Autopsies of sudden infant death syndrome--classification and epidemiology

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.

Postmortem computed tomography for detecting causes of sudden death in infants and children: retrospective review of cases

PURPOSE

The aim of this study was to investigate the usefulness of postmortem computed tomography (PMCT) in detecting causes of sudden death in infants and children.

MATERIALS AND METHODS

Our subjects were 15 nontraumatically deceased patients (nine boys and six girls, ranging in age from 20 days after birth to 12 years old, mean age 1.6 years), who had been in a state of cardiopulmonary arrest on arrival at our hospital. PMCT was performed within 2 h after certification of death: head (15 cases), chest (11 cases), and abdomen (12 cases). Blood was collected from 11 of the patients at the time of cardiopulmonary resuscitation. An autopsy was conducted on two.

RESULTS

PMCT did not show any traumatic changes indicating child abuse. It was difficult to presume the cause of death with PMCT alone, but the cause of death in 14 of 15 cases could be presumed by combining information from their medical history, clinical course before death, PMCT findings, laboratory data, and bacterial culture. The remaining subject was classified as cause unknown.

CONCLUSION

The causes of sudden death in infants and children were detected at a high rate when we comprehensively investigated the PMCT and other examination findings.

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.

[Trends in infant mortality in France: frequency and causes from 1950 to 1997]

OBJECTIVES

To present an analysis of the infant mortality trends and causes of death in France from the beginning of the 1950s, neonatal (0-27 days) and post-neonatal mortality (27-364 days) being considered separately.

MATERIAL AND METHODS

We used the data from the national registries of births computed by INSEE (National Institute of Statistics and Economic Surveys) and of causes of deaths computed by Inserm (National Institute of Health and Medical Research). We analysed the evolution of the infant death rates from 1950 to 1997, the overall mortality for males and the percentages of causes of death at three different periods.

RESULTS

Mortality has changed according to neonatal or post-neonatal ages. A constant improvement was recorded for neonatal mortality up to 1995 (2.9 per 1,000), while there was a stagnation for post-neonatal mortality between 1979 and 1993, followed by a sharp decrease (2.0 per 1,000 in 1995). During the neonatal age the main causes of death are conditions generated in the neonatal period and congenital abnormalities, both decreasing regularly; during the post-neonatal age the main cause is sudden infant death syndrome, which fell dramatically during the last four years.

CONCLUSION

Several factors related to medical care, nursing and type of registration are contributing simultaneously to the important variations in mortality found in our results.

Sleeping environments as risk factors of sudden infant death syndrome in Japan

For the purpose of assessing the risk factors of the sleeping environment in SIDS, we performed a population-based, case-control study. Index cases comprised 56 SIDS cases which were diagnosed on the basis of autopsies during a period of 11 years at the Department of Legal Medicine, Faculty of Medicine, University of the Ryukyus. Control cases comprised infants who were examined at regional health centers for Infant Health Screening. The incidence of SIDS obtained was 0.25 per 1000 live births, which was comparable to that obtained in other districts having the established medical examiner's system. The proportion of prone sleeping was 81.0% and 38.3% in the SIDS and control groups, respectively, and an odds ratio was calculated as 10.4 (99% confidence interval, 3.9 to 37.6). This indicates that prone sleeping is a risk factor of SIDS, in Japan, as reported in various countries. Various kinds of bedclothes were used in this country, and our survey of bedclothes in the control revealed their improper use for infants to sleep, particularly with the prone position. In addition, the co-sleeping habit, which was not uncommon in Japan, seems to contribute to certain deaths of infants whose causes of death were controversial. In the investigation of SIDS, therefore, the sleeping environments, such as bedclothes and the co-sleeping habit, as well as the sleeping position should be taken into consideration as risk factors.

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.

Sudden infant death syndrome, virus infections and cytokines

Many epidemiological risk factors identified for sudden infant death syndrome (SIDS) suggest a viral aetiology, e.g. exposure to cigarette smoke and winter peak, mild respiratory symptoms. Virus infections and bacterial toxins induce cytokine activity and it has been suggested that uncontrolled inflammatory mediators could be involved in some cases of SIDS. The aim of this review was to assess the evidence for virus infection in SIDS and to examine those findings in relation to individual variations in cytokine responses and various pathophysiological mechanisms proposed for SIDS such as sleep derangement, hypoxia, cardiac arrhythmia, vascular hypotonicity and hypoglycaemia.

Sudden infant death syndrome: a search for allergen hypersensitivity

BACKGROUND

Sudden infant death syndrome (SIDS) remains a diagnosis by exclusion which leaves few if any pathologic clues to its etiology. Previous evaluations for anaphylaxis in SIDS have been few and limited.

OBJECTIVE

To analyze forensic blood specimens for evidence of anaphylaxis in 51 (43 boys and 8 girls) children dying of SIDS and 13 (9 boys and 4 girls) age-matched controls who died from defined, nonanaphylactic causes.

METHODS

Specimens collected over a 5-year period were assayed for (1) total IgE (IU/mL) by immunoenzymatic assay; (2) latex, cat, dust mite (Dermatophagoides farinae and Dermatophagoides pteronyssinus), milk, soy, wheat, peanuts, egg, and tomato specific-IgE by RAST; and (3) serum tryptase levels (U/L) by radioimmunoassay.

RESULTS

The 51 SIDS cases (median age 3 months; range 1 to 9 months) and 13 control cases (median age 4 months; range 1 to 11 months) demonstrated similar total IgE of 9.8 +/- 1.1 IU/mL (mean +/- SEM) and 10.9 +/- 2.8 IU/mL (P = .59). The frequency of detectable (> 0.5 U/L) serum tryptase levels among SIDS cases (10/51) was similar to controls (3/13, P = .72). The frequency of positive RAST tests was 39% (20/51) in SIDS and 38% (5/13) in control subjects (P = .99). Differences in frequencies of positive RAST tests in SIDS and control cases were not statistically significant for any allergen tested. The most frequently detected allergen-specific IgE, to milk, was similar in SIDS (22%) and controls (31%, P = .48).

CONCLUSIONS

Elevated tryptase levels and allergen-specific IgE (milk, soy, wheat, peanuts, egg, tomato, dust mites, cat, and latex) were demonstrated in some infant SIDS deaths but were no more common than in controls. We conclude that anaphylaxis is probably an uncommon etiology for SIDS.

Temporal disparity between reduction of cot death and reduction of prone sleeping prevalence

According to several reports sudden infant death rates have decreased significantly after public campaigns aimed at reducing the incidence of sleeping in a prone position. The Styrian population (1.2 million inhabitants), who have been studied from 1984, also showed a significant drop in the incidence of cot death during 1989 (from 2/1000 to 1/1000%). The year before, a campaign for the prevention of cot death had been launched. This included the recommendation to prevent infants from lying in a prone position during sleep. Part of the prevention programme consisted of a detailed questionnaire filled in and returned by the parents. These data, on 29970 infants from 1989 to 1994, provided information on the frequency of prone sleeping in 37% of our total population and as a consequence on parental response to the campaign. Calculating the data per year led to the surprising result that the reduction by half (from 50% to 25%) in the prevalence of sleeping in a prone position did not occur in 1989, when the drop in the incidence of cot death occurred, but 3 years later, in 1992. The following years saw a further decrease of prone position to 7% but no appreciable change in the incidence of cot death. However, during those 11 years of study about 80% of the victims were consistently found dead lying in a prone position. Our results show a temporal disparity between the reduction of sudden infant death and the decrease of prone sleeping in a population. Although we do not deny sleeping in a prone position as a risk factor for cot death, there cannot be a simple relationship between sleeping habits in the population and incidence of cot death.