A febrile seizure is a seizure disorder that occurs in children between 6 months and 5 years of age, in association with a fever but without evidence of intracranial infection. The first febrile seizure in the majority of children occurs before 3 years, with the average age at onset between 18 and 22 months. Most studies have demonstrated a higher incidence in boys.

Febrile seizures may be of any type, although they are usually generalized tonic-clonic or tonic. Febrile seizures are classified as complex if the seizure duration is longer than 15 minutes, if more than one seizure occurs in 24 hours, or if focal features are present.

Electroencephalography (EEG) has not been found to be useful in the evaluation of a child with febrile seizures. Although some controversy remains, most authorities believe that the EEG is a poor predictor of either febrile or afebrile seizure recurrence. Approximately one third of patients with febrile seizures have an abnormal EEG when the record is obtained within a week of the seizure. The most common abnormality is occipital slowing, but generalized spike-and-wave and focal spikes may occur. However, this epileptiform activity is not predictive of the eventual development of epilepsy. The American Academy of Pediatrics does not recommend the use of routine EEG in patients with febrile seizures.

The physician must first identify whether an underlying illness exists that requires immediate, specific treatment. The most urgent diagnostic decision is whether to do a lumbar puncture. One of the earliest signs of meningitis may be a seizure that, like a febrile seizure, is usually short and generalized tonic-clonic. (Although meningitis typically results in meningismus, in patients younger than 2 years, clinical signs of meningitis may be minimal or absent.)

In the absence of specific clinical indications, the literature yields little evidence indicating that other tests are helpful in determining etiology of seizures associated with fever. Skull films,
serum glucose, calcium, blood urea nitrogen, and electrolytes are of low yield and are not routinely recommended. Brief, single, self-limited febrile seizures from which the child fully recovers are seldom caused by conditions such as hypoglycemia or toxins. Unless the physical examination points to a possible structural lesion, a computed tomographic scan or magnetic resonance imaging is not warranted in the evaluation of febrile seizures. Because the EEG is of questionable value after febrile seizures, routine EEGs are not necessary.

Most experts agree that no preventive therapy is indicated for the child who has experienced a first or even a second febrile seizure. In practice parameters provided by the American Academy of Pediatrics, it is stated that the potential adverse effects of prophylactic therapy are not commensurate with the benefit. Children who experience complex febrile seizures, characterized by partial or prolonged seizures and concomitant neurologic developmental abnormality, are more likely to have recurrent seizures. These patients are frequently considered to have epilepsy initially triggered by fever and are more often treated with long-term antiepileptic drug therapy.

For children who experience frequent or prolonged febrile seizures, treatment with oral diazepam (0.3 mg/kg every 8 hours) during the febrile illness will reduce the likelihood of a seizure. However, parents may not be aware that the child has a fever until a seizure occurs. In addition, diazepam can lead to significant lethargy and possibly mask signs of a serious illness such as meningitis. Most physicians no longer use oral diazepam as prophylactic therapy, Diazepam rectal gel (Diastat) can be administered at the onset of a febrile seizure in a child with a history of prolonged seizures. See Chapter 11 for dosage recommendations.

Febrile seizures are associated with a very low mortality rate. When deaths do occur, they are almost always secondary to the agent causing the fever or to an antecedent neurologic disorder. In addition, the incidence of acquired motor or intellectual abnormalities after a febrile seizure is low.

Although relatively few children who experience febrile seizures develop epilepsy, recurrences of febrile seizures are
commonplace. In the National Collaborative Perinatal Project, approximately one third of the children had at least one recurrence, and one half of those who had one recurrence had an additional attack.

Recurrence risk is not uniform for all children with febrile seizures. The most important factor appears to be age at onset of the first febrile seizure. The younger the child at the first attack, the more likely are further febrile seizures. Children who experience their first seizure at younger than 13 months have a greater than a 2:1 chance of developing further febrile seizures. This compares with a risk of approximately 20% in patients who have their first febrile seizure after age 32 months. Three fourths of recurrence takes place within 1 year of the first febrile seizure, and 90% within 2 years.

Although children who have one or more febrile seizures are at higher risk than the normal population for the development of epilepsy, the risk is quite small. A large epidemiologic study in the United States examined the frequency of afebrile seizures in 1,706 children who had experienced at least one febrile seizure and were followed up to the age of 7 years. At least one afebrile seizure had occurred by the age of 7 in 3% of the patients with febrile seizures. Two percent of the group had two or more afebrile seizures by age 7 and would be considered to have epilepsy. Of 39,179 children who had never been reported to experience a febrile seizure, 0.5% had epilepsy by age 7 years. The risk for developing epilepsy, therefore, was 4 times higher in the group that had febrile seizures.

The risk of developing unprovoked seizures is increased by several factors: neurodevelopmental anomalies, complex febrile seizures, recurrent febrile seizures, brief duration of fever before initial seizure, and family history of epilepsy.

Prolonged febrile seizures have been implicated as a predisposing factor for the development of temporal lobe epilepsy and mesial temporal sclerosis, a pathologic condition of hippocampal sclerosis and atrophy with loss of neurons in the CA1 region and the end-folium region (CA3/CA4), but with relative sparing of the CA2 region (see Chapter 3). In most children with prolonged febrile seizures, temporal lobe epilepsy does not develop. Whether febrile status epilepticus plays a causal role in mesial temporal sclerosis is not clear but is now undergoing study.

A large epidemiologic study found that children who had febrile convulsions (simple or complex) performed as well as other children in terms of their academic progress, intellect, and behavior at 10 years.

This syndrome (GEFS+) most often manifests with childhood onset (median age, 1 year) of multiple febrile seizures. Unlike typical febrile seizures, seizures with fever may persist beyond years 1 through 5, and afebrile seizure may also occur. Seizures usually cease by mid-childhood (median age, 11 years). Other phenotypes may include absence, myoclonic, atonic, or myoclonic-astatic seizures (see ref. 23 for details). This seizure type is inherited in an autosomal-dominant pattern with 50% to 60% penetrance and has been linked to multiple loci including: 2q24 (SCN1A and
SCN2A), 19q13 (SCN1B), and 5q31 (GABRG2). The genes on 2q24 and 19q13 produce subunits of the voltage-gated sodium channels, whereas the gene on 5q31 codes for the γ₂ subunit of the γ-aminobutyric acid (GABA)_A receptor. The sodium channel is composed of an α subunit and one or more regulatory β subunits, and mutations of the subunits typically result in an increase in Na⁺ currents and an increase in excitability. Phenotypes also vary across families because of different mutations and differences in other genetic and environmental cofactors.

As example of the varying phenotype associated with the sodium channel mutations is severe mycolonic epilepsy of infancy (SMEI), also called Dravet, a devastating disorder characterized by severe myoclonic seizures and mental regression. Mutations in SCN1A have been found in SMEI (Dravet syndrome), and most mutations are spontaneous. In 30% to 70% of SMEI patients, truncating and missense mutations in (SCN1A) have been identified. The majority of patients have truncating mutations that are predicted to be loss-of-function alleles. Recent evidence suggests that the Na⁺ channels with mutations are expressed preferentially on interneurons. The loss of function of Na⁺ channels in interneurons would be expected to lead to a severe lack of effective inhibition in the children and may account for the severe seizure phenotype. In addition to Dravet syndrome, some infants with other forms of early childhood epilepsy have SCN1A mutations (10).

Patients usually are chronic alcoholics 30 years of age or older (Table 8-2). Ninety percent of alcohol-withdrawal seizures occur 7 to 48 hours after cessation of drinking, and 50% occur 13 to 24 hours after drinking has ceased. Thus some alcohol often is still present in the plasma at the time of the seizure, and the patient’s breath may have the odor of alcohol on arrival at the hospital. Alcohol-withdrawal seizures can occur up to 7 days after stopping drinking. Clinical examination frequently reveals tremulousness and some myoclonic jerks of the extremities. Seizures typically are generalized-onset tonic-clonic. Seizures may be single (40%) or multiple (usually two to four). The time between the first and last seizure usually is less than 6 hours. If untreated, in one third of patients, full-blown delirium tremens develops, and in a small number, tonic-clonic status epilepticus.

The interictal EEG of the patient with alcohol-withdrawal seizures usually is normal, and the ictal EEG shows the typical findings of tonic-clonic seizures. In 50% of untreated patients, heightened excitability to photic stimulation (photoconvulsive or photomyoclonic responses) is present for 12 to 130 hours after cessation of drinking. This can be a clue to surreptitious alcoholism in a patient with a first tonic-clonic seizure. Photic excitability usually disappears immediately after treatment with a benzodiazepine.

Ethanol does not appear to have a specific ethanol receptor in the brain. Rather, ethanol modulates the action of three ligand-gated ion channels; ethanol facilitates the action of GABA on chloride channels. This results in facilitation and downregulation of GABA-mediated inhibition. Ethanol inhibits the action of glutamate on N

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