Spontaneous neonatal pneumomediastinum

doi:10.4236/ojped.2011.13010

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Open Journal of Pediatrics, 2011, 1, 37-38 OJPed

doi:10.4236/ojped.2011.13010 Published Online September 2011 (http://www.SciRP.org/journal/ojped/).

Published Online September 2011 in SciR es. http://www.scirp.org/journal/OJPed

Spontaneous neonatal pneumomediastinum

Kiran Kumar Balegar V.1, Nadia Badawi1, Arieta Fa’asalele2, Kathryn Carmo1,2

1Department of Neonatology, Royal Alexandra Hospital for Children, Westmead, Australia;

2Newborn & Paediatric Emergency Transport Service, Westmead, Australia.

Email: [email protected];

Received 18 June 2011; revised 26 July 2011; accepted 26 August 2011.

ABSTRACT

Radiolucency in the superior mediastinum may be

caused by a congenital cystic mass or pneumomedi-

astinum. Most cases of pneumomediastinum occur in

preterm newborns with surfactant deficiency receiv-

ing treatment with positive pressure ventilation. Sp-

ontaneous pneumomediastinum in term neonates is

also rarely reported. We report the outcome for a

term neonate with respiratory distress who was tran-

sferred for surgical evaluation of a cystic superior

mediastinal mass.

Keywords: Spontaneous Pneumomediastinum; Superior

Mediastinal Mass; Neonate

1. INTRODUCTION

A male infant of 38 weeks gestation and birth weight of

3520g was referred to The Children’s Hospital at West-

mead, Australia for the surgical management of a radio-

lucent superior mediastinal mass. The infant was born by

elective caesarean section to a primiparous woman after

an uncomplicated pregnancy, in a regional hospital. Ap-

gar scores were 7 and 9 at one and five minutes, resp ec-

tively. Shortly after birth he developed mild respiratory

distress requiring treatment with head box oxygen. The

respiratory distress worsened over the next 24 hours and

oxygen requirement increased to 50% although blood

gas analysis and haemodynamics remained stable. Chest

x ray at this stage revealed a radiolucent superior medi-

astinal shadow. He was commenced on CPAP and the

state Newborn Emergency Transport Service (NETS)

team was contacted regarding advice and transfer. Re-

view of an x-ray film through telemedicine and multid-

isciplinary discussion with the receiving neonatologist,

transport team and cardiothoracic surgeon indicated the

possibility of pneumomediastinum. It was agreed to dis-

continue the CPAP and transfer the baby by road in crib

oxygen, rather than by air, despite the longer travel time.

The follow-up chest x-ray at the tertiary centre revealed

a classical Spinnaker sail sign of a pneumomediastinum

(Figure 1) with an otherwise normal appearance of the

lung fields. Conservative management in head box oxy-

gen resulted in complete resolution of the pneumomedi-

astinum over the subsequent 72 hours (Figure 2).

Figure 1. Chest x-ray on admission showing cys-

tic appearance and Spinnaker sail sign of pneu-

momediastinum.

Figure 2. Chest x-ray after 72 hours showing

complete resolution of pneumomediastinum.

K. K. Balegar V. et al. / Open Journal of Pediatrics, 2011, 1, 37-38

2. DISCUSSION

Although most reported cases of neonatal pneumomedi-

astinum ensue exposure to positive pressure in the set-

ting of premature or diseased lungs [1-3], spontaneous

pneumomediastinum that occurs in the absence of clear-

ly defined precipitating factors, has rarely been reported

[4,5]. Pathogenesis of pneumomediastinum was first

demonstrated experimentally by Macklin in 1939 [6].

Exposure to an increased pressure gradient between the

alveoli and the pu lmonary interstitium results in alveolar

rupture into the perivascular space, at the junctional area

between compliant bronchial airway and poorly compli-

ant alveoli. Air dissects along the perivascular sheaths

towards the hilum and leaks into loose connective tissue

spaces of the mediastinum. The usual triggering agent is

positive pressure ventilation in combination with an un-

derlying abnormality such as surfactant deficiency or

meconium aspiration syndrome that renders the alveoli

more fragile and prone to rupture [7]. In spontaneous

pneumomediastinum the pressure gradient is thought to

be generated by excessive negative intrapleural pressure

during vigorous respiratory efforts in term infants, cou-

pled with an uneven inflation o f alveoli at birth [8]. This

is the most plausible explanation in our infant.

Although chest roentgenography can be diagnostic in

most cases of pneumomediastinum, the appearance may

be confused with other surgical cystic mediastinal le-

sions such as congenital cystic adenomatoid malforma-

tion or congenital lobar emphysema, as illustrated in our

case. This is because of the unique anatomical feature of

the neonatal thymus characterized by a thick fascial

capsule which envelopes the thymus and merges with

the fibrous pericardium [8]. Air tends to loculate around

the thymus and sometimes can even dissect within the

interlobular and connective tissue septa of the thymic

capsule, giving rise to a cystic appearance. It is postu-

lated that this cystic appearance is uncommon in older

children and adults because the thymus and its fascia

undergo atrophy and are unable to contain a sudden air

leak [5,8].

Suspicion of pneumomediastinum prevented us from

using aggravating factors such as CPAP or positive

pressure ventilation. Between the 2 available options

namely, transporting the baby in pressurised air transport

vehicle at a lower altitude versus road transport - we

chose the latter so as to avoid the possible disastrous

effects from expansion of gases in the closed spaces at

lower ambient air pressure (as dictated by Boyle’s law).

A careful evaluation of the x-ray film in our case re-

vealed the crescentic configuration of the elevated

thymic lobes resembling a windblown Spinnaker sail.

Serial x-ray films showing evolution of the pneumome-

diastinum with this classic Spinnaker sail sign followed

by complete resolution avoided CT scan, which other-

wise is the investigation of choice to confirm the nature

of a mediastinal mass.

Most cases of spontaneous pneumomediastinum re-

solve spontaneously. Timely recognition and avoidance

of aggravating factors constitute th e crux of management

and prevent deterioration and haemodynamic instability

[7].

3. KEY POINTS

Neonatal pneumomediastinum can be confused with

surgical cystic radiolucent mass owing to the unique

anatomical feature of the neonatal thymus characterized

by a thick enveloping fascial capsule that contains air.

Awareness of spontaneous pneumomediastinum in

newborn babies with respiratory distress helps to direct

the nature of respiratory support and the mode of trans-

port. With timely recognition and avoidance of aggra-

vating factors, most cases resolve spontaneously.

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