When Do Epileptic Seizures Really Begin?

Previews filtered voltage (see figure). A channel recording low-Seizures Really Begin? severe and widespread damage to the cerebral cortex would typically have low signal energy, while a high-voltage, wildly varying signal recorded from an individual during a seizure would represent high signal energy. Epilepsy, a disorder characterized by recurrent seizures, How the energy accumulates over time can be easily is a common neurological problem, affecting more than calculated so that the overall energy pattern over min-two million Americans and 1% of the population world-utes to hours can be visualized (see figure, " accumu-wide. Epileptic seizures occur with little or no warning, lated energy ") as opposed to the fine detail second-to-commonly impair awareness, limit an individual's ability second changes. to operate a motor vehicle or function effectively in the Two findings of particular interest emerged from this workplace, and render the victim susceptible to bodily work. The first was that computation of signal energy harm. No effective prevention is available. Drug therapy during the entire recording period disclosed fleeting into suppress seizures is unsatisfactory; at least 25% of creases evident hours in advance of seizure onset (Fig-affected individuals experience persistent seizures de-ure 2 of Litt et al., 2001). Also termed " bursts " by the spite optimal treatment. If an impending seizure could authors, these fleeting increases of signal energy lasted be predicted tens of minutes in advance, a diversity of at least 5 min and their occurrence increased in fre-novel therapeutic options would emerge. The work of quency during the several hours prior to seizure onset Litt et al. (2001), in this issue of Neuron, represents (Figure 4 of Litt et al., 2001). Importantly, these increases an initial effort to predict the occurrence of epileptic of signal energy were not associated with any overt seizures tens of minutes in advance by computerized change in behavior of the patient. The quantitative analy-analysis of the electroencephalogram (EEG). ses of signal energy were restricted to three of five The EEG has been and remains the single most impor-individuals in the study in which the " earliest EEG tant diagnostic test for epilepsy. One example of its changes " were highly localized. In two of these three usefulness lies in studies of a common form of human patients, the recording site at which the fleeting increase epilepsy, temporal lobe epilepsy. Many individuals af-of signal energy exhibited the highest amplitude corre-flicted with temporal lobe …