Brief Resolved Unexplained Event (Apparent Life-Threatening Event)



  • Brief resolved unexplained event (BRUE) is a term suggested by the American Academy of Pediatrics (AAP) to replace the term apparent life-threatening event (ALTE).
  • BRUE is a resolved episode in an infant <1 year of age that was sudden, brief, and characterized by any of the following:
    • Absent, decreased, or irregular breathing
    • Cyanosis or pallor
    • Marked change in muscle tone (hyper- or hypotonia)
    • Altered responsiveness
  • ALTE was originally described in 1986.
    • It disassociated apnea, color change, change in tone, choking or gagging with sudden infant death syndrome (SIDS), and triggered a research agenda for managing these patients.
    • It was faulted for including diagnoses such as choking or gagging, including actively symptomatic patients, and labeling an event as “life-threatening” without clear justification.
  • BRUE, by contrast, is used to describe a well-appearing patient with an event and symptoms that have resolved by the time of presentation to a medical practitioner.
    • Identifies low risk for recurrence or a serious underlying disorder based on:
      • Age >60 days
      • Born ≥32 weeks’ gestation and have corrected age ≥45 weeks
      • No CPR performed by trained medical provider
      • Event lasting <1 minute
      • First event
    • Offers management recommendations for lower risk patients


  • 43% of healthy term infants have at least one 20-second apneic episode over a 3-month period.
  • 5.3% of parents recall seeing apnea.
  • 0.2–0.9% of infants have an episode of apnea that results in an admission to the hospital.

Risk Factors

A greater risk for a future adverse event and/or serious underlying diagnosis is conferred by:

  • Prematurity and <45 weeks postconceptual age
  • Age ≤60 days
  • Multiple events
  • Events lasting >1 minute
  • CPR by trained medical provider
  • Suspected child maltreatment


No unifying pathophysiology because of the numerous potential presentations and underlying diagnoses

  • Central apnea: disrupted propagation of respiratory signals from the brainstem along the descending neuromuscular pathways. Example diagnoses with similar presentations include:
    • Apnea of prematurity
    • Congenital central hypoventilation syndrome
  • Obstructive apnea: neuromuscular respiratory effort disrupted by an occluded airway. Example diagnoses with similar presentations include:
    • Obstructive sleep apnea
    • Pierre Robin
  • Mixed apnea: combination of central and obstructive apnea. Example diagnoses with similar presentations include:
    • Laryngomalacia with a sedating ingestion
    • Prematurity with superimposed upper respiratory viral infection
  • Color change from decreased oxygenation or differential blood flow. Example diagnoses with similar presentations include:
    • Cyanotic heart disease
    • Acrocyanosis
  • Altered muscle tone from central or autonomic nervous system disruption. Examples include:
    • Seizure
    • Breath-holding spell
  • Altered responsiveness from effects on the cerebral hemispheres and/or reticular activating system. Example diagnoses with similar presentations include:
    • Toxic ingestion
    • Traumatic brain injury


By definition, a BRUE is unexplained. ALTE could have had multiple different etiologies or be labeled as idiopathic.

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