Mark D. Holmes MD
Professor, Department of Neurology
Regional Epilepsy Center
University of Washington, Seattle WA
The evaluation of a person with epilepsy requires a thorough assessment, including a detailed clinical examination, and use of several laboratory studies, especially brain magnetic resonance imaging (MRI), and, depending upon circumstances, neuropsychological testing, and a variety of hematologic and biochemical assays. However, the single most important laboratory study in understanding the nature of the seizure disorder in the affected patient remains, more than 70 after its invention, the electroencephalogram (EEG), The EEG records the electrical activity of the brain, and discloses the abnormal electrical patterns which are the hallmarks of the fundamental disturbance in epilepsy. Regardless of this critical role, standard EEG nevertheless has some severe limitations. One of these is that typically only 16-21 electrodes are applied to the scalp in conventional recordings, a practice that leads to relatively large distances between the recording electrodes. This, in turn, results in the long-held observation that localization of abnormal findings from standard EEG is usually very poor.