Brief Resolved Unexplained Event (BRUE)

Article Author:
Noah Kondamudi
Article Editor:
Mumtaz Virji
10/27/2018 12:31:23 PM
PubMed Link:
Brief Resolved Unexplained Event (BRUE)


The American Academy of Pediatrics published a clinical practice guideline in 2016 recommending replacing the term apparent life-threatening event (ALTE) with a new term named brief resolved unexplained event (BRUE). An apparent life-threatening event was defined as any event that was frightening to the observer and consisted of a combination of apnea, color change, muscle tone change, and choking, or gagging. An apparent life-threatening event, which itself replaced the term near-miss sudden infant death syndrome (SIDS) in 1986, was regarded to be too imprecise for clinical practice and research due to its subjective and non-specific symptoms and causation by a wide range of disorders. Furthermore, this definition relied on the subjective report of the observer rather than on pathophysiology. The new label brief resolved unexplained event serves to remove the “life-threatening” label and better reflect the transient nature of the event and lack of a clear cause. 

The definition of a brief resolved unexplained event is an observed event occurring in an infant younger than one year of age where the observer reports a sudden, brief, yet resolved episode of one or more of the following:

  • Cyanosis or pallor
  • Absent, decreased, or irregular breathing
  • Marked change in tone (hyper- or hypotonia)
  • Altered level of responsiveness.

The diagnosis of brief resolved unexplained event can only be made when there is no explanation for a qualifying event after an appropriate history and physical examination.

Review of previous apparent life-threatening event literature reveals that a small subset of infants with a diagnosis compatible with a brief resolved unexplained event may have a serious underlying disease or are prone to recurrent episodes.

High-risk infants are those younger than two months of age, those with a history of prematurity (higher in less than 32 weeks gestation), and those with more than one event. Low-risk infants were those that are:

  • Age older than 60 days
  • Gestational age 32 weeks or older
  • Postconceptional age greater than or equal to 45 weeks
  • First brief resolved unexplained event (no previous brief resolved unexplained event ever and not occurring in clusters)
  • Event lasting less than one minute
  • No CPR required by the trained medical provider
  • No concerning historical features or physical examination findings.

Patients who do not meet criteria as low risk by default are considered high risk.


Implicit in the definition of brief resolved unexplained event is the word unexplained, indicating that there is no underlying cause. Nevertheless, infants in the high-risk category may have an underlying cause similar to those previously described in the apparent life-threatening event literature. These include gastroesophageal reflux, seizures, bronchiolitis, pertussis and child abuse. Other less frequent causes are inborn errors of metabolism, cardiac arrhythmias, increased intracranial pressure, toxic ingestions and syndromic conditions, especially those involving craniofacial anomalies.


Brief resolved unexplained event has been described only in 2016, and thus there are no reports describing the epidemiology. An apparent life-threatening event includes a subset of brief resolved unexplained events accounted for approximately 0.6% to 1.7% of all emergency department (ED) visits and 7.5% of calls to the emergency medical services (EMS) system for infants younger than one year of age. 


As brief resolved unexplained event is an unexplained event, pathophysiology of these events is unknown. However, the possible role of abnormalities in the swallowing mechanisms, in laryngospasm, in gastroesophageal reflux, and in autonomic function, are yet to be elucidated.

History and Physical

History and physical exam are essential to categorize the event as brief resolved unexplained event or to assign an alternate diagnosis. It is useful to ascertain the history with the clear focus on the circumstances before, during, and after the event. Features to be clarified before the event include the location of the event (home/daycare), whether the infant was awake or asleep, infant position (supine/prone, other), and activity (feeding, the presence of anything in the mouth, vomit/spit up). A thorough description of the event including if the infant was active or quiet, responsive or unresponsive, breathing, not breathing, or struggling to breathe, choking or gagging, appeared limp, rigid, or seizing, seemed distressed or alarmed, and change in skin or lip color (red, pale, blue). After the event, determine the approximate duration of event, abrupt or gradual termination, spontaneous termination or any interventions used (picking up, rubbing, CPR), behavior before return to normal (quiet, startled, fussy, or crying). Other useful information about recent illness, associated symptoms, history of illnesses especially apparent life-threatening event/brief resolved unexplained event, antenatal/perinatal history including gestational age, family history of early deaths especially, SIDS/apparent life-threatening event or presence of cardiac arrhythmias. Social history should focus on identifying the availability of social support systems and access to resources.

Infants presenting with brief resolved unexplained event are well and appear to have normal vital signs and physical exam findings. However, a thorough physical exam is required to identify those with high-risk brief resolved unexplained event or find the trigger to an alternate diagnosis.


Infants with a low-risk brief resolved unexplained event do not require any testing. A brief period of observation (one to four hours) with continuous pulse oximetry is adequate. The American Academy of Pediatrics does not offer any guidance for infants with high-risk brief resolved unexplained event; the common sense approach is to perform relevant tests based on specific areas of concern identified in the history or physical exam. Performing a 12-lead EKG can be considered as the benefit of identifying channelopathies that lead to sudden death and outweigh any harm. Testing for pertussis may be useful in the at-risk populations (suggestive symptoms, unimmunized patients). Other tests such as complete blood count, electrolytes, blood glucose, lactic acid, bicarbonate levels, blood gas, blood cultures, urine analysis, imaging, electroencephalogram (EEG), pH probe, and polysomnography are not routinely recommended.  

Treatment / Management

The key component of management is to educate caregivers about the condition, ensure close follow-up after discharge, and provide resources for training in cardiopulmonary resuscitation. Admission for cardiorespiratory monitoring is not routinely indicated. There is no role for medications, tests, specialist consultations, or home cardiorespiratory monitoring. Infants that are not low-risk should be managed based on the physiological status and abnormalities identified in history and physical exam.

Pearls and Other Issues

A few patients can present with brief resolved unexplained events like episodes that may not fit the definition. It is prudent that these infants be evaluated diligently and even be considered for hospitalization to facilitate a period of observation. Shared decision-making with caregivers should be part of the overall management strategy, especially in the face of a seemingly uncertain situation.