In a pallid BHS the brain sends a signal via the vagus nerve that severely slows the heart rate, leading to a temporary cessation of breathing and loss of consciousness.
Up to 17 percent of children with pallid BHS will experience syncope (fainting spells) as adults, usually in response to fear, injury, or emotional stress.
An electrocardiogram (ECG, EKG) that records the electrical activity in the heart may be used to check for heart rhythm abnormalities, such as long QT syndrome, in children who have had a pallid breath holding spell.
About 25 percent of affected children-particularly those who experience pallid BHS-have a family history of BHS or fainting.
The child cries or gasps, forcibly exhales, stops breathing, and turns either blue (cyanotic form) or pale (pallid form).