A Brief Resolved Unexplained Event (BRUE) is a medical classification for an alarming episode that occurs in an infant. This event prompts immediate medical attention because the observation is highly distressing to the caregiver. The classification represents a specific diagnosis made after a thorough medical evaluation, not merely a description of symptoms.
Defining a Brief Resolved Unexplained Event
The term BRUE was introduced by the American Academy of Pediatrics (AAP) in 2016 to replace the older, less precise term, Apparent Life-Threatening Event (ALTE). This classification is reserved for infants younger than one year who experience a sudden, brief, and resolved episode. The event must involve at least one of four specific signs: a noticeable change in color (pallor or cyanosis), a change in breathing (absent, decreased, or irregular patterns), a marked alteration in muscle tone (stiff or floppy), or an altered level of responsiveness.
To be classified as a BRUE, the episode must be “brief,” typically lasting less than one minute, and often only 20 to 30 seconds. It must also be “resolved,” meaning the infant returns completely to their normal baseline state of health without lasting effects by the time they are medically evaluated. Crucially, the event must remain “unexplained” after a comprehensive history and physical examination, as symptoms with an obvious cause (such as a fever or choking) are excluded from the diagnosis.
Prevalence and Statistical Likelihood
Determining the exact statistical likelihood of a BRUE is challenging because many mild events that resolve quickly and are not witnessed by a medical professional may go unreported. Based on population-level emergency department data, the incidence of BRUE is estimated to be approximately 4.28 per 1,000 live births. The incidence of the former classification (ALTE) was previously reported to be between 0.6 to 2.46 per 1,000 live births, suggesting BRUEs are a common pediatric problem.
The risk for a BRUE is not uniform across the first year of life, with the highest incidence occurring in the first few months. Infants under two months of age are disproportionately represented in cases brought to medical attention. Prematurity is another factor that increases an infant’s likelihood of experiencing such an event. These events account for a notable percentage of emergency department visits for infants under one year old.
Distinguishing Low-Risk and High-Risk BRUE
Following an event, the first step for a medical team is to quickly stratify the infant’s risk level to guide further evaluation and testing. The American Academy of Pediatrics established specific criteria to classify an infant as low-risk. An infant is considered low-risk only if they meet all the following criteria:
- They are older than 60 days of age.
- The event was the first one they have had.
- The event lasted less than one minute.
- No cardiopulmonary resuscitation (CPR) was performed by a trained provider.
The low-risk criteria also include specific gestational age requirements: the infant must have been born at 32 weeks gestation or later and have a postconceptional age of at least 45 weeks. If an infant fails to meet even one of these criteria, they are automatically classified as a higher-risk patient. In practice, a large percentage of infants evaluated after a BRUE, up to 87% in some studies, possess at least one higher-risk factor.
For infants classified as low-risk, the medical approach is conservative, often involving brief observation, focused history-taking, and a physical examination. Routine, extensive diagnostic testing, such as blood work or neuroimaging, is strongly discouraged for these patients because the yield is extremely low. Conversely, higher-risk infants, such as those with multiple events or a history of prematurity, require a more comprehensive and individualized evaluation to search for a potential underlying cause.
Long-Term Outcomes and Recurrence
The long-term outlook for infants who experience a BRUE is generally positive, especially for those classified as low-risk. Studies tracking low-risk infants have shown no increased risk of mortality or significant long-term developmental delays compared to the general population. Recurrence of a BRUE is relatively uncommon, with an overall recurrence rate estimated to be around 10%.
A common concern for parents is the potential link between a BRUE and Sudden Infant Death Syndrome (SIDS). Current medical consensus holds that BRUE is distinct from SIDS, and an isolated BRUE is generally not considered a precursor to SIDS. The two events have different risk profiles and distinct ages of peak incidence, with BRUE peaking earlier than SIDS. The formal BRUE classification helps medical professionals focus on immediate evaluation and management, providing reassurance about the typically benign nature of the event for most infants.