Children between the ages of 3 months and 5 years have a lower seizure threshold and are susceptible to febrile seizures. Up to 5% of children in the U.S. experience a febrile seizure by their fifth birthday. A simple febrile seizure does not require workup with special blood tests, imaging studies, lumbar puncture (unless other signs and symptoms of meningitis are present), or an electroencephalogram (EEG). Children who experience a complex febrile seizure and have a family history of epilepsy or developmental delay appear to have a higher risk of developing afebrile seizures. Recurrent febrile seizures are more likely in patients who had their first febrile seizure at a young age, a relatively low fever at time of presentation with first seizure, a history of febrile seizures in a first-degree relative, or a brief duration between fever onset and initial seizure. An initial simple febrile seizure does not require treatment (except perhaps antipyretics and treatment of the source of the fever), while other types of febrile seizures require weighing the risk of further seizures against the risk of side effects from anticonvulsants.
Table 7. General classification of seizure type
Partial seizures secondarily generalized
Absence Tonic/Clonic Myoclonic Atonic
Simple febrile seizures, which are generalized and last less than 15 minutes, should be distinguished from complex events, which are prolonged, occur more than once in 24 hours, or are focal. Although an abnormally high proportion of adults with temporal lobe epilepsy have a history of febrile seizures, it is not clear whether subtle structural abnormailities in these patients produced a lower seizure threshold during childhood, or whether the febrile seizures were responsible for the development of the seizure foci.
Seizures are classified according to the scheme of the International League Against Epilepsy (ILAE, Table 7). Symptomatological, electrophysiological and imaging findings are needed to accurately classify epileptic events. Classification of seizure type should not be confused with identification of a seizure focus, although these two exercises overlap to some degree. Determination of the seizure focus is requisite before deciding upon definitive therapies. The identification of a seizure focus also requires detailed knowledge of the symptoms, electrophysiological findings, and the results of imaging studies. In the current era, this often includes computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT).
Partial seizures are those that arise from a focal region of the cortex. They are simple partial seizures if the discharges elicit disturbance of sensory or motor symptoms without causing an alteration in consciousness. The symptoms that accompany a seizure provide clues about the location of the focus. Children with simple partial seizures in whom no lesion is identified are often not appropriate candidates for resective surgery. Benign Epilepsy of Childhood with Rolandic Spikes, also called Benign Rolandic Epilepsy, is an entity seen among children from 0 to 15 years old. This entity is important to recognize as it responds well to pharmacological therapies and seizures recede in all patients by age 15.
Complex Partial Seizures
Complex partial seizures are those that produce some alteration of consciousness, such as visual or auditory hallucinations, a sense of deja vu, or some impairment of contact with the outside world. The most frequent cause of such seizures is mesial temporal sclerosis.
Generalized seizures arise diffusely from the cerebral cortex. For making therapeutic decisions, it is critical to distinguish between primary generalized seizures, and focal seizures with secondary generalization. In the latter case, removal or disconnection of an isolated focus may prevent generalization.
Pharmacological therapy depends very much on the classification of seizure type. Seizure type may predict both the likelihood of improvement and the risk of clinical deterioration in response to a given anticonvulsant. (An outline of the individual agents, their mechanism of action, common dosages, common therapeutic levels, oral absorption, metabolism, selected common side effects and selected interactions with other anti-epileptic drugs is given in Table 8.) The general principles of phar-macotherapy are to begin with a single agent (monotherapy), increase the dose to the maximum tolerable if seizures are refractory, and when maximized on monotherapy, begin to add-on. Follow the maxim "start low, go slow." Certain seizure types respond to specific medications (Table 9).
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