Neuromuscular diseases frequently present in newborns or infants with hypotonia and weakness. However, these signs also occur in many common disorders such as sepsis, organ failure, and metabolic dysfunction. If these latter conditions can be excluded, hypotonia probably is caused by a primary neuromuscular disorder.
Assessment of the infant with hypotonia and weakness is reviewed here. The causes of hypotonia and weakness caused by peripheral nerve and muscle diseases (table 1) and the evaluation of specific neuromuscular disorders are discussed elsewhere. (See "Overview of peripheral nerve and muscle disorders causing hypotonia in the newborn".)
The obstetric and perinatal history may provide information that supports the diagnosis of a neuromuscular disorder. Affected infants frequently have a history of polyhydramnios (caused by decreased fetal swallowing), fetal akinesia (paucity of movement), and malpresentation (often in the breech position).
Delivery may be complicated by birth trauma or perinatal depression. Although these complications can occur in normal infants, infants with congenital neuromuscular disorders may be less able to tolerate the stress associated with labor and delivery and, thus, be more susceptible to birth depression.
A family history of neuromuscular abnormalities may be informative because many disorders are inherited. Examples of familial neuromuscular diseases are congenital myotonic dystrophy, spinal muscular atrophy, metabolic disorders (eg, mitochondrial disease, acid maltase deficiency, defects of creatine synthesis), and familial dysautonomia.