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Hypotonia (Low Muscle Tone): definition and ICD-11 features
Hypotonia is reduced resting muscle tone — a clinical sign, not a diagnosis. ICD-11 codes it under signs (MB47.4). In early childhood the priority is localising central versus peripheral causes, since aetiology drives both pathway and prognosis.
In this answer 4 sections
The floppy infant on your examination couch is a clinical sign, not a diagnosis — the work is in finding the why.
In short
Hypotonia is reduced resting muscle tone — diminished resistance to passive movement — presenting as the "floppy infant", head lag, slipping-through-on-vertical-suspension and an inverted-U on ventral suspension. It is a sign, not a disease, and ICD-11 codes it under symptoms/signs rather than as a discrete entity (see MB47.4 Hypotonia within the muscle-tone abnormalities cluster). The clinical imperative is to localise: central (brain/spinal) versus peripheral (anterior horn cell, nerve, NMJ, muscle), as this determines aetiology and pathway.
The science, briefly
In early childhood, central hypotonia predominates (~60–80%) and typically pairs low tone with preserved or brisk reflexes, cognitive involvement and later spasticity — think hypoxic-ischaemic injury, chromosomal/genetic syndromes (Down syndrome, Prader-Willi), or metabolic disease. Peripheral hypotonia features weakness, hyporeflexia and is anatomically localised (SMA, congenital myopathies, myotonic dystrophy, transient neonatal myasthenia). Red flags warranting prompt referral: feeding/respiratory difficulty, fasciculations, regression, dysmorphism, or absent reflexes. Functionally, frame against ICF activity-participation domains — feeding, postural control, gross-motor milestones — rather than tone alone.
The Pinnacle way
Developmental measurement supports care planning; diagnosis requires an appropriately qualified healthcare professional., under qualified clinician care — never from an online form. We pair aetiological clarity with function-led occupational and physiotherapy and a measurable AbilityScore® baseline. Read more on hypotonia.
Trusted sources
WHO ICD-11 (symptoms and signs involving the musculoskeletal system); WHO ICF framework; AAP developmental surveillance guidance.
Next step — Refer a floppy infant for combined aetiological and functional assessment at a Pinnacle centre.
CONNECT THE ANSWER TO YOUR CHILD’S DAY
Something to notice. Something to discuss.
What to notice
Feeding or respiratory difficulty, head lag persisting beyond expected age, absent reflexes, fasciculations, dysmorphic features, or any developmental regression.
In everyday life
When assessing a floppy infant, always document reflexes alongside tone — preserved reflexes point central, depressed reflexes point peripheral.
Bring your observations and questions to your child’s professional. Choose activities that suit your child’s comfort, abilities and agreed plan.
Bring your questions to a first visitQuestions families ask
Is hypotonia a diagnosis on its own?
No — hypotonia is a clinical sign of reduced muscle tone. ICD-11 codes it under symptoms and signs (MB47.4), and the diagnostic task is identifying the underlying central or peripheral cause.
How do you distinguish central from peripheral hypotonia?
Central hypotonia typically shows preserved or brisk reflexes with cognitive involvement; peripheral hypotonia features weakness, hyporeflexia and a localisable lesion in the anterior horn cell, nerve, neuromuscular junction or muscle.
When should a floppy infant be referred urgently?
Promptly with feeding or respiratory compromise, absent reflexes, fasciculations, dysmorphism, regression, or persistent parental concern — these may signal serious neuromuscular or metabolic disease.
FOLLOW THE SOURCE
References behind this answer.
- Organisation website · further readingWHO ICD-11 — symptoms and signs
- Organisation website · further readingWHO ICF functioning framework
- Organisation website · further readingAAP developmental surveillance guidance
References are supplied with this answer. An organisation homepage offers further reading; it does not establish an independent review of this page.
Content attribution: SETU Consortium · Pinnacle Blooms Network.
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