Imaging neonatal spontaneous pneumomediastinum usi

Authors: Ah Young Jung Ik Yang Hee Sun Go SuMi Shin HyeKyung Yoon Ji Young Woo HyeSuk Hong Han Myun Kim

Publish Date: 2013/05/15

Volume: 41, Issue: 1, Pages: 45-49

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Abstract

Among neonates with abnormal mediastinal radiolucency suspected on chest radiography those referred for ultrasound examination within 2 days were included Anterior mediastinal ultrasound was performed using a linear transducer 5–12 MHz to determine the presence and location of abnormal air in the mediastinum Clinical data for the neonates were also reviewedOn ultrasound pneumomediastinum appeared as thick linear/curvilinear echogenic lines some with posterior shadowing located between the anterior chest wall and thymus in lateral margins of the thymus between the thymus and the great vessels and in the middle of the thymic parenchymaNeonatal pneumomediastinum occurs in approximately 25 per 1000 live births 1 The underlying mechanism is alveolar rupture with leakage of air into the lung interstitium and dissection of that gas into the hilum and subsequently the mediastinum 2 Most spontaneous pneumomediastinum in neonates is associated with birth injury prematurity pneumonia meconium aspiration syndrome or assisted ventilation 3 The infant is often asymptomatic or presents with mild respiratory distress and the condition usually resolves spontaneously 4 The diagnosis of pneumomediastinum is usually based on chest radiography and physical examination However chest radiography may not be diagnostic especially when there is only a small amount of gas collection in the thoracic cavity In such cases ultrasound may be helpful in demonstrating the presence of a small amount of abnormal air in the mediastinum because the relatively unossified thoracic cavity of neonates along with the presence of a large thymus allows a good acoustic window 5 6 Despite many advantages of ultrasound in neonates there is little information regarding the use of ultrasound for evaluation of abnormal air in the mediastinum The purpose of this study is to investigate the feasibility of using ultrasound to detect neonatal spontaneous pneumomediastinum and to describe the sonographic featuresThe study included consecutive neonates hospitalized in the NICU between April 2010 and November 2010 Neonates with abnormal mediastinal radiolucency on chest radiography were identified Among these neonates those referred for ultrasound study of the brain or abdomen within 2 days of radiolucency detected on chest radiography were enrolled Unstable neonates and neonates with extensive pneumomediastinum limiting evaluation of the air distribution on ultrasound were excluded Approval was given by our Institutional Review BoardMediastinal sonograms were obtained after performing routine scanning of the referred brain or abdomen area Mediastinal sonography was performed with the neonates in the supine position using a 5 to 12MHz linear array transducer iU22 Philips Medical Systems Bothell WA USA The transducer was placed directly over the anterior chest wall to visualize the thymus and great vessels During the sonographic examination several transverse and longitudinal scans were obtained to assess the presence and distribution of the abnormal air The hospital records of the neonates were reviewed for age at ultrasound examination sex gestation at delivery birth weight mean Apgar score mode of delivery presence of underlying conditions such as meconium aspiration respiratory symptoms and clinical course

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