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Central vs Peripheral Hypotonia — RACP Paediatrics MCQ

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ModerateNeurology & DevelopmentCentral vs Peripheral HypotoniaRACP Paediatrics

A 9-month-old baby is referred because he is not sitting unsupported. He has axial hypotonia with head lag on pull-to-sit. He has brisk knee reflexes and extensor plantar responses bilaterally. What pattern of neurological findings is this?

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Correct answer: C — Upper motor neuron pattern (central hypotonia with pyramidal signs)

Central (upper motor neuron) hypotonia presents with axial hypotonia (floppy baby) plus preserved or brisk reflexes and pyramidal signs (extensor plantars). This pattern suggests a brain aetiology (HIE, malformation, genetic). Peripheral hypotonia shows reduced reflexes, weakness, and normal or low tone without pyramidal signs.

Reference: RACP – 2024 – Paediatric Curriculum: The Floppy Infant