Febrile convulsions describe a seizure experienced by a pediatric patient whose body temperature is pathologically elevated. Most affected children are between 6 months and 5 years of age and in the vast majority of cases, febrile convulsions do not precede epilepsy in later life.
Anamnestic data are of major importance to identify FC and to avoid confusion with more severe disorders and any type of epilepsy. Although FC often occur repeatedly, a history of seizures that have not been related to a febrile illness is untypical for this disease. In most cases, fever and possibly additional symptoms associated with the underlying disease are the only pathological findings in FC patients. Of note, cerebral trauma may in certain circumstances cause manifestations similar to FC . These may or may not be related to pathological findings obtainable by physical examination.
First FC are often registered within the first day after fever sets in.
Simple febrile seizures are more common than complex febrile seizures. The former last up to five minutes and the patient fully recovers within an hour after symptom onset. The affected child does not show more than one episode of FC per day. Generalized clonic seizures are most typical, but tonic and even atonic fits have also been observed. Apart from the above-described conditions, these children are healthy.
Status epilepticus, focal seizures, more frequent convulsions and a considerably prolonged post-ictal period are characteristic for complex febrile seizures. They may affect otherwise healthy children, but they are also more likely to be triggered by intracranial pathologies than simple FC. Meningitis, for instance, is rarely associated with simple seizures, but incidence rates among patients showing complex FC rise to almost 5% .
There is no consensus about an optimal approach to FC diagnosis. The vast majority of patients present with simple febrile seizures that are merely triggered by common infectious diseases. However, there is a small percentage of FC patients actually suffering from a more severe primary disease. When there is such suspicion, physicians all over the world do extensive workups.
It has to be noted that a thorough anamnesis is the mainstay of FC diagnosis. All diagnostic measures presented hereafter are only indicated if anamnesis and clinical presentation prompt the suspicion of severe illness or intracranial pathologies. This is the case especially for those children that experience complex seizures; possibly also for patients who suffer from repeated simple FC. A first simple febrile seizure in an otherwise healthy patient does not warrant extensive diagnostics .
In general, simple febrile seizures don't require specific treatment. Patients may, however, benefit from antipyretics and possibly additional compounds that relieve symptoms associated with the underlying disease. Long-lasting episodes, i.e., seizures that extend for more than ten minutes, merit anticonvulsants. Distinct benzodiazepines have been successfully applied to pediatric patients suffering from FC. In detail, lorazepam, midazolam, and diazepam are recommended. Fosphenytoin and phenobarbital may also be administered, whereby the latter has a significantly longer half-life.
Long-term therapy is not required. In some cases, prophylactic treatment at the onset of another febrile disease is indicated, since recurrence is likely. Patients aged less than a year upon the first diagnosis of FC, those children that present febrile convulsion within a few hours after onset of low-grade fever, as well as those that already experienced a relapse are most likely to suffer FC again. Nevertheless, FC are rarely observed in pediatric patients aged more than five years.
According to retrospective studies, FC do not interfere with mental or physical development. Retardation has been described in FC patients but has usually been recognized before the first febrile seizure was noted.
However, childhood febrile seizures slightly increase the risk of developing epilepsy later in life. This particularly applies to patients who experience complex FC, i.e., who enter status epilepticus, who show focal seizures rather than generalized ones, or who sustain more than one episode of FC per day.
FC are not associated with mortality unless an adequate treatment is not provided during status epilepticus.
As the name implies, febrile seizures are triggered by increases in body temperature. Young children are particularly susceptible to a wide variety of infectious diseases that provoke fever, e.g., upper respiratory infections, otitis media, and gastroenteritis. In fact, the former has been reported to cause three out of four cases of FC . However, most individuals suffer from such infections during their infancy, but only a minority presents febrile seizures. Thus, additional factors - either predisposing conditions or further triggers - are of major importance in FC etiology. The following have been identified so far :
It is not yet clear how these factors contribute to FC onset. Several genes have been associated with an increased risk of FC, and they are mainly those encoding for cytokines or their receptors. Presumably, disturbances in the development of the immune system and an overall increased risk of infection augment the likelihood of a febrile seizure principally by enhancing the incidence of febrile illness. Risk factors may add up.
Febrile seizures may also be induced by immunization, as has been described for the application of pertussis vaccines (single and combined formulations), measles, mumps and rubella (MMR) vaccines, as well as influenza A (H1N1) vaccines .
The vast majority of FC patients are children aged over one month and less than five years, with highest incidence rates in pediatric patients aged six to twelve months. FC are also the most common type of childhood seizures and it has been estimated that an average of 2 to 5% of all children sustain at least one episode of FC before reaching the age of five. Interestingly, the overall incidence varies largely among distinct geographical regions. In Finland, for instance, 7% of all children presented febrile seizures through the age of four . In Saudi Arabia, in contrast, less than 0.5% of all children are affected . Of note, febrile seizures may rarely be experienced by patients pertaining to other age groups. In adults, FC have been reported as a symptom of an intracranial disease .
Some studies describe a male predominance among FC patients, but other publications refute the hypothesis of gender predilection. Both boys and girls can be affected by febrile seizures. Moreover, no racial predilections have been reported.
The pathophysiologic link between fever and seizures is not yet known. The underlying infection induces an immune response and triggers the release of cytokines, mediators, and other products. These may directly or indirectly (via glial cells) modulate neuronal excitability. Endogenous pyrogens like interleukin-1β and tumor necrosis factor-α are most likely to assume this role. This hypothesis is in agreement with the observation that certain single nucleotide polymorphisms affecting genes encoding for these cytokines are overrepresented in FC patients . To date, it has not been possible though to identify cytokines that may be used as diagnostic markers for febrile seizures.
In few cases, FC may indicate a serious underlying disease like meningitis or encephalitis. An incidence of meningitis in FC patients has been reported to be below 2%, encephalitis is an even less frequent cause of febrile seizures . Streptococcus pneumoniae and herpes simplex virus, respectively, are their most common etiologic agents. Due to the severity of these diseases, the inherent risk should not be underestimated. Similar recommendations shall be given for FC that lead into status epilepticus. Intracranial infections, as well as status epilepticus, are potentially life-threatening conditions.
Because infectious diseases are the direct trigger of fever and febrile seizures, any measure to avoid infection and increases in body temperature may be considered preventive against FC.
Febrile convulsions (FC) are the most common type of seizures in pediatric patients. Although their direct trigger is a pathophysiological increase in body temperature, the precise causes of FC are not yet completely understood. A genetic predisposition has been suggested. The temperature threshold for a pediatric patient to develop FC is presumably lower in some children than in others. In agreement with these hypotheses, FC are frequently observed in children with a family history of FC who contract a febrile infectious disease.
As per definition, FC are not a type of epilepsy, but the likelihood of a child to develop epilepsy later in life after presenting FC is slightly increased when compared to their peers. In general, FC last less than ten minutes and don't imply a disturbance of consciousness or other symptoms that persist for more than an hour. Such seizures are usually generalized and clonic, although tonic spasms have been described. They correspond to what is commonly designated a simple febrile seizure. In contrast, presentation of focal seizures has been proposed as an unfavorable prognostic factor for subsequent epilepsy and is a feature of complex febrile seizures . This also applies to long-lasting convulsions and development of status epilepticus during FC.
Diagnosis mainly aims at ruling out differential diagnoses like Rolandic epilepsy or intracranial lesions, and besides anamnestic data, neuroimaging and electroencephalography are the most helpful tools in achieving this aim. Most children presenting with FC suffer from a viral infectious disease, but other microorganisms may cause fever and trigger the onset of seizures, too. However, it has to be clarified if the child suffers from encephalitis or meningitis. This may require lumbar puncture and analysis of cerebrospinal fluid.
Simple FC may not require specific therapy; standard anticonvulsants like benzodiazepines should be administered in case of prolonged seizures. The outcome is usually excellent and apart from the aforementioned slightly increased risk of epilepsy, sequelae are not to be expected. However, recurrence is likely. This situation normalizes as the child becomes older.
Febrile convulsions (FC) are the most common type of seizures in pediatric patients; they are not considered a form of epilepsy.
Children aged six months to five years are most frequently affected. They are very susceptible to a wide variety of infectious diseases that provoke fever, e.g., upper respiratory infection, otitis media and gastroenteritis. Furthermore, their temperature threshold to sustain FC is significantly lower than in older children.
Upon contracting a febrile infectious disease, pediatric patients may present generalized clonic or tonic seizures that typically don't last any longer than ten minutes. Most patients recover full awareness and freedom of additional symptoms within an hour of FC onset. Simple FC don't imply more than one such episode per day.
In contrast, complex FC present slightly differently. Affected children may show focal seizures rather than generalized ones, enter status epilepticus (i.e., experience uninterrupted seizures for more than 20 minutes), or sustain more than one febrile seizure per day. In rare cases, complex FC may be indicative of severe underlying diseases like meningitis, encephalitis, intracerebral hematoma, cerebral edema or hydrocephalus. Thus, a more extensive workup is required and neuroimaging, as well as electroencephalography, may become necessary.
Of note, children who suffer from complex FC have a slightly increased risk of developing epilepsy at a later point in time.