A Brief Resolved Unexplained Event (BRUE) describes a sudden, alarming episode in an infant that resolves completely on its own. This event causes significant anxiety for parents, often leading them to search for the worst-case scenario, particularly the risk of death. This article clarifies the actual risk associated with a BRUE, which is defined as an event for which no underlying medical cause is found after a thorough evaluation. The diagnosis is one of exclusion, assigned only after potential serious causes have been ruled out.
Defining the Brief Resolved Unexplained Event
The American Academy of Pediatrics (AAP) developed the term BRUE to replace the older, more alarming phrase “Apparent Life-Threatening Event” (ALTE) and to provide a more specific clinical definition. A BRUE is an episode occurring in an infant younger than one year of age that is reported by an observer as sudden, brief, and completely resolved. The event must have included at least one of four specific symptoms: a change in color (such as cyanosis or pallor), a change in breathing (such as absent, decreased, or irregular respiration), a marked change in muscle tone, or an altered level of responsiveness.
The episode must be brief, typically lasting less than 60 seconds. Critically, the infant must have returned entirely to their normal baseline state of health, with stable vital signs, at the time of medical evaluation. If an explanation for the event is found during the initial history and physical examination, the episode is not classified as a BRUE.
Risk of Mortality Following a BRUE Diagnosis
The diagnosis of a BRUE, particularly a “low-risk” BRUE, carries an extremely low risk of subsequent death, including Sudden Infant Death Syndrome (SIDS). Research shows no increased mortality risk following the event, which is considered a separate diagnosis from SIDS. A meta-analysis of studies involving thousands of infants found the risk of death after a BRUE to be approximately 1 in 800.
This calculated risk is considered roughly equivalent to the baseline risk of death for all infants during the first year of life. The excellent prognosis is strongly tied to the stratification of the event as “low-risk,” which is determined by specific criteria:
- The infant is older than 60 days.
- The infant was born at 32 weeks gestation or later with a corrected gestational age of at least 45 weeks.
- The first event lasted less than one minute.
- The event did not require cardiopulmonary resuscitation (CPR) by a trained medical professional.
An infant is classified as “higher-risk” if any of these criteria are not met, such as being under 60 days of age or having recurrent events. While higher-risk infants warrant more aggressive investigation, the BRUE diagnosis implies that the event resolved and no serious cause was identified in the immediate evaluation. For the vast majority of infants who meet the low-risk criteria, the outcome is favorable, supporting a management approach focused on reassurance and minimal intervention.
Medical Evaluation and Follow-up Care
The immediate medical response to a suspected BRUE focuses on a thorough history and physical examination to identify any underlying cause. Since BRUE is a diagnosis of exclusion, the evaluation searches for time-sensitive, serious conditions that could have caused the symptoms. For infants who meet the low-risk criteria, a conservative approach is often recommended, sometimes involving a brief period of observation in the emergency department with continuous pulse oximetry and cardiac monitoring.
Routine laboratory tests, such as blood work or specialized cultures, are generally not needed for low-risk patients. However, if the infant is classified as higher-risk, a more comprehensive diagnostic workup is initiated, which may include a 12-lead electrocardiogram (ECG), respiratory viral panels, and targeted blood tests. These infants may require hospitalization for observation, often for 12 to 24 hours, to monitor for event recurrence and to complete the necessary investigations.
Follow-up care for all BRUE patients includes parental education, especially on safe sleep practices and cardiopulmonary resuscitation (CPR) training. Parents of low-risk infants are typically advised to follow up with their primary medical doctor within a week of discharge. This comprehensive approach ensures that serious conditions are ruled out while minimizing the risks associated with unnecessary, invasive testing or prolonged hospital stays.
Underlying Conditions That Mimic BRUE
The intensive medical evaluation is necessary because many serious conditions can present with symptoms that look exactly like a BRUE. If a cause is found, the event is reclassified as a brief resolved explained event. Neurological conditions, such as seizures or central apnea, are common differential diagnoses that must be ruled out. Severe gastroesophageal reflux (GERD) with aspiration, which can cause color and breathing changes, is another frequent mimicker.
Infections are another category of concern, including conditions like pertussis, sepsis, or meningitis. Cardiac issues, such as congenital heart disease or arrhythmias like prolonged QT syndrome, must also be excluded, as they can cause sudden color and tone changes. If any of these conditions are identified, the event is not a BRUE, and treatment is focused on managing the specific underlying medical diagnosis.