Epidemiology | Febrile convulsion

Epidemiology

A febrile spasm usually occurs in 2-5% of children between 6 months and 5 years of age, but mainly in the 2nd year of life. However, older children can also be affected: 15% of febrile convulsions occur between the ages of 4 and 8 years. In up to 40% of the affected children, a family history of febrile convulsions is observed, i.e. close family members also had febrile convulsions in childhood.

Therefore, a genetic predisposition of the child is considered to be a contributing factor in the body’s response to fever with a seizure. However, this does not mean that a sibling will necessarily also have febrile convulsions. In Europe and North America, about 2-5% of all children are affected by the occurrence of a febrile seizure.

A febrile seizure is a sudden cerebral seizure in combination with muscle twitches and a loss of consciousness, which can manifest itself in early childhood in conjunction with a febrile infection. The febrile convulsion is triggered by a violent and particularly rapid rise in body temperature. As a rule, it only occurs in children between 6 months and 5 years of age, as the child’s brain is particularly susceptible to seizures during this period of development.

The mean age peak for the occurrence of a febrile seizure is at the age of 14-18 months. Before the 6th month of life and after reaching the age of 5 years febrile convulsions occur less frequently. Statistically speaking, a febrile convulsion is a one-time event, and no pathological character is attributed to it at an age of 6 months to 5 years. Nevertheless, in rare cases it can also occur more frequently. In case of additional familial accumulation, a genetic cause is suspected in these rare cases.

Causes

Febrile diseases (infections), which are usually caused by a virus, act as a triggering factor for febrile convulsions. The most common diseases are inflammation of the middle ear (otitis media), three-day fever (exanthema subitum), a urinary tract infection in babies, gastroenteritis or a simple infection of the upper airways (e.g. bronchitis). Vaccinations against whooping cough (pertussis) or measles can also trigger febrile convulsions.Since the central nervous system (CNS) is not yet fully developed in small children, excessive electrical discharges can generally occur more easily in the brain than in adults, which manifest themselves in body spasms.

The elevated body temperature above 38°C during fever causes the nerve cells in the brain to become even more sensitive to unplanned discharges, which means that the threshold for triggering a seizure (convulsive threshold) is reached faster than normal. This can be imagined in such a way that the impulses that an active nerve cell otherwise only passes on in a certain direction are suddenly picked up by all surrounding neighboring cells and then the entire brain is activated by a chain reaction. Metaphorically speaking, this is similar to a “firework” in the brain, which causes all body muscles to twitch at the same time and one becomes unconscious.

The affected person then has a “seizure” or “epileptic seizure“. To trigger a febrile seizure, it is not crucial that the child has a particularly high fever, e.g. over 40°C, but rather the speed with which the temperature rises; even a moderate fever (38.5°C) can lead to a febrile seizure. In summary, febrile convulsions are caused by a sudden rise in fever in children with genetic predisposition during a phase of age-related lowered convulsive threshold.

Especially after combination vaccinations, a slight increase in body temperature may occasionally occur. This is the case with the MMR vaccination (mumps measles rubella) and the five-fold vaccination against diphtheria, tetanus, pertussis, polio and Haemophilus influenzae type b (DTaP-IPV-Hib). As a result, a slightly increased risk of fever attacks has now been demonstrated in a Danish study.

However, this is basically due to the slight fever and not to the actual vaccination. The risk is up to six times higher with the first and second five-fold vaccination. However, this percentage is deceptive, as it only affects about 5 children out of 100,000, as the basic risk of fever attacks is generally very low in the case of light fever.

It is therefore by definition a very rare side effect of vaccinations, which often has no further consequences. It is therefore not advisable to refrain from vaccination because of the fear of a fever attack. If the child has already had a febrile spasm, there is a risk of about 30-40% that it may recur.

This worries many parents, as they do not know whether they can still let their child sleep alone. Generally speaking, febrile convulsions tend to occur in the afternoon and evening. In addition, febrile convulsions are usually always accompanied by pre-existing fever.

If you now consider the few days of the year when the child has a fever and the percentage of febrile seizures that occur at night, you come to the conclusion that parents do not need to worry about their child having a seizure at night. Nevertheless, there is no reason why parents should not take their child into the bedroom when the fever is still present, just to be on the safe side. However, there is no great risk for the child.