Practical management issues for idiopathic generalized epilepsies.

Abstract

The idiopathic generalized epilepsies (IGE) are a group of epilepsies that are genetically determined, have no structural or anatomic cause, and usually begin early in life. Neurologic examination, intelligence, and imaging studies are normal, and EEG shows only epileptiform abnormalities (i.e., no abnormal slow activity or evidence for diffuse encephalopathy). In some IGE, the genetic substrate has been identified, whereas in most, it remains unknown. Depending on the age at onset and predominant seizure type, individual subtypes of IGE (syndromes) are defined. However, overall, there are more similarities than there are differences among the various subtypes, and the IGE are best viewed as a spectrum or continuum of conditions. In general, IGE respond to treatment, with 80-90% becoming fully controlled. However, not all antiepileptic drugs (AED) are equally effective in IGE. Some AED are ill advised because they either do not work or exacerbate seizure types other than generalized tonic-clonic (GTC) seizures, that is, absence and myoclonic seizures. These include carbamazepine, oxcarbazepine, phenytoin, gabapentin, and tiagabine. Their use is the main cause of "pseudo-intractability," and at least in the United States where PHT and CBZ are the most commonly used AEDs, patients with IGE are often on inadequate medications. For patients with clear IGE, the drug of choice is generally valproic acid because it effectively controls absence myoclonic seizures and GTC seizures. Second-line drugs (when first-line drugs fail or are not tolerated) may include benzodiazepines, but the use of second-line drugs is evolving rapidly. Some of the newer AEDs are considered broad spectrum, meaning that they work in IGE and focal epilepsies, although the evidence is largely preliminary at this point. These newer AEDs include lamotrigine, topiramate, levetiracetam, and zonisamide.