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Sudden Unexplained Death in Childhood

NORD is very grateful to Henry F. Krous, MD, Clinical Professor of Pathology and Pediatrics at the University of California, San Diego and Rady Children's Hospital-San Diego for the preparation of this report.

Synonyms of Sudden Unexplained Death in Childhood

  • SUDC

Disorder Subdivisions

  • No subdivisions found.

General Discussion

Sudden unexplained death in childhood (SUDC) is defined as the sudden death of a child greater than one year of age that remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history.

SUDC deaths have occurred at the following sites:

Death at home, history provided: 79%
Crib or bassinet: 54%
Adult bed: 36%

The placed and found positions were as follows:

Placed supine, side, prone*: 10%, 2%, 3%
Found prone: 89%
Found face position: down, side: 10%, 8%
Co-sleeping, sweating when found: 3%, 1%

*applies only to youngest children


Nearly all of the children with SUDC were thought to be sleeping before becoming unresponsive. The older children who died of SUDC were more likely to have clinically recognizable but nonspecific symptoms before their deaths.

The seizure history among the cases and their families is noteworthy:

Child seizure history: 31%
Febrile seizures: 80%
Family seizures history: 37%
Febrile seizures: 57%
Child & family seizure history: 26%


The causes of SUDC are unknown. However, several studies have now established that SUDC is characterized by a frequent history of seizures that are usually associated with a fever in the affected child and their family members as well as occasional histories of irritability, excessive crying, vomiting, and histories of recent minor head trauma. Detailed neuropathologic studies have identified a subset of children with abnormal development of the hippocampus. It has been proposed that they represent a group of SUDC cases whose sudden death was caused by an unwitnessed seizure arising during sleep in the anomalous hippocampus and producing cardiopulmonary arrest. Fever, infection, and/or minor head trauma may be the precipitating factors that cause the seizure and it appears that a history of febrile seizures and/or a family history of febrile seizures are important risk factors.

A recent study tested the hypothesis that a SUDC subset is characterized by hippocampal maldevelopment and an individual and/or family history of simple familial seizures. The study concluded that a potential new entity may account for the majority of SUDC in toddlers, defined by sleep-related death in the prone position, individual/family history of febrile seizures, and hippocampal anomalies. The mechanism of death appears analogous to sudden death in (temporal lobe) epilepsy (SUDEP), with a putative unwitnessed seizure during sleep leading to airway occlusion and death. This study mandates further research into the potential link between simple febrile seizures and death.

Affected Populations

Children who die of SUDC are generally toddlers between 1 and 4 years of age, but older children have been uncommonly affected. Nearly 80% have been less than 3 years of age. Approximately two thirds of the cases are males. A predilection for a particular ethnic group has not been established. Nearly 90% are born at term and nearly half are first born. Nearly six percent of the cases are part of a multiple birth gestation.

Related Disorders

Symptoms of the following disorder can be similar to those of SUDC. Comparisons may be useful for a differential diagnosis.

Sudden death in (temporal lobe) epilepsy (SUDEP) is defined as sudden, unexpected, nontraumatic, nondrowning death in an individual with epilepsy, witnessed or unwitnessed, in which the postmortem examination does not reveal an anatomical or toxiclogical cause for the death. These deaths are not thought to be the direct result of a seizure, but often occur after a recent seizure. Factors that are thought to be related to SUDEP include respiratory events such as airway obstruction, apnea and neurogenic pulmonary edema, cardiac arrhythmias, and subtherapeutic levels of antiepileptic medications.

Standard Therapies

SUDC is a diagnosis of exclusion which means that it is only determined as the cause of death after thorough investigation of the clinical history, scene of death and autopsy reveal no other cause. Because the diagnosis of SUDC is made after death, there is no treatment.

Investigational Therapies

Information on current clinical trials is posted on the Internet at All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010

For information about clinical trials sponsored by private sources, contact:

Sudden Unexplained Death in Childhood Resources



Kinney H, Chadwick A, Crandall LA, et al. Sudden Death, Febrile Seizures, and Hippocampal Maldevelopment in Toddlers: A New Entity. Pediatr Dev Pathol. 2009:1.

Kinney HC, Armstrong DL, Chadwick AE, et al. Sudden death in toddlers associated with developmental abnormalities of the hippocampus: a report of five cases. Pediatr Dev Pathol. 2007;10:208-223.

Krous HF, Chadwick AE, Crandall L, Nadeau-Manning JM. Sudden unexpected death in childhood: a report of 50 cases. Pediatr Dev Pathol. 2005;8:307-319.

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Report last updated: 2010/04/28 00:00:00 GMT+0

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