonia in infancy (Floppy infant)

Hypotonia in infancy raises suspicion of an underlying neuromuscular disease, but acutely unwell children are also floppy and lethargic.

Causes of hypotonia are grouped as:

CENTRAL causes:

 – Hypothyroid

 – Down’s Syndrome

 – Prader-Willi

 – Inborn Errors of Metabolism

 – Cerebral dysgenesis

 

Other:

 – Prematurity, Sepsis

 – Hypoxic Ischaemic Encephalopathy

 – Maternal opiates

PERIPHERAL causes: 

Anterior Horn cell disease

  – SMA

  – Pompe

Peripheral Nerve

  –  Inflammatory – GBS

  –  Demyelinating /  Axonal

  – Metabolic- Leigh

Neuromuscular Junction

  – Myasthenias

  – Infantile botulism

Muscle disorders

  – Congenital Myopathy 

  – Muscular dystrophy

  – Myotonic dystrophy

History key enquiries:

– Feeding issues?

– Breathing issues?

– Seizures? Dysmorphism?

– Developmental progress

 

Mother:

any illness, fever, substance abuse

Pregnancy

polyhydramnios,

reduced foetal movt, or malpresentation

Delivery

complicated/ prolonged, trauma, APGAR;

Family history

delayed milestones, weakness, myotonia

 

Examination GENERAL:

Is neonate preterm/ unwell / septic?

HIE features? Pale? Bruised?

Is term neonate requiring NG feeds?

Any obvious congenital anomaly-

external? Midline defects? hypogonadism or hypospadias?

RS: Resp- rate? Diaphragmatic movt? Good cry?

CVS: Cardiomegaly? Murmur? Femorals?

Abdo: Organomegaly? Underdeveloped scrotum?

 

Examination NEUROLOGY:

Alertness- encephalopathic?

Eye movements- able to fix & follow?

Facial muscle movements

Suck & swallow, tonge movements / fasciculations

Spontaneous fisting or an abnormal primitive reflex?

Posture, including tone

Spontaneous movt- more proximal / distal?

Any anti-gravity movements? Weakness?

Deep tendon reflexes

Plantar reflexes (esp if over 1y age)

Investigations:

Common early tests:

Bloods: Electrolytes, Mg, Ca, Glucose, CK

Metabolic: pH, Lactate, Pyruvate, NH3, S.AA, TFT’s;

Urine Organic acids & Amino acids

MRI Brain imaging

Karyotype (Microarray) & Gene testing- SMA, PWS

 

Further specialist tests:

CSF neurotransmitters,

VLCFA, other genetic tests,

auto-antibodies, etc

Electromyography /Nerve Conduction

Muscle biopsy

MR spectroscopy

 

Management principles:

– Reach definitive diagnosis to plan management & give prognosis

– Management of associated congenital anomaly/ cardiac dysfunction

 

Respiratory support – ? non-invasive ventilation and/or tracheostomy prevention (influenza and pneumococcal vaccination) and prompt treatment of respiratory infections

Orthopaedic intervention for joint contractures / postural deformities

Support Feeding – nasogastric feeding, caloric supplementation, gastrostomy?

Physiotherapy – aimed at prevention of contractures & deformities

Occupational therapy – improvement of function; consider appliances

Early intervention with developmental care and stimulation of learning