What are the definition criteria for Brief Resolved Unexplained Events (BRUE)?

BRUE Definition Criteria

A Brief Resolved Unexplained Event (BRUE) is diagnosed in infants younger than 1 year when an observer reports a sudden, brief (lasting <1 minute, typically 20-30 seconds), and now completely resolved episode that includes at least one of four specific clinical features—and critically, remains unexplained after thorough history and physical examination. 1

Core Diagnostic Criteria

The diagnosis requires all three of the following components 1:

1. Age Requirement

• Infant must be <1 year of age 1
• This strict age limit distinguishes BRUE from the older ALTE terminology 1

2. Event Characteristics: Brief and Resolved

• Duration: <1 minute (typically 20-30 seconds) 1
• Completely resolved: infant has returned to baseline state of health 1
• The event must be sudden in onset 1

3. Clinical Features: At Least ONE of the Following Four

The observer must report ≥1 of these specific findings during the event 1:

• Cyanosis or pallor (not rubor/redness, which is normal in healthy infants) 1
• Absent, decreased, or irregular breathing (includes obstructive apnea, mixed apnea, or other breathing irregularities) 1
• Marked change in tone: either hypertonia or hypotonia 1
• Altered level of responsiveness (may include loss of consciousness, mental status change, lethargy, somnolence, or postictal phase) 1

Critical Exclusion Criterion: "Unexplained"

BRUE is a diagnosis of exclusion—you can only diagnose BRUE when there is no explanation for the qualifying event after conducting an appropriate history and physical examination 1, 2. This is what fundamentally distinguishes BRUE from other diagnoses.

Events That PRECLUDE BRUE Diagnosis

The following findings mean the event is NOT a BRUE 1:

• Fever 1
• Respiratory symptoms (nasal congestion, increased work of breathing suggesting viral infection) 1
• Choking after vomiting or feeding (suggests gastroesophageal reflux) 1, 3
• Any identifiable cause found on history or physical examination 1

Essential Historical Features to Assess

To determine if an event qualifies as "unexplained," you must systematically evaluate 1:

Event Details

• Who witnessed the event and reliability of historian 1
• Infant's state immediately before: awake/asleep, position (supine/prone/upright), feeding status 1
• During the event: choking/gagging sounds, active/flaccid, conscious/unresponsive, breathing pattern, skin color (specifically cyanosis or pallor, not just "color change"), bleeding 1
• Event termination: spontaneous resolution vs. intervention required (picking up, positioning, back blows, CPR) 1
• Approximate duration 1

Red Flags for Child Abuse

• Multiple or changing versions of history 1
• History inconsistent with developmental stage 1
• Unexplained bruising 1
• Previous child protective services involvement 1

Medical and Family History

• Family history of sudden unexplained death in first- or second-degree relatives before age 35, particularly in infancy 1
• Family history of Long QT syndrome or arrhythmias 1
• Prior similar events in the patient or siblings 1
• Prematurity (gestational age and postconceptional age) 1
• Developmental concerns 1
• Recent infectious exposures (particularly pertussis, upper respiratory illness) 1

Required Physical Examination Components

A thorough physical examination is mandatory to exclude identifiable causes 1:

• General appearance: craniofacial abnormalities (mandible, maxilla, nasal), age-appropriate responsiveness 1
• Growth parameters: length, weight, head circumference 1
• Vital signs: temperature, pulse, respiratory rate, blood pressure, oxygen saturation 1
• Skin: color, perfusion, evidence of injury (bruising, erythema) 1
• Head: fontanelles, bruising or other injury 1
• Eyes: extraocular movements, pupillary response, conjunctival hemorrhage, retinal examination if indicated 1
• Nose/mouth: congestion, blood, evidence of trauma, torn frenulum 1
• Chest: auscultation, rib tenderness, crepitus 1
• Cardiovascular: rhythm, rate, murmurs 1
• Abdomen: organomegaly, masses, tenderness 1
• Neurological: tone, responsiveness 1

Risk Stratification After BRUE Diagnosis

Once you've confirmed the event meets BRUE criteria, stratify into lower-risk vs. higher-risk 1:

Lower-Risk BRUE Criteria (ALL must be met)

• Age >60 days 1
• Gestational age ≥32 weeks AND postconceptional age ≥45 weeks 1
• First BRUE (no prior events, not occurring in clusters) 1
• Event duration <1 minute 1
• No CPR by trained medical provider 1
• No concerning historical features 1
• No concerning physical examination findings 1

Higher-Risk Features

Any infant not meeting all lower-risk criteria is classified as higher-risk 1, 4, 5:

• Age <60 days (infants <2 months consistently show higher risk) 1
• Prematurity (<32 weeks' gestation or <45 weeks' postconceptional age) 1, 4
• More than one event or events occurring in clusters 1, 4
• Event duration ≥1 minute 1
• CPR required by trained medical provider 1
• Concerning history or physical examination findings 1

Common Pitfalls to Avoid

• Do not diagnose BRUE based solely on caregiver perception that the event was "life-threatening"—the diagnosis requires objective clinical characterization 1
• Episodes of rubor (redness) are NOT consistent with BRUE—they are common in healthy infants 1
• Do not classify events with vomiting-related choking as BRUE—this suggests GER and provides an explanation 1, 3
• Acrocyanosis (bluish discoloration limited to hands/feet) in newborns is physiologically normal and should not be confused with the cyanosis criterion for BRUE 6
• Central cyanosis is never normal and requires immediate evaluation—if present, the event is explained and not a BRUE 6
• Be alert for seizure activity: assess for tonic eye deviation, nystagmus, tonic-clonic movements, or infantile spasms, which would explain the event 1, 3