Definition
In the absence of infectious diseases affecting the central nervous system, febrile convulsions outline convulsive episodes, critical or otherwise, typical of children aged between 6 months and 6 years. Seizures in the course of febrile pathologies seem to be one of the most common neurological disorders of the pediatric age.
To be defined as such, a febrile convulsion must be triggered by a condition of hyperpyrexia (fever> 38 ° C *) during an extra-cerebral pathology (at least in appearance).
* 38 ° C: approximate minimum temperature rise to which we refer to hypothesize a possible manifestation of the febrile convulsion. It is right to point out that the minimum temperature rise we are discussing varies (and has changed) over time based on measurement methods, statistics and scientific societies. In the context of febrile convulsions, the 38 ° C value expresses the minimum body temperature value established by the American Academy of Pediatrics.
The observation of the child in the midst of a febrile seizure is often alarming and shocking for many mothers. Many women, looking at their child during a febrile seizure, fail to evaluate the convulsion with sufficient approximation: in similar circumstances, even a few seconds may seem like minutes. This parameter, as we will see in the course of the disquisition, is fundamental to hypothesize the possible compromise of the neurological activities of the child.
It is estimated that 2-4% of European children are affected by a form of febrile convulsion, whose peak incidence is observed around 18 months of age. However, the vast majority of febrile convulsions are harmless for the young patient, so it is very unlikely that a healthy child will sustain permanent injuries following a similar seizure.
Let us now examine the various forms of febrile convulsions, thus the causes, symptoms and available therapies.
Classification
Febrile convulsions can be distinguished in two macrogroups: simple forms and complex variants.
Simple febrile convulsions
To define themselves as "simple", febrile convulsions must depend on a generalized seizure * lasting less than 15 minutes. Generally, these variants occur in healthy children aged between 6 months and 6 years, with normal psychomotor development. In such circumstances, the cause lies in hyperpyrexia (fever), NOT in a CNS condition.
Simple febrile seizures do not recur more than once within 24 hours of the first episode. Affected children have a normal encephalogram and may have a certain genetic predisposition for febrile convulsions.
Complex febrile convulsions
Complex febrile convulsions are also called "high risk", since they can degenerate into epilepsy. Seizures can be focal **, partial or lateralized ***, lasting more than 15 minutes (a single episode) or 30 minutes (episodes repeated even within 24 hours). The target of febrile seizures can also be children younger than 6 months or older than 6 years. The encephalogram of these patients is generally altered (independently of the current or imminent convulsive crisis). Most affected patients have a positive family history of epilepsy and / or neurological abnormalities.
If a second febrile seizure occurs within the 15th minute of the administration of an anticonvulsant drug (used to treat the first seizure), the patient is almost certainly affected by the "complex" variant of febrile convulsions.
One speaks precisely of the state of febrile illness when the convulsion is prolonged for over 30 minutes or is characterized by multiple short seizures, without the restoration of the patient's consciousness. In similar situations, the crises are predominantly "clonic", and tend to occur at an age above 18 months.
Among the complex forms we also briefly mention unilateral febrile convulsions: these can last for a short time or for a long time. In the first case, it is possible that the child - generally suffering from pre-existing encephalopathy - may experience a post-critical, often transitory, hemiparesis ****. For unilateral and long-term complex febrile seizures, the patient may develop hemiplegia *****, post critical flaccid hemiparesis and epilepsy.
Glossary
Terminology
- Generalized crisis *: convulsive discharge affects both cerebral hemispheres. This particular convulsion is characterized by the bilateral nature of motor spasms. Generalized seizures are NOT necessarily subordinated to a cerebro-cortical focal pathology.
- Focal crisis **: typical manifestations of a distinct epileptogenic event within the cerebral cortex. Often, the manifestation of a focal crisis masks an underlying focal intracranial pathology
- Partial crisis / lateralized crisis ***: the crisis begins in a particular and circumscribed brain site. Often, therefore, these convulsive crises involve a precise cerebral portion of a single hemisphere
- Hemiparesis ****: obvious difficulty / inability to move a lateral part of the body
- Hemiplegia *****: total motor impossibility involving one half of the body, expression of a counter-lateral brain damage to the condition
In addition to the classification just reported, febrile convulsions can also be distinguished in other sub-categories, since the distinction between simple and complex forms is not always clear. Based on the "phenotypes", febrile convulsions are divided into:
- Early febrile seizures: appear within the child's 12 months of life
- Late febrile convulsions: they begin after the child's 6 years. They can persist even over 6 years
- Long-lasting febrile convulsions: the spasm lasts over 15-20 minutes
- Febrile convulsions with low fever: the crisis occurs in the presence of fever equal to 37.5-38 ° C
- Recurrent febrile convulsions: convulsive seizures often occur (almost) every episode of basal temperature alteration
- Afebrile convulsions: they occur without fever
- Febrile seizures associated with neurological diseases: seizures are caused by CNS problems
Febrile convulsions and epilepsy
There is no close correlation between neonatal / pediatric convulsions and the secondary development of a true epileptic form. It is estimated that the possible transformation occurs in a percentage between 25% and 56% of cases.
However, some risk factors that predispose the patient to epilepsy following a febrile convulsive event have been identified. Children of epileptic parents are more at risk of developing a form of epilepsy after a first episode of febrile convulsion. Even the presence of an early anomaly in psychomotor development could, in some way, favor the progression (in a negative sense) of the convulsive pathology.
It has also been documented how a particular correlation / concatenation of particular events can affect the degeneration of the febrile convulsion in epilepsy:
- Repeated febrile seizures occurring within 24 hours of the first seizure episode
- Duration of convulsion greater than 15 minutes
- Focal signs
- Ascertained transient neurological abnormalities
Child care
WHAT TO DO IF ...
- ... a child aged <18 months shows a first episode of febrile convulsions. In such situations, hospitalization is recommended. In some patients (suspected of meningitis or already being treated with antibiotics BEFORE the febrile convulsion) a lumbar puncture (rachicentesi) is necessary
- ... a child aged> 18 months has a first episode of febrile convulsions. In such circumstances, hospitalization may not be necessary IF the patient is stable and shows no signs or symptoms that require a diagnostic assessment. Parents must be carefully instructed on what to do.
- ... a child manifests a second simple febrile convulsion (in the context of a further febrile episode). Admission is not necessary. However, the possibility - albeit remote - of masking infectious diseases affecting the CNS should be considered.
- ... a child presents with complex febrile convulsions: hospitalization is necessary for the appropriate diagnostic tests.
