86 However, it is assumed that the epileptic discharge is more sustained within the epileptogenic zone, and that this should translate into greater hyperperfusion in this region than in areas of seizure propagation. This is only partly confirmed by empirical evidence, derived from the comparison of ictal SPECT data with that of other investigations, including intracranial EEG recordings and surgical results. Indeed, a few papers have looked at the correspondence between the ictal onset, zone as defined by invasive

EEG investigation, and ictal hyperperfusion, and reported variable degrees of concordance or overlap between the two.87 According to these results, the role of Inhibitors,research,lifescience,medical ictal SPECT in surgical candidates who would otherwise require intracranial LEG recordings seems rather to help optimize the placement of the Inhibitors,research,lifescience,medical intracranial electrodes than to replace this invasive investigation.88,89 For instance, in a. recent series of 26 patients who benefited from SISCOM and subsequent invasive EEG, the former was found to modify the placement of intracranial electrodes in 58% of cases.88 Like FDG-PET, ictal SPECT might also help to detect subtle focal cortical dysplasia not readily detectable on MRI,90 and to predict Inhibitors,research,lifescience,medical the chance of postoperative seizure freedom.91,92 In particular, in patients with a normal MRI or an extensive malformation of cortical

development, the more complete the resection of the brain

region showing ictal hyperperfusion, the better the surgical outcome.91,92 However, a complete resection of the SISCOM focus does not. seem to be mandatory to achieve complete seizure freedom in patients with focal cortical dysplasia.90 As detailed above, Inhibitors,research,lifescience,medical the potential clinical utility of ictal SPECT appears to primarily lie in patients with a normal MRI as well as in the prediction of surgical Inhibitors,research,lifescience,medical outcome, two issues that have also proved to be the most, relevant clinical indications for FDG-PET. The two investigations have been directly compared with each other in several studies.56,57,93-96. They appear to provide comparable localizing information in a majority of Brefeldin_A cases, but. can also point at strikingly different regions in a minority of patients.56,57 Ictal SPECT might be more sensitive than FDG-PET in epileptogenic zones involving the parietal and occipital lobes,94 and more appropriate for evaluating the epilcptogenicity of large malformation of cortical development.91 Conversely, in one of the largest studies of patients with a normal MRI, FDG-PET was found to be superior to ictal SPECT for predicting postoperative seizure outcome.57 Furthermore, FDG-PET remains more readily available than ictal SPECT in most, epilepsy surgery centers. At the present time, there is no consensus regarding the clinical situations where these two investigations should be combined.