Neonatal hypotonia

Neonatal hypotonia represents a commonly encountered issue in the NICU and newborn nursery. Low tone is not a diagnosis in itself but, rather, a symptom. This review focuses on the special case of diffuse hypotonia presenting in the neonatal period. Etiologies are broad and include systemic illness, dysfunction of the central nervous system, or dysfunction of the peripheral nervous system and motor unit (ranging from disorders of the anterior horn cell to primary muscle disease). In this time of rapidly expanding therapeutic options for many diagnoses causing hypotonia, expeditious evaluation is crucial. Careful physical examination, thorough history, and appropriately selected ancillary testing guides the diagnostic process.