Preterm Infant With Hypotonia

History and Physical

A male infant was born at 33 ⁺¹ weeks of gestation by emergency cesarean section in the setting of breech positioning, hypotonia, and prolonged bradycardia of 60 beats/minute. Birth weight was 1860 g. The baby was born in breech presentation, and Apgar scores at 1 and 5 minutes were 2 and 4, respectively. In the delivery room, the infant experienced significant respiratory distress prompting intubation. Neurologic examination showed hypotonia and few spontaneous movements including eye opening. EEG demonstrated continuous low-voltage patterns.

Diagnostic Workup

Head US on day 2 of life showed prominent extra-axial spaces. Brain MRI at 18 days showed confluent restricted diffusion throughout the cerebral white matter with medullar venous injury ( Fig. 11.1 ). Follow-up MRI at 45 days showed development of large areas of cystic encephalomalacia with global volume loss ( Fig. 11.2 ).

An M R I with six axial brain sections labeled A to F shows multiple arrows that point to linear and dotted features in the deep and peripheral white matter. — Fig. 11.1

An M R I with four axial brain sections labeled A to D shows multiple arrows that point to cystic spaces in the white matter near the ventricles and cortex. — Fig. 11.2

Clinical Differential Diagnoses

Differential diagnoses for neonatal hypotonia include hypoxic-ischemic encephalopathy, intracranial hemorrhage, cerebral malformations, chromosomal abnormalities, intracranial infection, peroxisomal disorders, inborn errors of metabolism, and maternal drug use. The diagnostic algorithm should include history and physical examination, neuroimaging, neurogenetic and biochemical testing, and muscle and nerve investigations.

Imaging Differential Diagnoses

Periventricular leukomalacia (PVL) consists of two distinct pathologic components: focal necrosis and diffuse cellular injury involving preoligodendrocytes in cerebral white matter with astrogliosis and microgliosis.

Global hypoxia-ischemia is more common in term infants.

Metabolic brain disorders such as molybdenum cofactor deficiency ( Fig. 11.3 ) and bilirubin encephalopathy ( Fig. 11.4 ).