Forensic Science, Medicine and Pathology

, Volume 14, Issue 1, pp 42–56 | Cite as

Neuronal apoptosis in the brainstem medulla of sudden unexpected death in infancy (SUDI), and the importance of standardized SUDI classification

  • Natalie Ambrose
  • Karen A. Waters
  • Michael L. Rodriguez
  • Kendall Bailey
  • Rita MachaalaniEmail author
Original Article


The purpose of this study was to examine the neuronal expression of apoptotic markers in the rostral medulla of a newly characterized dataset of sudden unexpected death in infancy (SUDI), and to determine the impact of diagnostic groupings on these findings and whether they pertain to the intrinsic apoptotic pathway. Immunohistochemical staining was quantified to determine the percentage of neurons positive for active caspase-9 (specific to the intrinsic apoptotic pathway), active caspase-3 (common to the intrinsic and extrinsic apoptotic pathways) and Terminal deoxynucleotidyl transferase mediated dUTP nick-end labelling (TUNEL) (labels DNA fragmentation) in nine nuclei of the rostral medulla. Expression was compared between groups of SUDI infants where the cause of death was initially classified by a forensic pathologist or subsequently after reclassification by an expert panel using the San Diego Criteria. 68 SUDI infants were studied and originally classified as explained SUDI (n = 12), Sudden Infant Death Syndrome (SIDS) (n = 27) and undetermined (n = 29). Reclassification resulted in a decrease in the number of explained SUDI cases to 7 and a decrease in the number of undetermined cases to 4, with a corresponding increase in the number of SIDS cases to 57 (8 SIDS I; 49 SIDS II). The expression of apoptotic markers was similar in explained SUDI and SIDS I infants. However, TUNEL expression was greater in the cuneate (p < 0.001), vestibular (p = 0.01) and hypoglossal (p < 0.001) nuclei and active caspase-3 expression was lower in the arcuate nucleus (p = 0.037) in SIDS II compared to explained Sudden Unexpected Death in Infancy (eSUDI) infants. Compared to SIDS I infants, SIDS II infants had greater TUNEL expression in the dorsal motor nucleus of the vagus (p < 0.01) and greater active caspase-9 expression in the medial and spinal vestibular nuclei (p = <0.01). Changes in apoptotic expression predominated in SIDS II infants. We postulate that these are due to a combination of contributing risk factors including the presence of an upper respiratory tract infection and bed-sharing/co-sleeping. The absence of changes in active caspase-9 expression compared to eSUDI indicates that the intrinsic apoptotic pathway is not upregulated in SIDS.


Active caspase-3 Brainstem Caspase-9 TUNEL SUDI classification San Diego criteria SIDS 



The tissue used in this study was provided by the NSW Forensic and Analytical Science Service. The authors acknowledge the facilities, and scientific and technical assistance of the Australian Microscopy and Microanalysis Research Faculty at the Australian Centre of Microscopy and Micro Analysis, University of Sydney. Research was funded by the SIDS Stampede, Australia, and the Miranda Belshaw Foundation.


This study was funded by philanthropy (SIDS Stampede, Australia and the Miranda Belshaw Foundation, Australia).

Compliance with ethical standards

Informed consent

This type of study no formal consent was required.

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

Ethical approval was from the NSW Health RPAH Zone (X13–0038 & HREC/13/RPAH/54) and University of Sydney Ethic committees.

Supplementary material

12024_2018_9954_MOESM1_ESM.pdf (178 kb)
ESM 1 (PDF 178 kb)


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Medicine and The Bosch InstituteThe University of SydneySydneyAustralia
  2. 2.Discipline of PathologyThe University of SydneySydneyAustralia
  3. 3.The Children’s HospitalSydneyAustralia
  4. 4.NSW Department of Forensic MedicineGlebeAustralia

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