Brief Resolved Unexplained Event (ALTE)

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Original Author(s): Dr Jennifer Mann and Dr Susanna Hodgkinson
Last updated: 11th August 2018
Revisions: 12

Original Author(s): Dr Jennifer Mann and Dr Susanna Hodgkinson
Last updated: 11th August 2018
Revisions: 12

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Brief resolved unexplained event (BRUE), or apparent life threatening event (ALTE), is defined as: ‘An episode that is frightening to the observer, during which a combination of the following symptoms are reported:

  • Apnoea
  • Choking or gagging
  • Colour change
  • Change in tone (1)’

These cases are difficult because you are often presented with a well looking child but a severely distressed parent, who has witnessed an event during which they thought their child was going to die. Careful history taking and examination may identify an underlying cause, although in 50% of cases the cause remains unknown.

In 2016, the American Academy of Paediatrics recommended that the term be replaced by BRUE (Brief Resolved Unexplained Event) to emphasise the transient nature and lack of clear cause for these episodes. This was also a move away from ‘life threatening’ terminology, which was worrying for parents and inaccurate, since studies had found no direct correlation with Sudden Infant Death Syndrome (SIDS) (2).  If a causative condition is discovered, this event is no longer defined as a BRUE – it is explained.

The full definition of a BRUE is: ‘An event occurring in an infant younger than 1 year when the caregiver reports a sudden, brief, and now resolved episode of ≥1 of:

  • Cyanosis or pallor
  • Absent, decreased, or irregular breathing
  • Marked change in tone (hyper- or hypotonia)
  • Altered level of responsiveness (3)’

Current guidelines focus on classifying patients into high and low risk groups to guide further management. The differential diagnoses and risk stratifying are discussed further below.


  • 1% of emergency presentations of infants less than a year old (4)
  • 2% of hospitalised children (4)
  • 6 – 5 per 1000 live births (5)
  • Mean age 8 weeks (2)
  • Seen more commonly in boys than girls


In 50% of patients a cause is identified, implying that there is a potential for intervention which could eliminate further events. GORD (Gastro Oesophageal Reflux Disease) is the most common cause – diagnosed in up to 31% of these patients (4).

The table below summarises the possible differential diagnoses, going from most common to rarer. The other 50% of ALTEs remain medically unexplained and are termed ‘idiopathic’ or defined as BRUE under the new definition. (6)

Aetiology Examples of conditions seen
Gastrointestinal GORD, swallowing problems, intussusception or volvulus
Neurological Head injuries, seizures or CNS infection
Respiratory URTI, pertussis (whooping cough), RSV, breath holding spells  or Obstructive Sleep Apnoea (OSA)
Cardiac Arrhythmias, prolonged QT interval, Wolff Parkinson White (WPW) Syndrome, congenital cardiac disease or vascular ring
Metabolic or Infective Inborn errors of metabolism, electrolyte disturbances (hypocalcaemia or hypoglycaemia)
Infective Meningitis and or sepsis
Child abuse Suffocation, shaken baby syndrome or Factitious Induced Illness (FII)
Toxins/drugs Accidental or non – accidental ingestion


Risk factors

  • Infants < 2 months old (3)
  • Infants under 30 days old are more likely to have a serious diagnosis or another ALTE (7)
  • Patients who were premature and have had multiple ALTEs are up to fourteen times more likely to have further ALTEs or serious underlying pathology (7)

Clinical features

Important areas to cover during history taking:

  1. Establish a clear description of the event itself

Often the patient will be asymptomatic upon arrival to the ED and history taking will rely upon the descriptions given by those who witnessed it – most likely the parents. Allow them to elaborate fully and then take time to ensure you can visualise a clear timeline of symptoms.

  1. Relation to feeding

A baby with reflux may hold its breath and arch its back after feeding and there may be associated vomiting

  1. Previous episodes

If there have been other episodes explore whether they presented with the same symptoms

  1. Sleep

Reflux tends to be worse when laid flat and parents may have tried elevating the head end of the cot, or find symptoms improve when the baby is held in a more upright position. Establish the sleeping arrangements including where the baby sleeps, bedding and clothing.

  1. Systems enquiry

Ask specifically about recent coryzal symptoms or URTI in the baby and family members. In the winter months, bronchiolitis is common and can present with apnoeas in younger babies.

  1. Past Medical History

Areas to be discussed here can be remembered using the BIND acronym:

Birth: In particular, prematurity puts the patient into a high risk category. If the baby required a stay on the Neonatal Intensive Care explore what this involved.


Nutrition / feeding: Find out the type of milk and volume given at each feed. The parents may have their red book which contain useful growth charts and health visitor reviews.

Development: Parents will usually be able to recall the age at which their child achieved various developmental milestones – particularly gross motor skills and speech. Delays in development may suggest an underlying neurological disorder.

  1. Family history

Ask specifically if anyone in the family has died at a young age or unexpectedly – cardiac arrhythmias and inborn errors of metabolism may present with sudden death.

  1. Social history

Non – accidental injury (NAI) can present as ALTE/BRUE. All families presenting to the ED should have a brief assessment for safeguarding risk factors – this is not a formal child protection assessment, unless indicated. It includes asking whether they are known to social services and if they have a named social worker, exploring in further detail where needed. You should also establish who lives in the family home.

Potential risk factors for NAI include story discrepancies between parents or only a single witness to the event, multiple events, previous sudden death in a sibling and exposure of the patient to adults with mental illness or substance abuse (7).  Social risk factors for NAI include negative attitudes towards the child, mental health problems, domestic violence, social services or police involvement and substance abuse.

If history taking reveals any safeguarding concerns, this should be escalated to senior staff.


During your examination, actively look for causes to exclude. This assessment should be detailed – examining each system in turn. Specifics to look for are as follows:


  • Vital signs – RR, HR, BP, oxygen saturations, temperature and responsiveness
  • Bedside blood glucose monitoring may also be appropriate
  • Growth – weight and head circumference
  • Dysmorphic features
  • Top to toe inspection for any bruises or skin marks suspicious of NAI

Respiratory including ENT:

  • Assess whether there are any signs of active upper or lower respiratory tract infection


  • Always feel the femoral pulse – this may be weak or absent in coarctation of the aorta
  • Listen carefully for any murmurs


  • Tenderness with a sausage shaped mass may be felt in intussusception
  • Always check the groin for hernias


  • The extent of the neurological examination will be dependent upon age, however even in the youngest of babies and most uncompliant of toddlers you should be able to make an assessment of the pupil responses and the limb tone and power.  If there are concerns of NAI, fundoscopy should be performed by an ophthalmologist to look for retinal haemorrhages.


In a review of diagnostic tests ordered in ALTEs, only 18% of tests were positive, and only a third of these contributed to a diagnosis (8). There is no evidence that routinely doing investigations is helpful unless there is clinical suspicion (7), since the prevalence of pathology is low and so false positives are common and complicate the picture.

Whereas in the past all these patients would have been investigated, the most recent guidelines recommend establishing whether the patient is high risk or low risk and using this to determine further investigation and management. Low risk features are:

  • Age > 2months
  • Gestational age >32 weeks
  • No previous BRUE
  • Event lasted < 1 minute
  • No CPR by healthcare professional
  • No concerning features in history or examination


Investigations for the low risk patient:

  1. ECG – A simple, non-invasive bedside test which will help exclude channelopathies, WPW or cardiomyopathy. Make sure you know how to calculate the corrected QT interval and document this clearly in the notes.
  2. Consider pernasal swab for pertussis – Whooping cough can present as life threatening apnoea in infants.


Investigations for the high risk patient:

ECG and pernasal swab for pertussis plus have a low threshold for performing the following tests:

  1. Chest X-Ray – It is not uncommon to have an abnormal CXR despite no focal chest signs
  2. Blood gas – May reveal a metabolic acidosis consistent with an inborn error of metabolism
  3. Lab bloods – Full blood count and film, urea and electrolytes, CRP, bone profile and glucose


Further invstigations may be appropriate depending on these results. For example if there is suspected sepsis, you will progress onto take blood cultures, urine culture and possibly lumbar puncture for meningitis. In cases of suspected inborn errors of metabolism, serum amino acids and ammonia samples (on ice) should be taken.


All parents who have witnessed such episodes will be understandably worried and need reassurance and therefore it is reasonable to observe all these patients for a period of time. This enables a duration of continuous oxygen saturation monitoring and vital sign recordings and also time to give a clear explanation to their parents. In infants, observation of a feed is also important if possible due to the prevalence of reflux.

For low risk patients, this period of observation may be performed in the emergency department or may require admission to the ward depending on hospitals individual protocols. Upon discharge, parents should be given:

  • Safety netting advice for what to do if future episodes occur
  • Formal Basic Life Support (BLS) training should be offered – this may mean organising for them to return to a planned session. Many studies recognise the benefits of offering caregivers this training–helping to alleviate caregiver anxiety, creating a sense of empowerment (3) and considered to be a useful skill for the community
  • Follow up in primary care should be considered. This may be a review by the health visitor or a GP depending on the case

For high risk patients, refer to the paediatric team for admission with investigations as previously discussed. The guideline recommends overnight oxygen saturation monitoring and serial vital observation recordings as a minimum.

If observations are stable overnight and investigation results normal, they can then generally be discharged home with advice and BLS training as per the low risk patients. If there are particular concerns, their named paediatric consultant may decide to organise outpatient follow up or consider home monitoring.


(1) American Academy of Pediatrics. National institutes of health consensus development conference on infantile apnea and home monitoring, Sept 29 to Oct 1, 1986. Pediatrics. 1987 Feb 1;79(2):292-9.
(2) Kiechl-Kohlendorfer U, Hof D, Peglow UP, Traweger-Ravanelli B, Kiechl S. Epidemiology of apparent life threatening events. Archives of disease in childhood. 2005 Mar 1;90(3):297-300.]
(3) Tieder JS, Bonkowsky JL, Etzel RA, Franklin WH, Gremse DA, Herman B, Katz ES, Krilov LR, Merritt JL, Norlin C, Percelay J. Brief resolved unexplained events (formerly apparent life-threatening events) and evaluation of lower-risk infants. Pediatrics. 2016 May 1;137(5):e20160590.
(4) McGovern MC, Smith MB. Causes of apparent life threatening events in infants: a systematic review. Archives of disease in childhood. 2004 Nov 1;89(11):1043-8.
(5) Romaneli MT, Fraga A, Morcillo AM, Tresoldi AT, Baracat EC. Factors associated with infant death after apparent life-threatening event (ALTE). Jornal de pediatria. 2010 Dec;86(6):515-9.
(6) Kahn A. Recommended clinical evaluation of infants with an apparent life-threatening event. Consensus document of the European Society for the Study and Prevention of Infant Death, 2003. European journal of pediatrics. 2004 Feb 1;163(2):108-15.
(7) Tieder JS, Altman RL, Bonkowsky JL, Brand DA, Claudius I, Cunningham DJ, DeWolfe C, Percelay JM, Pitetti RD, Smith MB. Management of apparent life-threatening events in infants: a systematic review. The Journal of pediatrics. 2013 Jul 31;163(1):94-9.
(8) Brand DA, Altman RL, Purtill K, Edwards KS. Yield of diagnostic testing in infants who have had an apparent life-threatening event. Pediatrics. 2005 Apr 1;115(4):885-93.



First draft: Dr Susanna Hodgkinson

Senior review: Dr Jennifer Mann