Hyperthermic seizures or febrile convulsions are involuntary neurological manifestations occurring during an episode of fever. Impressive but mostly benign, they affect children between 6 months and 5 years old. Symptoms, causes, treatments… Dr. Hélène Maurey, pediatrician specializing in neurology, tells us all about hyperthermic convulsion.

“Hyperthermic convulsions are epileptic seizures that occur against a background of fever. They affect 2 to 5% of children aged 6 months to 5 years, with a peak onset between 1 and 3 years ”, specifies the pediatrician. 

These are convulsive attacks that occur during an episode of fever, that is to say a temperature of at least 38 ° C. The main symptoms are: 

• loss of consciousness. 
• most often a generalized stiffness. 
• involuntary and symmetrical muscle contractions, the whole body is affected (both arms and both legs).  
• eye revulsion or staring.
• sometimes a change in the color of the lips and face (paleness, redness or blue lips).

After the seizure, the child then goes through a recovery phase during which he may be drowsy, hypotonic and breathing hard. Then everything returns to normal within minutes of the end of the seizure.

In febrile convulsions, we distinguish simple seizures from complex seizures. Simple seizures are short, usually lasting between 5 and 15 minutes, most often less than 5 minutes, and the twitches are symmetrical. While complex seizures are longer, greater than 15 minutes, repeat throughout the day and are focal. “This means that the twitching and muscle stiffness only affects one side of the body. Also, the child victim of a complex crisis may have difficulty recovering at the end of the crisis and suffer from transient paralysis ”, adds the specialist.

It is a multifactorial disorder. Hyperthermic convulsion is caused by a fever characteristic of an infection often related to a virus. “Young children are more vulnerable to viruses and microbes – to which they are more exposed than adults – because they create immunity for themselves,” says Dr Maurey. Be careful, contrary to what one might think, the fever does not have to be high to cause a crisis, it can be mild. It is not the number that counts but simply the occurrence of a fever, even a slight one. 

If these seizures affect children and not adults, it is because their brain, still immature, has a lower seizure threshold when faced with an event including fever. and the inflammation it generates. 

The occurrence of febrile convulsions would also have a genetic origin in a third of cases. If a child has a close relative (father, mother, brother or sister) who has already had several episodes of hyperthermic convulsion as a child, he is more likely to suffer from it in turn. 

Rest assured, febrile convulsions are not a sign of a neurological problem and therefore have nothing to do with epilepsy. Likewise, the crisis is most often unique (in 70% of cases). It is estimated that 30% of children who have had an episode of seizure are likely to have it again during other episodes of fever.

“Easy to say, but above all, don’t panic!” Insists the pediatrician. The first thing to do is to secure the child’s environment so that he does not injure himself: “we remove the objects around him or which could be in his mouth, then we install him in a lateral safety position to free the airways or prevent him from choking on vomiting ”. Do not try to prevent the child’s movements or put the tongue out of his mouth. 

Then there is nothing else to do except wait for the crisis to end by staying with the child. Note that most seizures last less than 5 minutes. Impressively, hyperthermic seizures often cause parents to call the 15th, which is legitimate when it is a first episode. But you should know that this is not essential when the crisis lasts less than 5 minutes and the child recovers in less than 10 minutes. However, you must immediately call 15 or 112 if:

• The child is less than 6 months old or more than 5 years old. 
• The child does not have a fever.
• The convulsions are repeated within 24 hours.
• Seizures are not symmetrical (they affect only one side of the body).
• The seizure lasts more than 5 minutes and the child has difficulty recovering afterwards. 
• The child has breathing difficulties.
• The child has a known neurological disease. 

These signs are characteristic of complicated seizures, which are rarer, but which should be watched closely as they may be a symptom of an underlying disease. 

If the parent (s) have not contacted the emergency services, it is however obligatory to consult the attending physician or pediatrician in the days following the crisis to check the child’s health, find the cause of the fever and treat it quickly.

Treatment consists of find the source of the fever to treat it (otitis, nasopharyngitis, chickenpox…). “If the crisis lasts more than 5 minutes, the emergency services alerted and arriving on the spot can possibly administer benzodiazepines to the child rectally or endo-buccally”, specifies the pediatrician. 

In the event of a so-called “complicated” crisis, additional examinations are carried out (scanner, blood test, lumbar puncture, etc.).

No, we cannot prevent seizures but it is possible to define the risk of recurrence. “It is estimated that the risk of recurrence is 80% if the child has more than three following criteria: 1st degree family history of febrile seizures; the seizure occurred early in the fever episode, that is, hours after the onset of the fever; the seizure occurred before the age of 15 months; a low fever. In the absence of these criteria, the risk of recurrence is estimated at 10% ”, reports Dr Maurey.

These crises are mostly benign, they leave no after-effects in the child. “Particular vigilance must however be brought to children who have a prolonged crisis, more than 20 to 30 minutes”, warns the specialist in pediatric neurology. 

The hyperthermic crisis still represents a small trauma for the family because witnesses may have the impression that the child is dying. “Even if it is nothing serious, the febrile seizure is very impressive for the parents. This is why the doctors who collect their testimony should not hesitate to take the time to explain to them the causes of the appearance of these crises and to reassure them as much as possible. The doctors know that these crises are not serious, but the parents are not ”, insists the pediatrician.