Abstracts

Epileptic spasms (ES) are often difficult to abolish with medical treatment. Surgical treatment of ES is often guided only by MRI lesions or areas of hypometabolism on Positron Emission Tomography scans (PET). Over the past few years a renewed interest has surfaced on the surgical treatment of ES based on chronic invasive EEG with subdural and depth electrodes., We describe three cases of ES in which invasive monitoring was performed in preparation for surgical treatment of ES. Xltek and telefactor equipment were used with sampling rates of 300 Hz. The ictal patterns and their spread on invasive EEG were noted. The latter were compared with the ones seen during partial seizures and and with the published report of ES[apos]s captured in subdural recordings (Asano et al [italic]Epilepsia. 46:1086-97, 2005).[/italic], One case showed fast activity and a leading spike which was more prominent in an area which was not in direct contact with the MRI lesion. In spite of that the patient became seizure-free after the removal of the lesion and surrounding tissue (the leading spike area was not removed).
The second case was a patient with ES and right sided pachygyria who showed bilateral fast activity during the ES on the EEG recorded through bilateral fronto-temporo-parietal strips. Bilateral synchronous leading spikes were noted. Partial seizures with left side onset were also recorded so resective surgery was not performed.
The third case was a patient that we briefly mentioned in a prior publication (de Menezes and Rho Epilepsia 2002;43:623-30). He had a left temporo-parietal cortical dysplasia. ES[apos]s captured through a subdural grid, were associated with diffuse 20-30 Hz activity. Subtotal left temporo-parietal resection of this patient[apos]s lesion where prominent fast activity was seen rendered him seizure-free on anti-seizure medications., These three cases demonstrate some of the challenges of analyzing the area of seizure onset of ES. Quick spread of fast (beta-gamma) frequency ictal cortical activity makes localization difficult. When fast activity appears almost simultaneously in more than one site, a source of ictal activity between these electrodes should be suspected. Due to the limitations of the current EEG technology one should always take in consideration the MRI lesion, areas of hypometabolism on PET, fast activity location and the leading spike on the invasive EEG. One should also keep in mind the regions that were not sampled by the grids and strips. None of these factors alone can completely predict a good outcome after resective surgery for ES. Future research using EEG equipment with higher sampling rates thus allowing reporting of higher frequency information may be helpful.,