Neonatal hypotonia: is it a diagnostic challenge?

INTRODUCTION: Hypotonia is a frequent sign of disease in newborns. However, it's a nonspecific clinical finding: may be the presentation form of a systemic or neurological disease.

AIMS: To study the main causes of neonatal hypotonia as well as to evaluate the diagnostic accuracy of the anamnesis and physical examination of the hypotonic newborn.

PATIENTS AND METHODS: A 22-year retrospective study of hypotonic neonates admitted to the Neonatal Intensive Care Unit was conducted. It was performed an initial blind classification of hypotonia's type (central-CH, peripheral-PH or undetermined hypotonia) based on the clinical history and the recorded data of physical examination.

RESULTS: 91 infants were included. 42 (46.2%) had prenatal history abnormalities: polyhydramnios (28.6%), intrauterine growth restriction (21.4%) and pelvic presentation (19.0%). 53 (58.2%) required resuscitation at birth. The main associated symptoms were respiratory distress (65.9%), feeding difficulties (36.5%) and decreased spontaneous movements (22.4%). The final diagnosis was reached in 64 newborns (70.3%): 81.3% with CH, 18.7% with PH. The positive predictive value of the initial classification was 97.9% in CH and 66.7% in PH group. The mortality rate was 8.8% and it was higher in PH group (58.3% vs 1.3%).

CONCLUSIONS: Neonatal hypotonia can be associated to an extensive list of disorders. A detailed clinical history associated to a careful neurological evaluation present a high diagnostic predictive value that should guide the etiological investigation.