SIDS or not SIDS? Classification problems of sudden infant death syndrome

Death-scene investigations contribute to legal protection in unexpected child deaths in Norway

AIM

This study reviewed cases of sudden unexpected child deaths in Norway to determine the significance of death-scene investigations (DSIs) in establishing cause and manner of death, and thereby it is relevance to legal protection.

METHODS

Data from forensic autopsy reports and DSIs were collected and analysed for cases of unexpected deaths in children below 4 years of age in Norway during 2010-2016.

RESULTS

Out of 141 cases, the death scene was investigated as a voluntary procedure in 75 cases and by the police in 41 cases. The cause of death remained unexplained in 81/141 (57%) of the cases, of which 46/141 (33%) met the criteria for sudden infant death syndrome (SIDS) or sudden unexplained death in early childhood (SUDC). The manner of death was determined in 102/141 (72%). Voluntary DSI increased the ability to rule out accidental suffocation, facilitated evaluations of environmental risk factors and enabled detection of possible neglect.

CONCLUSION

Death-scene investigations illuminate uncertainty about the cause of death, especially in grey-area cases where accidental suffocation, neglect or abuse is suspected. Knowledge about the course of events and the cause of death enhances both the child's and the caregiver's legal protection. Death-scene investigations should therefore be mandatory.

A single-centre review of suspected sudden infant death cases

This study aimed to establish the number of deaths in infants under 1 year of age that were being reported for medico-legal examination at a single large academic centre in Hungary, as well as the method of these investigations with special emphasis on histopathology, ancillary techniques and the adherence of our current practice to international recommendations. A single-centre, retrospective audit was conducted on all suspected sudden infant death cases. After the review there were eight infectious background sudden infant death syndrome (SIDS) cases, infectious respiratory tract disease in 14 cases, cardiac septal tumour in one case, and hepatic, possibly metabolic, disorder in one case. Our study has highlighted that even in a single institution there is a huge heterogeneity of approaches which needs standardisation. A reclassification of infant cases according to the San Diego definition resulted in a decreased number of SIDS cases in our material. The San Diego definition and related international recommendations were found to be practical and the classification provides a guide to the standardisation of current practice.

Reclassification of SIDS cases--a need for adjustment of the San Diego classification?

A study was undertaken reclassifying cases of sudden infant death syndrome (SIDS) taken from two geographically separate locations utilizing the San Diego definition with subclassifications. One hundred twenty-eight infant cases were examined from files at Forensic Science South Australia in Adelaide, SA, Australia over a 7.5-year period from July 1999 to January 2007. Thirty-one cases (24%) had initially been diagnosed as SIDS and 30 (23%) as undetermined while 67 (52%) had an explainable cause of death. After reclassification, the number of SIDS cases had increased to 49 of the 128 cases, now representing 38% of the cases; category IB SIDS constituted 10 (20%) and II SIDS 39 (80%) of the SIDS cases. No cases were classified as IA SIDS. Two hundred eighteen infant cases were identified from the files of the Department of Forensic Medicine, Aarhus University, Denmark over a 16-year period from 1992 to 2007. Eighty-two (38%) were originally diagnosed as SIDS, 128 (59%) with identifiable causes of death, and 8 (4%) as unexplained. After review, 77 (35%) cases were reclassified as SIDS, a decrease of 6%. Twenty (26%) infants were classified as category IB SIDS and 57 (74%) as II SIDS. None of the cases met the criteria for IA SIDS. Problems arose in assessing cases with failure to thrive, fever, and possible asphyxia. Modifications to the San Diego subclassifications might improve the consistency of categorizing these cases.

Evaluation of diagnostic tools applied in the examination of sudden unexpected deaths in infancy and early childhood

During the period between 1984 and 1999, 309 cases of sudden unexpected death in infancy and early childhood (0-3 years) were investigated at the Institute of Forensic Medicine in Oslo. In 73 cases, an explainable cause of death was found. In this non-sudden infant death syndrome (SIDS) group, 42 cases were due to disease, 14 to accidents, 7 to neglect/abuse and 10 cases were due to homicide. In 43 cases, there were pathological findings at the autopsy or suspect features in the history and/or circumstances, which were, however, insufficient to explain death ("borderline" SIDS). In the remaining 193 cases, nothing of significance was detected ("pure" SIDS). The purpose of the present study was to evaluate the importance of the different diagnostic tools used in diagnosing non-SIDS and borderline SIDS cases. The definition of SIDS requires a negative history as well as a negative autopsy result. Thus, the following variables were analysed: circumstances, medical history and autopsy, which included a gross pathological investigation, histology, neuropathology, microbiology, radiology and toxicology. In diagnosing deaths due to disease, histology, neuropathology and microbiology were the most important diagnostic tools. In contrast, information about the circumstances of death and the gross pathological findings at autopsy most often revealed the cause of death in accidents and cases of neglect/abuse and homicide. Following the drop in SIDS rate in Norway after 1989, the share of pure SIDS in proportion to the total population of sudden unexpected deaths in infancy and early childhood has decreased. The increasing proportion of non-SIDS and borderline SIDS cases presents a challenge to improve the quality of the investigation in cases of sudden death in infancy and early childhood.

Inflammatory responses in sudden infant death syndrome -- past and present views

Sudden infant death syndrome (SIDS) is sudden unexpected death in infancy for which there is no explanation based on commonly accepted diagnostic criteria; however, half of the victims have had slight signs of infection prior to death. Such slight infection with fever is an important risk factor in combination with a prone sleeping position, especially in infants between 2 and 4 months of age. The purpose of this review is to summarise findings that support the theory that a significant part of cot deaths may be due to an overreaction to otherwise harmless infections. Such factors are mucosal immune stimulation, cytokines in the cerebrospinal fluid and hypoxanthine levels in vitreous humour. The review aims at explaining why we believe that a slight infection combined with a prone position, a warm environment and a vulnerable age period may trigger a vicious circle leading to death.

Use of new Nordic criteria for classification of SIDS to re-evaluate diagnoses of sudden unexpected infant death in the Nordic countries

To investigate whether changes in diagnostic practice might be the cause of the SIDS epidemic in the Nordic countries in the 1970s and 1980s a cooperative study was initiated in 1990. Common morphologic diagnostic criteria for SIDS were established in 1992 and 127 randomly selected sudden unexpected infant deaths from all Nordic countries from 1970 to 1995 and 205 cases from the Institute of Forensic Medicine, Oslo, Norway (RMI) from 1984 to 1995 were re-evaluated blindly using the new criteria. Neither the increase nor the decline in the SIDS rate since 1989 seemed to be due to changed diagnostic practices. SIDS seemed to have been under-diagnosed before the new criteria came into operation in 1992. There were fewer discrepancies between the original and revised diagnoses in the RMI cases than in the rest of the Norwegian cases, both before and after 1992.