Massive Amniotic Fluid Aspiration in a Case of Sudden Neonatal Death With Severe Hypoplasia of the Retrotrapezoid/Parafacial Respiratory Group

Abstract

We report a case of a baby, who, after pregnancy complicated by maternal Addison's disease and Hashimoto's thyroiditis and natural delivery, unexpectedly presented a cardiorespiratory collapse and died 1 hour after birth without responding to prolonged neonatal resuscitation maneuvers. The cause of death was reliably established by carrying out a forensic postmortem examination. More specifically, the histological examination of the lungs showed the presence of abundant endoalveolar and endobronchial cornea scales caused by absorption of amniotic fluid. The neuropathological examination of the brainstem highlighted severe hypodevelopment of the retrotrapezoid/parafacial respiratory group, which is a complex of neurons located in the caudal pons that is involved in respiratory rhythm coordination, especially expiration, in conditions of enhanced respiratory drive, as well as in chemoreception. This neuropathological finding shed new light on the mechanisms underlying the massive amniotic fluid aspiration which led to this early death.

Keywords: amniotic fluid inhalation; brainstem; hypoplasia; newborn; retrotrapezoid/parafacial respiratory group; sudden neonatal death.

Figure 1

Histological section of lung showing the presence of abundant endoalveolar and endobronchial corneal scales into the alveoli. Staining: hematoxylin/eosin; Scale bar: 50 μm.

Figure 2

(Right) Schematic representation of the brainstem sampling: I = ponto-mesencephalic specimen, including the upper third of the pons and the adjacent portion of mesencephalon; II = caudal pontine specimen; III = medulla oblongata specimen, including the obex; IV = sample extending from the caudal pars of the medulla oblongata to the rostral spinal cord. (Left) schematic representative histological sections obtained from the four specimens, indicating the main nuclei and structures to be examined.

Figure 3

An image series related to the retrotrapezoid/parafacial respiratory group (RTN/pFRG). At the top, on the right: ventral brainstem schematic image with the indication (red arrow) of the optimal sampling for the examination of the human RTN/pFRG in the caudal pons; on the left: whole histological section at this level with the indication of the RTN/pFRG localization. (A) Histological section of medulla oblongata showing in the circled area the normal cytoarchitecture of the RTN/pFRG, adjacent to the facial nerve (fn) in an age-matched control case. (B) Severe hypoplasia of the RTN/pFRG observed in this case. (C) Cluster of PHOX2B immunoreactive neurons identifier of the RTN in the control case. (D) Lack of PHOX2B immunoreactivity in the RTN region. (A,B) Staining: Klüver-Barrera; (C,D) Staining: PHOX2B immunohistochemistry. Scale bar (A–D): 100 μm.

Figure 4

An image series related to the arcuate nucleus (AN). At the top, on the right: ventral brainstem schematic image with the indication (red arrow) of the optimal sampling for the examination of the human AN in the medulla oblongata (at the obex level); on the left: whole histological section at this level with the indication of the AN localization. (A) Histological section showing (red arrows) the normal structure of the AN at the ventral medullary surface in an age-matched control case. (B) Severe hypoplasia of the AN observed in this case. (A,B) staining: Klüver–Barrera; Scale bar (A,B): 100 μm.