After approximately 30 seconds of apnea, a color change is apparent as children become cyanotic. The spell may terminate at this point, or children may proceed to lose consciousness and become limp. Some physicians refer to attacks that terminate prior to the loss of consciousness as simple BHS, whereas others do not classify such episodes as BHS at all. Rarely, loss of consciousness may be followed by a few seconds of rhythmic clonic jerking of the extremities, mimicking seizure-like activity, or rigid opisthotonic posturing of the body. The entire attack lasts less than one minute.
Children generally resume full activity within a few minutes.
Unlike the post-ictal period of epileptic seizures, prolonged periods of lethargy or drowsiness following spells are uncommon. Pallid spells are similar to cyanotic BHS with some exceptions. In pallid BHS, children often lose consciousness or tone after only a single gasp or cry, whereas in the cyanotic form, the period of apnea prior to loss of consciousness is much longer. Although the spells are triggered by identifiable stimuli, they are involuntary. It is believed that loss of consciousness in both forms is caused by cerebral anoxia.