SPECIAL ARTICLE |






* Department of Pathology, Childrens Hospital San Diego, University of California, San Diego, School of Medicine, San Diego, California
Department of Pathology and Human Anatomy, Loma Linda University, Loma Linda, California
Forensic Science Centre and Departments of Paediatrics and Pathology, University of Adelaide, Adelaide, Australia
|| Rettsmedisinsk Institutt and University of Oslo, Oslo, Norway
¶ Institut fur Rechtsmedizin and University of Essen, Essen, Germany
# Office of the Chief Medical Examiner and University of Louisville School of Medicine, Louisville, Kentucky
** Department of Pediatric Laboratory Medicine, The Hospital for Sick Children and the University of Toronto, Toronto, Ontario, Canada

Emory University School of Medicine and the Fulton County Medical Examiners Center, Atlanta, Georgia

Division of Pediatric Pulmonology, Childrens Hospital Los Angeles, Los Angeles, California
|||| Department of Paediatrics, University of Auckland, Auckland, New Zealand
| ABSTRACT |
|---|
|
|
|---|
Key Words: SIDS sudden infant death
Abbreviations: SIDS, sudden infant death syndrome
Sudden infant death syndrome (SIDS) is a term that has been used to describe unexpected deaths of infants or young children when subsequent investigations fail to demonstrate a definite cause of death.1,2 The concept, which was first proposed in 1969, has been controversial, and its use has been characterized by great variability in the consistency with which the requirements of standard definitions have been fulfilled.35 Specifically, the term has been overused and applied to cases in which there have been obvious natural or unnatural causes of death; also, the term has been underused in favor of imprecise terms such as undetermined or unascertained. A number of other definitions that have included quite different criteria have been proposed.68 The most widely used definitions have made SIDS a diagnosis of exclusion.
In 1969, at the Second International Conference on Causes of Sudden Death in Infants, it was proposed that SIDS was "the sudden death of any infant or young child which is unexpected by history, and in which a thorough postmortem examination fails to demonstrate an adequate cause of death."1 In 1989, the National Institute of Child Health and Human Development convened an expert panel to reexamine the issue of definition. The panel proposed that SIDS was "the sudden death of an infant under one year of age, which remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history."2(p681) This definition limited the age to <1 year and specified that a thorough examination should include examination of the death scene and review of the clinical history.
In 1992, at the SIDS International Meeting in Sydney, Australia, Bruce Beckwith proposed stratification of the definition to enable separation of cases into typical and atypical groups.9 The proposal was not accepted at the time, although others subsequently supported subclassification.10 In 2003, Beckwith again called for a reexamination of the definition of SIDS, with the possibility of including positive diagnostic criteria and stratification to delineate particular subsets.11 As a result of this proposal, a meeting was held in San Diego, California, in January 2004; it was sponsored by the CJ Foundation for SIDS and involved an invited panel of experts, including pediatric pathologists, forensic pathologists, and pediatricians, all of whom had extensive experience with sudden infant death. Delegates came from Europe, North America, and Australasia.
| DISCUSSION POINTS |
|---|
|
|
|---|
A group discussion followed, during which the advantages of formulating and promulgating a redefinition of SIDS were actively debated. It was agreed that creating and supporting a more inclusive SIDS definition would facilitate uniformity in diagnosis, with a resultant increase in information on current cases. It would also enable accumulated data to be better used and would provide opportunities to propose and evaluate new theories, particularly regarding possible SIDS subsets. Existing SIDS definitions were considered inadequate, often being applied too generally or too restrictively, and were exclusionary, failing to incorporate known features of the syndrome (such as sleep and age range). The conclusions of the group were based on assessments of current trends and data and were intended to be fully reevaluated in the future, when they will likely need to be modified to accommodate new developments.
The redefinition was also considered a useful step to enable more precise monitoring of changing epidemiologic patterns in sudden infant deaths and to allow more valid international comparisons. By more clearly defining subsets of sudden infant deaths, monitoring of the effects of public health recommendations and alterations in infant care practices can be facilitated. Finally, more precise definitions of subsets of sudden infant deaths, with specification of requirements for diagnosis, should help standardize investigative protocol development, by improving examinations of the circumstances of death and autopsy investigations and bringing investigations more in line with recommended guidelines.1214 Providing more information and more rigorous subclassification of cases should also facilitate integrated multiagency approaches to such cases.15
| RESULTS |
|---|
|
|
|---|
General Definition of SIDS
SIDS is defined as the sudden unexpected death of an infant <1 year of age, with onset of the fatal episode apparently occurring during sleep, that remains unexplained after a thorough investigation, including performance of a complete autopsy and review of the circumstances of death and the clinical history.
Category IA SIDS: Classic Features of SIDS Present and Completely Documented
Category IA includes infant deaths that meet the requirements of the general definition and also all of the following requirements.
Clinical
37 weeks).
Circumstances of Death
Autopsy
Category IB SIDS: Classic Features of SIDS Present but Incompletely Documented
Category IB includes infant deaths that meet the requirements of the general definition and also meet all of the criteria for category IA except that investigation of the various scenes where incidents leading to death might have occurred was not performed and/or
1 of the following analyses was not performed: toxicologic, microbiologic, radiologic, vitreous chemistry, or metabolic screening studies.
Category II SIDS
Category II includes infant deaths that meet category I criteria except for
1 of the following.
Clinical
Circumstances of Death
Autopsy
Unclassified Sudden Infant Death
The unclassified category includes deaths that do not meet the criteria for category I or II SIDS but for which alternative diagnoses of natural or unnatural conditions are equivocal, including cases for which autopsies were not performed.
Postresuscitation Cases
Infants found in extremis who are resuscitated and later die ("temporarily interrupted SIDS") may be included in the aforementioned categories, depending on the fulfillment of relevant criteria.
| DISCUSSION |
|---|
|
|
|---|
After implementing a broad overall definition, participants decided to subcategorize SIDS cases on the basis of specific epidemiologic features and the amount of information available. This was prompted partly by the knowledge that the number of classic SIDS cases, typical of those occurring in the 1970s and 1980s (before the Back to Sleep and Reduce the Risks campaigns), had decreased and it was likely that the remaining cases represented a relatively more heterogeneous group, with varied underlying mechanisms of death.
Stratification of cases of sudden infant death into subcategories was therefore undertaken to:
Dividing cases of sudden infant death that fit the general definition of SIDS into subgroups should not have an effect on epidemiologic studies of the syndrome as a whole, because most cases would still be classified as SIDS. However, researchers looking for classic SIDS cases to study could take them from category IA. The group considered it important that researchers specify which subgroups were used for studies, because that would enable immediate assessment of the rigor with which cases had been investigated and determination of how closely the study group represented classic SIDS cases. It was also recommended that future research should be undertaken to examine similarities and differences among the subgroups, which might clarify specific causes.
The age range of 3 weeks to 9 months was chosen on the basis of an analysis of data from the Avon and Confidential Enquiry Into Stillbirths and Death in Infancy studies in the United Kingdom, New Zealand Health Information Services data, the Chicago and San Diego SIDS studies in the United States, studies at the Rettsmedisinsk Institutt in Oslo, Norway, and the Westphalian and German Sudden Infant Death studies in Germany, by Edwin Mitchell. Pooling of data from those studies showed that the 5th to 95th percentile limits for SIDS deaths were
3 weeks to 9 months.
Prone position was considered an established risk factor for SIDS deaths but not a cause of suffocation unless specific circumstances (such as a face-down position on an incompletely filled waterbed or in a thin plastic bag) could be demonstrated. For this reason, infants found prone with no evidence of suffocation could be included in any of the categories, depending on other features. Prone sleeping involves an array of potential problems, including diaphragmatic splinting/fatigue, rebreathing of carbon dioxide, reflex lowering of vasomotor tone with tachycardia, blunting of arousal responses (including decreased cardiac responses to auditory stimulation), alteration of sleep patterns, upper airway obstruction resulting from soft bedding, and overheating, and is most likely a problem only among infants with underlying susceptibilities.17 Similarly, although there is evidence of increased risk of infant death in shared sleeping situations,18 shared sleeping does not automatically exclude SIDS as a possibility, if it can be shown that the infant was not at risk of accidental asphyxia. It should be recognized that the position in which the infant is found sometimes reflects agonal movement and is not necessarily the position of the infant at the onset of the fatal event.
It was acknowledged that a number of different and variably defined terms were being used to classify unexpected infant deaths. Sudden unexpected death in infancy is a general term that covers SIDS and other types of unexpected infant deaths. When an infant dies suddenly and unexpectedly and intentional or unintentional fatal injury can be excluded, death may be attributable to a specific disease entity, such as myocarditis, or to SIDS.19 Deaths that cannot be precisely subcategorized or classified have been deemed undetermined, undeterminable, unascertained, or unascertainable, but this has created concerns about the specificity of these terms. The merits of replacing the term SIDS with sudden unexplained infant death were briefly discussed during the meeting, but it was the consensus of the group that SIDS still served a useful purpose. The term unclassified sudden infant death was proposed to account for cases in which the criteria for category I or II SIDS were not met or an autopsy was not performed. These cases may represent SIDS deaths, but there is insufficient information available to make that judgment or there are certain atypical features, such as inflicted but nonlethal injury, that are insufficient by themselves to establish a cause of death but are thought to preclude use of the term SIDS. Atypical features may also include underlying organic diseases, such as an anomalous coronary artery without evidence of myocardial ischemia, which may also preclude a confident statement about a possible cause of death.
The investigation of infant deaths should be conducted according to established protocols14,20 and should include careful evaluation of the death scene, external examination of the body with photographic documentation, radiologic examination, internal examination with photographic documentation, and histologic, microbiologic, toxicologic, biochemical, metabolic screening, and genetic studies if indicated. Guidelines for and confirmation of the usefulness of such stepwise examinations are available in the literature.2123
Finally, it should be reiterated that these proposals represent nothing more than attempts to improve definitions and to facilitate more accurate investigation, diagnosis, and categorization of cases of unexpected infant death. Considerable public, professional, and media attention has been paid recently to certain high-profile court cases in which the standards of investigation and pathologic analyses were far from acceptable. This does not mean that the underlying concepts are flawed; rather, it means that diagnostic terms and protocols should be more rigorously defined and standard investigative approaches should be maintained. The proposed framework is a work in progress, which will need to be continually reformulated and refined as more knowledge becomes available and our understanding of these complex and challenging cases becomes clearer. (At a pathology workshop in Canberra, Australia, in March 2004, forensic and pediatric pathologists representing forensic institutions and hospitals from all Australian states and territories unanimously endorsed the new general San Diego definition and recommended its national implementation.)
| FOOTNOTES |
|---|
Address correspondence to Henry F. Krous, MD, Childrens Hospital and Health Center, 3020 Childrens Way, M5007, San Diego, CA 92123. E-mail: hkrous{at}chsd.org
Report of an expert panel convened by the CJ Foundation for SIDS, San Diego, California, January 89, 2004 (moderator: Henry F. Krous).
| REFERENCES |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
A Cote, A Bairam, M Deschenes, and G Hatzakis Sudden infant deaths in sitting devices Arch. Dis. Child., May 1, 2008; 93(5): 384 - 389. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. A. King-Hele, K. M. Abel, R. T. Webb, P. B. Mortensen, L. Appleby, and A. R. Pickles Risk of Sudden Infant Death Syndrome With Parental Mental Illness Arch Gen Psychiatry, November 1, 2007; 64(11): 1323 - 1330. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. M Eisenstein, Z. Haklai, S. Schwartz, A. Klar, N. Stein, and E. Kerem Investigation of unexplained infant deaths in Jerusalem, Israel 1996-2003 Arch. Dis. Child., August 1, 2007; 92(8): 697 - 699. [Abstract] [Full Text] [PDF] |
||||
![]() |
M Vennemann, T Bajanowski, T Butterfass-Bahloul, C Sauerland, G Jorch, B Brinkmann, and E A Mitchell Do risk factors differ between explained sudden unexpected death in infancy and sudden infant death syndrome? Arch. Dis. Child., February 1, 2007; 92(2): 133 - 136. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. W. Wang, R. R. Desai, L. Crotti, M. Arnestad, R. Insolia, M. Pedrazzini, C. Ferrandi, A. Vege, T. Rognum, P. J. Schwartz, et al. Cardiac Sodium Channel Dysfunction in Sudden Infant Death Syndrome Circulation, January 23, 2007; 115(3): 368 - 376. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Arnestad, L. Crotti, T. O. Rognum, R. Insolia, M. Pedrazzini, C. Ferrandi, A. Vege, D. W. Wang, T. E. Rhodes, A. L. George Jr, et al. Prevalence of Long-QT Syndrome Gene Variants in Sudden Infant Death Syndrome Circulation, January 23, 2007; 115(3): 361 - 367. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. S. Paterson, F. L. Trachtenberg, E. G. Thompson, R. A. Belliveau, A. H. Beggs, R. Darnall, A. E. Chadwick, H. F. Krous, and H. C. Kinney Multiple serotonergic brainstem abnormalities in sudden infant death syndrome. JAMA, November 1, 2006; 296(17): 2124 - 2132. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. F. Krous, E. A. Haas, J. M. Manning, A. Deeds, P. D. Silva, A. E. Chadwick, and C. Stanley Child protective services referrals in cases of sudden infant death: a 10-year, population-based analysis in san diego county, california. Child Maltreat, August 1, 2006; 11(3): 247 - 256. [Abstract] [PDF] |
||||
![]() |
American Academy of Pediatrics, K. P. Hymel, and the Committee on Child Abuse and Neglect, and National Association of Medical Examiners Distinguishing Sudden Infant Death Syndrome From Child Abuse Fatalities Pediatrics, July 1, 2006; 118(1): 421 - 427. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. L. Chadwick, H. F. Krous, and D. K. Runyan Meadow, Southall, and the General Medical Council of the United kingdom. Pediatrics, June 1, 2006; 117(6): 2247 - 2251. [Abstract] [Full Text] [PDF] |
||||
![]() |
G Ottaviani, L Matturri, R Mingrone, and A M Lavezzi Hypoplasia and neuronal immaturity of the hypoglossal nucleus in sudden infant death J. Clin. Pathol., May 1, 2006; 59(5): 497 - 500. [Abstract] [Full Text] [PDF] |
||||
![]() |
C Jenny and R Isaac The relation between child death and child maltreatment. Arch. Dis. Child., March 1, 2006; 91(3): 265 - 269. [Abstract] [Full Text] [PDF] |
||||
![]() |
Task Force on Sudden Infant Death Syndrome The Changing Concept of Sudden Infant Death Syndrome: Diagnostic Coding Shifts, Controversies Regarding the Sleeping Environment, and New Variables to Consider in Reducing Risk Pediatrics, November 1, 2005; 116(5): 1245 - 1255. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. P. Kiernan and R. C. Beckerman Is It Sudden Infant Death Syndrome or Sudden Unexpected Infant Death? Pediatrics, September 1, 2005; 116(3): 800 - 801. [Full Text] [PDF] |
||||
![]() |
L. B. E. Shields, D. M. Hunsaker, S. Muldoon, T. S. Corey, and B. S. Spivack Risk Factors Associated With Sudden Unexplained Infant Death: A Prospective Study of Infant Care Practices in Kentucky Pediatrics, July 1, 2005; 116(1): e13 - e20. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. M.L. Brotherton, B. P. Hull, A. Hayen, H. F. Gidding, and M. A. Burgess Probability of Coincident Vaccination in the 24 or 48 Hours Preceding Sudden Infant Death Syndrome Death in Australia Pediatrics, June 1, 2005; 115(6): e643 - e646. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. H. Malloy and M. MacDorman Changes in the Classification of Sudden Unexpected Infant Deaths: United States, 1992-2001 Pediatrics, May 1, 2005; 115(5): 1247 - 1253. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. H. Opdal and T. O. Rognum National Standard for Death-Scene Investigation of Sudden, Unexpected Infant Deaths in the United States: In Reply Pediatrics, March 1, 2005; 115(3): 823a - 824. [Full Text] [PDF] |
||||
![]() |
R. C. Beckerman Physiologically Redefining Bronchopulmonary Dysplasia Pediatrics, March 1, 2005; 115(3): 830a - 831. [Full Text] [PDF] |
||||
![]() |
M. H. Malloy SIDS -- A Syndrome in Search of a Cause N. Engl. J. Med., September 2, 2004; 351(10): 957 - 959. [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||