Abstract
The hypotonic newborn represents a real challenge for the clinician in search of the etiology. Perinatal antecedents and a proper physical examination are fundamental to exclude frequent pathologies.
The first step thing is to rule out systemic disorders such as hypothyroidism, hypoglycemia, hypocalcemia and sepsis, and that the newborn is not under the effect of sedative or relaxant drugs.
It is important to classify the hypotony according to its origin in central (upper motor neuron) or peripheral (lower motor neuron). Central origin is more frequent and among these, hypoxic-ischemic encephalopathy the most common. Genetic test became the progress for these entities, and now there are available tests for disorders such as spinal muscular atrophy, myotonic dystrophy, Prader-Willi syndrome and hereditary neuropathies. Particularly important is the group of “benign” hypotonies, where all tests are negative and the prognosis is good. The hypotonic newborn requires a multidisciplinary management.
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