Feverish convulsion: definition
More than a single clinical entity, febrile convulsions constitute a syndromic variant that groups together different types of simple and / or epileptic seizures. Despite the odds that a child affected by a febrile seizure develops epilepsy is rather scarce, medical advice and, possibly, hospitalization are always essential.
Today, thanks to the improvement of diagnostic and therapeutic techniques, febrile convulsions must be considered a benign form, which is well distinguished from epilepsy. It is worth pointing out again that the consequences of a single episode of febrile convulsion (or even more attacks spaced over time) are scarce, almost nil. In fact, in the absence of CNS changes, simple febrile seizures do not increase the risk of death, brain damage or mental retardation.
In this article, febrile seizures are analyzed in terms of symptoms, diagnosis and therapy. Let's see in more detail.
Causes
The target of febrile convulsions is represented by healthy children aged between 6 months and 6 years, although statistical surveys also document younger infants and older children suffering from the same disorder.
The vast majority of febrile seizures occur within 24 hours of a sudden fever (> 38-38.5 ° C). Ear diseases (eg otitis), as well as any pathology with a viral or bacterial etiology (eg rubella, sixth disease, flu, etc.) can expose the child to the risk of febrile convulsions.
Some sporadic cases of febrile convulsions have been reported as a result of much more serious pathologies, such as encephalitis or meningitis: in similar situations, the child's condition can degenerate within a short time, since we are faced with an involvement of the central nervous system .
- However, remember that similar diseases can cause seizures even in the absence of fever.
A certain correlation between some vaccinations and the outbreak of a febrile convulsion has been documented. Some vaccines - such as those for tetanus-diphtheria-pertussis or those for measles-mumps-rubella - seem to expose the child to the risk of febrile convulsion. In similar situations, spastic crises are due to fever (a typical side effect of vaccination in the newborn) and NOT to the vaccine itself.
The pathogenesis of febrile convulsions is not completely understood: however, it seems that a mix of age, environmental factors and genetic predisposition is heavily involved.
Deepening: Genetic predisposition and febrile convulsions
Although it is established that familiarity plays a major role in the etiopathogenesis of febrile convulsions in children, the precise mode of transmission has not yet been demonstrated. Some hypotheses have been formulated: it seems that the disorder can be transmitted through a complicated autosomal-dominant, autosomal recessive or polygenic mechanism. Thanks to numerous linkage studies, it was possible to identify 4 gene loci: FEB1, FEB2, FEB3 and FEB4. These linkage studies allow to identify the precise chromosomal position of a locus responsible for a given genetic disease: it is a useful approach for the determination and mapping of some genes responsible for genetically transmitted diseases.
Risk factors
A certain correlation has been observed between the incidence of febrile convulsions and some risk factors. The most vulnerable subjects from this point of view are:
- premature babies
- children with HSV-6 infections (Herpes virus type 6)
- children affected by viral infections in general
- children with family members with a history of febrile convulsions
Clearly, CNS disorders also predispose the patient to febrile convulsions.
In addition to these newly listed risk factors, other elements predisposing to the recurrence of febrile convulsions have been identified. In fact, some pediatric patients tend to develop other febrile seizures after the first crisis; the recurrence of these episodes is favored by some risk factors:
- The first seizure occurred within the child's 6-12 months of life. In this case, it is very likely that the small patient develops new convulsive seizures within a year of onset
- The first episode of febrile convulsion is induced by a relatively low fever (<38 ° C)
- The duration of the first seizure lasts over 15 minutes
- Genetic predisposition
- Concomitant critical events during the first seizure
Common symptoms
The symptoms that characterize febrile convulsions vary according to the severity of the disease. In most affected children, the febrile convulsion begins with the "rolling" of the eyes and with the stiffening of the limbs. Subsequently, the child loses consciousness and, involuntarily, contracts and repeatedly relaxes the muscles of the lower and upper limbs. During this phase the loss of control of the anal and bladder sphincters is not uncommon. Febrile convulsions, causing breathing difficulties, can induce a cyanotic state in the child.
When the febrile seizure lasts more than 10-15 minutes, the child may also experience severe respiratory problems, extreme sleepiness, vomiting and stiff neck.
The occurrence of multiple episodes of febrile convulsion in the context of a single viral disease must be considered a serious medical urgency.
investigations
The diagnosis of febrile convulsion is considered relatively simple. The investigation is placed following the story of the critical episode (almost never observed by a doctor!) And subsequently confirmed by a neurological examination.
In healthy children, the neurological examination may be repeated to deny the hypothesis of a possible - even if unlikely - involvement of the central nervous system. In case of suspected CNS damage (eg severe infections, meningitis, concomitant neurological diseases), lumbar puncture (rachicentesi) is recommended, to always be performed after a CT scan or an RMN.
The differential diagnosis with febrile syncope is important.
No specific laboratory tests are indicated for diagnostic confirmation.
The encephalogram (known to most with the acronym EEG) of a child suffering from a single episode of febrile seizure is usually normal. If the fever has not yet dropped, it is recommended NOT to subject the small patient to this diagnostic examination: the alteration of the basal temperature could alter the test.
Some authors are convinced that the EEG in a healthy child is not indispensable for the diagnosis of a febrile convulsion, since in the vast majority of cases (if not almost all) it is normal. Other researchers believe instead that the EEG - following the convulsive febrile event - is fundamental to have a further denial of the possible damage to the CNS. Recall that the EEG exam is able to reveal specific or non-specific intercritical abnormalities in an early and often unequivocal way.
therapies
In most cases, febrile convulsions constitute a self-limiting event: in the absence of pre-existing brain damage, the prognosis of febrile convulsions is excellent, therefore no specific treatment is necessary.
Contrary to common thinking, it is not essential to immediately lower a fever to stop a febrile crisis. Therefore, it is strongly NOT recommended to administer antipyretics through the mouth during a seizure: the child would risk choking. For the same reason, it is recommended not to immerse the child in cold water. Most febrile seizures resolve themselves in a couple of minutes, with no brain damage to the child.
The clinical picture takes on a more serious significance in the event that the convulsive crisis lasted more than 15 minutes: in this case, the febrile convulsion is a medical emergency in all respects. In such circumstances, the doctor will administer specific rectal or intravenous medications to stop the seizure. The most widespread treatment consists of rectal administration of benzodiazepines (eg diazepam): these powerful drugs interrupt the convulsion, therefore the crisis in progress.
Clearly, after treating the main symptom (convulsion) it is necessary to proceed with the cure of the illness that has triggered the whole.
Prognosis
The SHORT-TERM prognosis concerns the relapsing forms of febrile convulsions.
In general, following a first febrile convulsion, the risk of reappearance is estimated at around 10%. This data just reported is influenced by the age of onset of the crisis, the extent of fever and underlying diseases. The risk increases up to 25-50% in conjunction with one or two risk factors (eg genetically predisposed subjects, appearance of the first crisis before 6 months, etc.), up to 50-100% in the child with more than three risk factors.
The LONG-TERM prognosis defines the risk of degeneration of the convulsive crisis in epilepsy proper.
From what is reported in the scientific journal BJM journal ( Clinical research ed .), It appears that the probabilities of developing epilepsy increase in conjunction with:
- complex febrile convulsions
- neurological abnormalities
- family predisposition
- manifestation of the convulsion less than an hour after the outbreak of fever.
In the absence of the aforementioned characteristics, 2.4% of children with a previous history of febrile convulsions are at risk of epilepsy.
The administration of phenobarbital and sodium valproate was totally INEFFECTIVE to prevent the degeneration of febrile convulsions in the context of epilepsy. We also remember the side effects related to the immoderate use of these medicines, linked in particular to the cognitive sphere.
Prevention of recurrences
Continuous prophylactic treatment with antiepileptic drugs for the prevention of recurrent febrile convulsions is strongly discouraged.
The so-called "intermittent" prophylaxis of recurrent convulsions with benzodiazepines is possible in some specific cases (eg very early onset age, very frequent relapses, pre-existing neurological deficits etc.). The drugs most commonly used for this purpose are phenobarbital and sodium valproate.
Instead, the preventive treatment of hyperthermia is recommended: the sponging of water, the temporary application of ice on the head and the administration of antipyretics every 4-6 hours (in the case of a basal temperature above 37.5 ° C) are particularly useful for keeping fever under control, especially in children predisposed to febrile convulsions.
