Aspects of Antiepileptic Treatment in Children

Summary: About 75% of patients with epilepsy have seizures during childhood, often requiring antiepileptic therapy. Children possess all the drug-specific pharmacokinetic features of adults (e.g., nonlinearity of phenytoin elimination and autoin-duction of carbamazepine metabolism), plus other factors (e.g., age, intercurrent illness, comedication) that influence dosage. Kinetic differences are maximal in newborns and infants, with limited drug elimination in premature and full-term babies, soon followed by accelerated elimination during infancy and childhood, before lower adult elimination rates develop during late childhood or early adolescence. Most children with epilepsy require two- to fourfold larger doses relative to bodyweight than adults, to achieve comparable drug levels and therapeutic effects. Although rapid growth may require increased dosage, the need is limited as relative clearance declines with age. Children of any age, but particularly premature and newborn babies, show greater individual variability in drug handling and therefore in dose requirements than adults. Clinical response and antiepileptic drug concentrations should both be monitored carefully in children.     

Antiepileptic Drug Utilization in Pediatric Patients

Summary: Children require larger relative doses of antiepileptic drugs than adults, and because of the greater patient-to-patient variability among children, an “average” dose is less likely to be correct for a given child. Newborns with convulsions initially have very slow drug elimination; as a group, they also have the widest range of pharmacokinetic values. After the first week of life, drug eliminating mechanisms mature and drug dosage requirements often increase dramatically. Thus in the first 6 weeks of life, intrapatient variation is a significant problem and frequent dosage changes are usually required. Thereafter a given child's kinetics are fairly stable. Infants 2 to 12 months old have the highest rates of drug clearance and often require relative doses that are 3 to 5 times larger than doses for adults. After infancy, relative dosage requirements progressively decline until adult values are reached by 10 to 15 years of age. Newborns, infants, and children, as well as adults, have nonlinear kinetics for phenytoin. Thus a wide range of apparent half-lives occur in children, depending on the phenytoin concentration and other factors. Because the kinetics of antiepileptic drugs are so highly variable in children, antiepileptic drug concentration measurements are an essential aspect of the contemporary treatment of children with epilepsy.     

Are febrile seizures an indication for intermittent benzodiazepine treatment,and if so,in which cases?

Febrile seizures occur in ～4% of children. After a first febrile seizure, the risk of recurrence is ～40%, but excellent studies document that febrile seizures do not cause brain damage or deficits in cognition or behaviour. The risk of subsequent epilepsy is 2–4%. Prolonged febrile seizures are of concern because a child may later develop mesial temporal sclerosis and intractable epilepsy in rare cases. Most prolonged febrile seizures represent the first febrile seizure and cannot be anticipated. A first prolonged febrile seizure does not increase the risk of recurrence, but if there is a recurrence, it is more likely to be prolonged. Prevention of recurrent febrile seizures is difficult. Antipyretics are ineffective. Daily AED treatment is not often justified. Intermittent oral diazepam at the time of illness is not very successful and has significant side effects. The most optimistic study found that the number of subjects required to treat in order to prevent one recurrence was 14. Intermittent clobazam has fewer side effects than diazepam and may be somewhat effective. Rescue benzodiazepines given outside health care facilities may be effective in selected patients to prevent prolonged recurrences, although this has not been proven with rectal diazepam which has been more extensively studied than buccal or nasal midazolam. Currently, we suggest that, for children with febrile seizures, candidates for consideration for rescue benzodiazepines are those with a prolonged febrile seizure or poor access to medical care. It is possible that the use of a rescue benzodiazepine may alleviate severe parental anxiety, but this remains to be established.     

Intermittent prophylaxis in febrile convulsions with oral diazepam]

Intermittent prophylaxis with oral diazepam is presented as an optional treatment for febrile seizures. This proposition is justified by the severe side effects of the currently used chronic anticonvulsant drug therapy in febrile seizures (phenobarbital and valproate). Nineteen patients aged between 3 months and 5 years were treated. They had either simple or complex febrile seizures. Sixteen patients had at least one prognostic factor for recurrence of febrile seizures: first febrile seizure before 15 months of age, positive family history for epilepsy or febrile seizures, occurrence of a complex febrile seizure or abnormal neurological examination. Three patients had none (cases 8, 12 and 13). We recommended 2.5mg b.i.d. for children younger than 12 months, 5mg b.i.d. for children older than 12 months and younger than 3 years, and 7.5 b.i.d. for children older than 3 years. The results showed that only one patient had febrile convulsions while taking adequate diazepam dosage. Transient side effects occurred in 36.8% of the cases.     

Febrile seizures: treatment and prognosis

Recent epidemiologic data indicate that the vast majority of children with febrile seizures have a normal longterm outcome. A precise knowledge of the short- and long-term outcome with or without treatment, and short- and long-term side effects is an important prerequisite for assessing the various treatment strategies. We focus on the impact of short-term or prophylactic treatment on the short- and long-term outcome of various types of febrile seizures. There is universal agreement that daily prophylaxis with antiepileptic agents should never be used routinely in simple febrile seizures, but only in highly selected cases, if at all. Intermittent diazepam (DZP) prophylaxis at times of fever may or may not reduce the recurrence rate, but it does not appear to improve the long-term outcome as compared with short-term seizure control. The treatment may be used to reduce the recurrence rate for a small arbitrarily defined group with multiple simple febrile seizures, complex febrile seizures, especially focal, prolonged or both, febrile status, and when parental anxiety is severe. However, there is no evidence that treatment of simple febrile seizures can prevent the rare cases of later epilepsy, and many children with complex febrile seizures have a benign long-term outcome, even without treatment. Many prefer a "wait and see" policy. An attractive alternative is to treat new febrile seizures with rectal DZP in solution at seizure onset, given by the parents at home to prevent febrile status. Newer, less well documented short-term strategies include nasal, oral, or rectal administration of other benzodiazepines. Short-term seizure control of febrile status and careful parental counseling are the two most important targets of treatment.     

Nonfebrile Illness Seizures: A Unique Seizure Category?

PURPOSE: To describe the clinical characteristics of children with a first-time nonfebrile seizure in the setting of mild illness and to test the hypothesis that these seizures are associated with illness characterized by diarrhea. METHODS: This retrospective cohort study was performed in a pediatric emergency department. Patients ages 6 months to 6 years who were evaluated with first-time seizures were eligible for inclusion. Subjects were divided into three groups on the basis of symptoms accompanying their seizure: febrile (temperature, >38.0 degrees C with seizure), unprovoked (no symptoms of illness), and nonfebrile illness (no fever at the time of seizure, but other symptoms of illness present). RESULTS: Of the 323 children with first-time seizures, 247 (76%) had febrile seizure, 37 (12%) had unprovoked seizures, and 39 (12%) had nonfebrile illness seizures. Children with nonfebrile illness seizures were more likely than children with febrile seizures to have diarrheal illnesses accompanying their seizure (44 vs. 16%; p=0.001). Frequency of cough, rhinorrhea, and rash did not differ significantly between children with febrile and nonfebrile illness seizures. Diagnostic testing for infectious etiologies was not performed frequently in either group. CONCLUSIONS: Nonfebrile illness seizures may represent a distinct group of seizures with unique epidemiology. Further study to define this seizure group better is warranted.     

Childhood-onset epilepsy with and without preceding febrile seizures

OBJECTIVE: To identify characteristics in children with epilepsy that differ between those who did versus did not have a history of preceding febrile seizures. BACKGROUND: Febrile seizures precede epilepsy in 10 to 15% of children. Little is known about the specific types of epilepsy associated with febrile seizures. METHODS: In a community-based, prospectively identified cohort of children, the association between prior febrile seizures and characteristics of the children's epilepsy (seizure type, epilepsy syndrome, age at onset, underlying etiology, family history) were examined for 524 of the children who were aged > or =1 year at onset of epilepsy. RESULTS: Seventy-three (13.9%) had febrile seizures. Children with febrile seizures were more likely to have a first-degree or a second-higher-degree relative with febrile seizures and less likely to have childhood absence epilepsy and absence seizures compared with children without febrile seizures. This was especially true for simple febrile seizures. There was no specific association with localization-related forms of epilepsy. Complex, but not simple, febrile seizures were associated with younger age at onset of epilepsy. There was no evidence that focal or prolonged febrile seizures were associated with localization-related epilepsy or temporal lobe epilepsy per se. Of the three children whose initial MRIs demonstrated hippocampal atrophy, none had a history of febrile seizures. CONCLUSIONS: At the time of diagnosis, febrile seizures are not specifically related to temporal lobe epilepsy or localization-related epilepsy in general. A genetic component for febrile seizures is suggested by its positive associations with family history, especially for simple febrile seizures. Complex febrile seizures represent an underlying age-dependent susceptibility.     

INFANTILE FEBRILE STATUS EPILEPTICUS: RISK FACTORS AND OUTCOME

The medical records of 68 children who had had infantile febrile status epilepticus (FSE) were examined. Follow-up periods ranged from three to 28 years (mean 8 years 10 months). Details were abstracted of relevant medical events prior to FSE, diagnosis of the febrile illness, age at onset and main characteristics of FSE, and outcome (subsequent febrile convulsions and/or epilepsy, neurological and psychiatric disorders). Neither medical events prior to FSE nor aetiology of fever were associated with subsequent febrile convulsions, epilepsy, or neurological or psychiatric abnormalities. There was a significant association between age at onset of FSE and both subsequent epilepsy and CNS disorders. 12 of the 13 children who had had transient or persistent post-ictal hemiparesis subsequently developed epilepsy. Of the 46 children who later developed epilepsy, 34 had partial seizures and 12 had generalized seizures. The latter were more common among children who had had FSE before the age of one year. Likewise, all those who developed severe myoclonic epilepsy in infancy had their first FSE before age one. These findings suggest that age at onset of FSE is the most important feature determining long-term outcome.     

Risk Factors for a First Febrile Seizure: A Matched Case-Control Study

Summary We conducted a matched casecontrol study to identify risk factors for first febrile seizures, with special emphasis on characteristics of the acute illness episode. Cases were identified through hospital emergency departments; controls were identified through outpatient clinics and emergency departments. Sixtynine children with first febrile seizures and no history of previous unprovoked seizures were matched for age (±6 months), site of routine pediatric care, and date of visit (±weeks) with 1 or 2 febrile controls who had no history of previous febrile or unprovoked seizures. Medical records for the index visit were reviewed, and parents were interviewed by telephone. Illness characteristics examined included height of temperature, type of underlying illness, contact with a physician during the illness but before the index visit, and use of acetaminophen or decongestants. Family history of febrile and of unprovoked seizures, sociodemographic characteristics, daycare use, and selected preand perinatal variables were also studied. On multivariable analysis, significant independent risk factors were height of temperature, history of febrile seizures in a firstor in a higher degree relative. Gastroenteritis as the underlying illness had a significant inverse (i.e., protective) association with febrile seizures. Maternal smoking during pregnancy was a marginally significant predictor of febrile seizures.     

Efficacy of a diazepam suppository at preventing febrile seizure recurrence during a single febrile illness

Purpose: To assess the efficacy of diazepam suppositories at preventing febrile seizure recurrence during a single febrile illness to determine how to treat children with a febrile seizure on presentation at the hospital. Methods: We studied 203 children with febrile seizures from December 2004 through March 2006. On admission between December 2004 and May 2005, a diazepam suppository was administered to the patients. Patients seen between June 2005 and March 2006 were not treated with antiepileptic drugs on admission. Results: We saw a significant difference in the rate of recurrence of febrile seizures between children treated with diazepam and those who were not. Recurrences were observed in 2 (2.1%) of 95 children treated with diazepam and in 16 (14.8%) of 108 untreated children. For the 108 untreated patients, the median age was 22.8 months in those with recurrences and 30.6 months in those without, confirming that a younger age was related to a recurrence. Conclusions: A diazepam suppository after a febrile seizure will reduce the incidence of recurrent febrile seizures during the same febrile illness. However, a diazepam suppository after a febrile seizure should be used after carefully considering the benefits and potential adverse effects.     

Valproic acid pharmacokinetics in children: III. Very high dosage requirements

Nine children were studied who required very high doses of valproic acid (VPA) (63.6-105 mg/kg/day) in order to achieve VPA serum concentrations between 50-100 micrograms/ml. These nine children had poorly controlled seizures and were receiving other antiepileptic drugs at the time of this study. The children with very high dose requirements were significantly lighter, shorter, and had less body surface area than the control group. Of the pharmacokinetic parameters studied, total and intrinsic clearance, distribution volume, and valproic acid free fraction were significantly increased in the very high dose group. In three patients who were investigated after co-medications were eliminated, clearances and dosage requirements decreased by more than 50%. We concluded that very high VPA dosages are sometimes required to achieve therapeutic serum drug concentrations and that this therapy occasionally improves seizure control. There were no adverse effects of very high dose therapy that required dosage reduction.     

Carbamazepine Efficacy and Utilization in Children

Summary: Carbamazepine is effective for preventing partial and generalized tonic-clonic seizures in children. Although absence epilepsies are more common in children than adults, an estimated 80% of children with epilepsy have seizure types or epilepsies that are potentially responsive to carbamazepine. The differential diagnosis of ictal staring is an especially important issue in children because absence and atypical absence seizures are more prevalent in children than adults. Age-related pharmacokinetic differences and drug interactions are major considerations in children. On average, children have higher clearance rates of carbamazepine, shorter half-lives, and higher ratios of carbamazepine-10, 11-epoxide to carbamazepine than adults. In addition, children with severe epilepsy are more likely to require multiple-drug therapy, which can lead to complex drug interactions. When carbamazepine is administered along with valproate, drug protein binding interactions can cause intermittent side effects.     

Short-term outcomes of children with febrile status epilepticus

Febrile status epilepticus (SE) represents the extreme end of the complex febrile seizure spectrum. If there are significant sequelae to febrile seizures, they should be more common in this group. We have prospectively identified 180 children aged 1 month to 10 years who presented with febrile SE over a 10-year period in Bronx, New York, and Richmond, Virginia. They were compared with 244 children who presented with their first febrile seizure (not SE) in a prospective study done in the Bronx. The mean age of the children with febrile SE was 1.92 years, and of the comparison group, 1.85 years. Duration of SE was 30-59 min in 103 (58%), 60-119 min in 43 (24%), and > or =120 min in 34 (18%). Focal features were present in 64 (35%) of cases. There were no deaths and no cases of new cognitive or motor handicap. Children with febrile SE were more likely to be neurologically abnormal (20% vs. 5%; p < 0.001), to have a history of neonatal seizures (3% vs. 0; p = 0.006) and a family history of epilepsy (11% vs. 5%; p = 0.05) and less likely to have a family history of febrile seizures (15% vs. 27%; p = 0.01) than were children in the comparison group. The short-term morbidity and mortality of febrile SE are low. There are differences in the types of children who have febrile SE compared with those who experience briefer febrile seizures. Long-term follow-up of this cohort may provide insight into the relationship of prolonged febrile seizures and subsequent mesial temporal sclerosis.     

Which factors determine febrile seizure recurrence? A prospective study

PURPOSE: Many factors have been studied as potential predictors of recurrent febrile seizures (FS), however the available data in literature are inconsistent. The aim of the present paper is to determine which factors are responsible for the first and for multiple recurrences of FS, in a large sample of children with a long-term follow up. METHODS: Two hundred and sixty children were followed after their first FS. The inclusion criteria were: a history of a first febrile seizure; no personal history of afebrile seizures; no previous anticonvulsant medication and age between three months and six years. The median time of follow up was 4.3 years. We had a contact with the families of the children every 4-6 months and also in every recurrence. RESULTS: Very significant prognostic markers for the first FS recurrence were low age at onset, recurrence within the same illness, frequent febrile episodes and maternal preponderance. Powerful prognostic factors that may predispose children who already have one recurrence to a second or more are low age at onset and especially positive family history of FS. Additionally, low temperature prior to the initial seizure is a powerful predictor for three or more recurrences. CONCLUSIONS: Prognostic factors for FS recurrence are a useful tool for the clinician. It is obvious that as many powerful predictors a child has, the greater will be the risk for FS recurrence.     

Clinical implications of benzodiazepine pharmacokinetics.

Pharmacokinetic research has shown that clear differences exist among benzodiazepines in rate and route of elimination and in the presence or absence of pharmacologically active metabolites. These findings and other results of pharmacokinetic research have clinical implications in terms of dosage schedules, drug accumulation during long-term therapy, antianxiety therapy in the elderly, drug interactions, pharmacotherapy in specific disease states, and the influence of route of administration on drug action.     

Febrile Seizures: Clinical Characteristics and Initial EEG

We examined the relationship between clinical characteristics and EEG classification in all children with febrile seizures examined at the University Pediatric Clinic, Skopje, Yugoslavia between 1982 and 1984. This is the only facility in Macedonia providing EEG or neurologic consultation for children. EEGs were classified as paroxysmally abnormal if they contained spikes, sharp waves, or spike-wave complexes considered abnormal for age. In all, 22% of the 676 children had an abnormal initial EEG. The most common basis for classification as abnormal was spike-wave complexes greater than 3 Hz; the next most common basis was the presence of spikes. Birth weight, gender, accompanying illness, and family history of seizures, and whether the index seizure was single or multiple were not associated with differences in rate of abnormal EEG. Clinically focal index seizures and longer duration were associated with EEG abnormality. Number of previous febrile seizures was associated with an increasing rate of EEG abnormality, from 18% in children with no previous seizures to 63% in those with four or more previous seizures. Age at EEG was linearly related to likelihood of paroxysmal EEG abnormality, both for the total cohort and for the 376 children with no previous seizures. In the total cohort, logistic regression identified leading predictors of abnormal initial EEG to be older age, number of previous febrile seizures, preexisting motor abnormality, and focal seizures. For children with a first febrile seizure, leading predictors were focal seizure, older age, and preexisting motor abnormality.     

The risk of epilepsy following febrile convulsions

A cohort of 666 children who had convulsions with fever were followed to determine the risks of subsequent epilepsy. High risks were found in children with preexisting cerebral palsy or mental retardation. Other major risk factors were atypical features of the febrile convulsions (such as focal seizures) and duration of febrile seizures for 10 minuts or more. The risk of developing epilepsy by age 20 was about 6 percent for all children who had experienced febrile convulsions. However, this risk figure consisted of a combination of 2.5 percent of children without prior neurologic disorder or atypical or prolonged seizures, and 17 percent of those with such complications.     

Exogenous causes of seizures in children: A population study

Of many exogenous causes, difficult birth, neonatal asphyxia, and coiling of the umbilical cord might be identified as risk factors predicting an initial febrile convulsion. Children with febrile convulsions and exogenous causes are likely to have affected family members, and have a risk of recurrence of seizures on 5 occasions or more. Exogenous causes alone barely raise the risk of recurrence of febrile convulsions after 3 years of age or development of afebrile convulsions. The incidence of exogenous causes is highest in children who develop afebrile convulsions after febrile convulsions, and lowest in children who experience only febrile convulsions, although a little higher than in normal controls.     

Influenza A and febrile seizures in childhood

The aims of the present study are to identify predisposing factors of febrile seizures in influenza A infection and to clarify the special characteristics of febrile seizures in children with influenza A infection. Between January and July 2005, children hospitalized because of febrile seizures and subsequently confirmed influenza A infection were enrolled as subjects. Age-matched control subjects were those admitted as a result of influenza A infection but no febrile seizures (control 1) and children who developed febrile seizures with negative viral studies (control 2). Significant factors for the development of febrile seizures include: history of febrile seizures, family history of seizure disorders, and coexisting gastroenteritis. Independent risk factor for febrile seizures was history of febrile seizures (odds ratio 7.58, 95% confidence interval CI 1.48 to 38.84, P = 0.015). When compared with children who developed febrile seizures with negative virus studies, children who developed febrile seizures in influenza A infection had a significantly higher maximum body temperature, shorter duration of fever before seizure onset, and more frequent occurrence of partial seizures. Current episode represented first seizure in 26.5% of children infected with influenza A as compared with 50% of children whose virus studies were negative (P = 0.04). The findings suggest that effective vaccination may prevent development of febrile seizures, especially in those patients with past history of febrile seizures. Rapid diagnostic testing for influenza infection in the management of complex febrile seizures, especially during influenza season, is cost-effective.     

Discontinuing Medication in Epileptic Children: A Study of Risk Factors Related to Recurrence

We studied 70 children who had experienced at least two seizures before age 12 years, excluding febrile seizures, neonatal seizures, or seizures occurring during a metabolic, or infectious insult to the central nervous system (CNS) and who had been seizure free for at least 2 years. Twenty children (28.5%) experienced a recurrence, 75% during antiepileptic (AED) drug discontinuation or less than 6 months after discontinuation. Risk factors statistically related to seizure recurrence were greater than 10 seizures before seizure control, an abnormal EEG in the year before AED discontinuation, presence of focal neurologic signs and/or mental retardation, and presence of a mixed seizure pattern. Fourteen children (70%) with recurrence had two or more risk factors, whereas 36 (72%) without recurrence had no risk factor or only one. We conclude that a selected group of epileptic children who remain seizure-free for a period of at least 2 years can have AEDs discontinued based on presence or absence of risk factors.