Reflex anoxic seizures (RAS) are paroxysmal, spontaneously reversing short-lived episodes of pronounced bradycardia or transient asystole which causes relative cerebral ischaemia, thereby inducing an anoxic ‘seizure’ or ‘attack’ (Martin 2010). The Founder Patron of the STARS (Syncope Trust and Reflex Anoxic Seizures) organisation Prof John Stephenson in 1993 aptly explained:
‘RAS is the term used for a particular fit which is neither epileptic nor due to cyanotic breathholding, but which rather results from a brief stoppage of the heart through excessive activity of the vagus nerve’ (STARS, 2012).
These events are usually triggered by a painful or frightening stimulus and often can be misdiagnosed as an epileptic seizure (Tidy, 2012). It is important that the paramedic team should remain aware of RAS as a differential diagnosis for a child presenting with an episode of sudden collapse.
Epidemiology and cause of RAS
RAS is also termed as white breath-holding and pallid infantile syncope (Martin, 2010). This occurs in all ages, the peak incidence is seen in children between the ages of six months and four years. RAS is seen more commonly in girls.
The most common trigger is an experience of sudden pain or fright, e.g. trapping a finger in a door or a minor blow to the head. Other triggers that might provoke RAS include mild febrile illnesses, venepuncture, exposure to excessively hot or cold baths, the sight of blood, a toy being snatched away by another child. The actual painful trigger pain may be trivial and often remains unnoticed by parents. (Warrington, 2004; Martin, 2010; Tidy, 2012).
RAS is thought to be caused by a neurally mediated syncopal event which follows a reflex asystole due to an increased vagal response (Martin, 2010; Tidy, 2012). In RAS, as the heart abruptly stops pumping blood for a couple of seconds (bradycardia), there is hardly any warning before loss of consciousness (Meyer, 2009; STARS, 2012). A prospective study with 380 children aged less than 16 years who were referred with ‘fits, faints, and funny turns’, syncope and RAS were demonstrated as the main causes for a nonepileptic spell (Hindley, 2006).
Clinical presentation
The painful physical or psychological stimulus is followed by a gasp or brief cry. The child will fall if he/she was standing and loses consciousness, appears pale and limp. Parents often describe their child as deathly white, ‘looking as though he/she was dead.’ The child may become stiff (tonic) and have jerking of the limbs (clonic). Upward deviation of eyes and urinary incontinence may also be seen. The episode is usually brief lasting <15 seconds but can last up to a minute (Warrington, 2004; Meyer, 2009; Martin, 2010; Tidy, 2012).
Recovery from RAC is often rapid, although the child can appear tired and washed out after regaining consciousness. This phase corresponds to the resolution of asystole (Warrington, 2004; Meyer, 2009; Martin, 2010; Tidy, 2012). It is important to remember that the child may suffer other injuries such as head injuries during the sudden collapse in RAS. An illustrative case study is described in Box 1.
Differentiating RAS from other serious causes
It is important to remember that RAS should be a diagnosis of exclusion made by paediatrician and these children should be carefully assessed before the diagnosis is made (Martin, 2010). An important differentiating criteria from epileptic events is that tongue-biting is not seen in children with a RAS (Tidy, 2012).
It has been found that that in up to 50% of cases of reported seizures by parents, a careful review of the history revealed that the presentation was more consistent with reflex anoxic seizures than an epileptic event (Stephenson, 2001; Tidy, 2012). The other differential diagnosis would include other causes of childhood syncope such as breath holding spells (blue syncope), neurally mediated syncope, cardiovascular causes, arrhythmias, reflex syncopes, non-cardiovascular pseudo-syncopes, and psychogical causes (Stephenson, 2001; Tidy, 2012).
Management
Paramedic teams are often requested to attend such emergencies when a child suddenly collapses, RAS should always be considered as a possible cause.
The initial management should follow the ABCDE approach (A=Airway, B=Breathing, C=Circulation, D=Disability (include blood glucose) and E=Exposure). A focused history would indicate the cause. However, it is important that the child is brought to the hospital after the first episode of RAS for proper assessment and diagnosis. Subsequent episodes of RAS in a child who has an established diagnosis may be managed at home with an assessment and reassurance from the paramedic team.
Paediatric assessment should include a detailed history and examination and in most cases this is enough to establish a diagnosis of RAS. However, in some cases where the history is not clear or the trigger remains unwitnessed or there is a strong suspicion about an epileptic seizure, an ECG (electrocardiogram) and EEG (electroencephalogram) may be done (Martin, 2010; Tidy, 2012). Both the investigations would be found as normal in RAS.
Paramedic teams should avoid administering anticonvulsants to a child who has already been diagnosed with RAS during subsequent episodes. However, it is important that the paramedic team assess the child thoroughly following the episode of RAS to rule out other injuries that may have occurred during the episode of RAS; the need for this is clearly demonstrated in case study (see Box 1). It is important that the parents are provided with an explanation about RAS and reassurance is given to the child and parents. Parents should also be advised to place the child in the recovery position; monitor the child and avoid picking up the child during or immediately after an episode.
In severe cases, pacemaker insertion has been shown to be very effective (Martin, 2010; Tidy, 2012). Most children grow out of RAS but persistence/recurrence in later life may be found in few cases (Martin, 2010).
Conclusions
RAS is common in childhood and may get misdiagnosed as epilepsy. Parents will be extremely worried after the event and needs a lot of reassurance. Paramedic teams should assess and may manage a well child with an established diagnosis of RAS at home. Other associated injuries should be actively sorted after an episode of RAS. The condition is benign with a good prognosis.