Reflex asystolic syncope

Reflex asystolic syncope, reflex anoxic seizures or RAS are a form of syncope encountered mainly, but not exclusively, in young children. Reflex anoxic seizures are not epileptic seizures or epilepsy. This is usually a consequence of a reduction in cerebral perfusion by oxygenated blood. It can be a result of either a sudden reduction in the blood flow to the brain, a drop in the oxygen content of the blood supplying the brain, or a combination of the two. Syncope can have different meanings ranging from transient loss of consciousness, usually accompanied by a decrease or loss in postural tone (the principal manifestations of “simple faints”), to tonic and myoclonic events and nonepileptic spasms.

A minor bump to the head is the most commonly reported precipitant. Usually the toddler trips and falls; the child's caregiver may hear the bump. Most commonly, the child does not cry, although some parents give descriptions of the child “trying to cry” (Stephenson 1978), or there may be a or a . Syncope rapidly ensues. Indeed the short latency between the stimulus and the attack has been emphasized as an important distinction from the more familiar (at least in older children and adults) vasovagal syncope. The child loses awareness and postural tone, falling to the ground. There may be down-beat nystagmus. The child is likely to be pale, sometimes described as “deathly white,” which is entirely appropriate given that they are likely to be asystolic; however, it is important to note that not all children go pale (or at least are perceived as going pale by their caregivers). Doctors have recorded descriptions from parents of “blue or purple lips,” “yellow patches through the blue,” and of no noticeable color change. In some attacks, the child rapidly returns to normal following the limp or pallid phase. However, more usually there is a convulsive phase. This is usually manifested with tonic stiffening, often amounting to opisthotonus, and often includes clenching of the jaw and hands. Video recordings of other forms of anoxic seizures (vasovagal syncopes) suggest that there may be marked asymmetry. Parents may report the eyes to have rolled or to be “popping out of the head.” A few clonic jerks of the limbs or spasms are often noted. Urinary incontinence is not uncommon. Any initial limpness may be so short that the whole attack is dominated by the convulsive components.

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