Myoclonic, tonic, and atonic seizures in children: Clinical and electroencephalographic features

Pharmacology and Therapeutic Aspects of Antiepileptic Drugs in Pediatrics

In the past year, several new antiepileptic drugs have emerged that have potential benefits for children with epilepsy. The spectrum of adverse effects is the principal feature that differentiates among the older drugs used to treat partial and related seizures, including simple partial, complex partial, and partial secondarily generalized seizures. Based on studies in adults with refractory seizures, the new or investigational compounds felbamate, gabapentin, lamotrigine, and vigabatrin should be active against these types of seizures in children, but none of them have been subjected to pediatric randomized controlled trials, and no studies have been done that compare new and old drugs in this category. Thus, the new drugs hold promise in children with these types of seizures, but their role relative to old drugs has not been elucidated. Several of the new drugs are active against myoclonic and generalized tonic-clonic seizures, but thus far, none have been proven to possess antiabsence activity in children. Open-label investigations suggest that lamotrigine may be helpful in Lennox-Gastaut syndrome, and vigabatrin in infantile spasms. Only felbamate has been evaluated in a randomized controlled study in children, in which it has proven beneficial against astatic and generalized tonic-clonic seizures in children with Lennox-Gastaut syndrome. Whereas investigations of these and other novel drugs are ongoing, this is an active and exciting period in pediatric antiepileptic drug development. (J Child Neurol 1994;9(Suppl):2S1-2S7).

Overtreatment in children with epilepsy

Children with epilepsy are at risk for overtreatment, defined as the use of an excessive number or amount of antiepiletic drugs (AEDs). While the extent of overtreatment of epilepsy in children is not known, there is increasing awareness that overtreatment with AEDs contributes to the morbidity associated with childhood epilepsy. Reasons for overtreatment include using AEDs in a child with seizures who does not require therapy, choosing an inappropriate AED for the seizure type or syndrome; treating non-epileptic behaviors as seizures, use of polytherapy when monotherapy would suffice, and inadequate therapeutic options. Despite the introduction of eight new AEDs in the United States during the last decade, many children continue to be treated with the older generation sedative AEDs. Numerous investigators have now demonstrated that sedative AEDs can be safely removed from the drug regimen of children with epilepsy with resultant improvement in behavior, alertness, and improved seizure control. However, the biggest obstacle to overtreatment is the lack of effective therapies for many of the childhood epileptic syndromes. Until there are more effective therapies developed it is highly likely that children will continue to be over-medicated on ineffective and detrimental AEDs.

Lennox-Gastaut syndrome

Lennox-Gastaut syndrome (LGS) is one of the intractable epilepsies of childhood that is associated with an epileptic encephalopathy. Although LGS has been accepted as a distinct epilepsy syndrome for the last 30 years, understanding of its pathogenesis is still incomplete. Because this heterogenous entity has many diverse etiologies, some with specific therapy, a complete evaluation is necessary. The natural history is well defined; most children with LGS will ultimately be mentally retarded, will continue to have seizures, and as adults will be dependent for their daily care. Therefore, their only hope is new therapies and advances in our understanding of the pathogenesis of LGS. Several new treatment options have emerged. For the first time in the last 20 years, we have several medications with documented efficacy. In addition, there are effective nonpharmacologic treatments. These treatments offer the potential for improved seizure control, which we hope will have impact and lessen the subsequent epileptic encephalopathy. Children with LGS require multidisciplinary assessment and treatment along with vigorous intervention aimed at minimizing their seizures to maximize their potential. Pediatric neurologists should be familiar with the treatments with proven efficacy, including new antiepileptic drugs, and should develop a rational plan of treatment for each child with LGS.

The age-dependent epileptic encephalopathies

The most severe epilepsies that affect neonates, infants, and children include Ohtahara, West, and Lennox-Gastaut syndromes. These three syndromes display considerable similarities and transitional features in their clinical symptoms, seizure phenomena, and electroencephalographic abnormalities. This review examines the similarities and differences between these three syndromes and the other severe epilepsies of infancy and childhood, and discusses the hypothesis that the three disorders form a continuum of epileptic encephalopathies that have a predictable age-related evolution.