Neuromuscular disorders in the newborn.

The main manifestations of neuromuscular disease in the newborn period are hypotonia and weakness. Infants with severe hypotonia but only marginal weakness usually do not have a disorder of the lower motor unit. These infants may have genetic conditions, metabolic disturbances, congenital heart disease, hypothyroidism, sepsis, or other systemic disorders. Early on, neonates with central nervous system pathology may present with profound hypotonia, decreased reflexes, and moderate to severe but transient weakness. However, they also tend to have seizures, obtundation, cranial nerve signs, or history of perinatal asphyxia.