Editors’ Commentary 4

Abstract

The discussion on the first two contributions centered around practical questions such as the biocompatibility of recording devices and how such information can be best achieved. The announcement that mini- and microelectrodes for ion-activity recording purposes might be available in the near future (which can be combined with some conventional electrodes used in SEEG) raised great expectations with a view toward future research in human epilepsy. Expectations were also directed towards MR spectroscopy, which may be used to study energy states by measuring31P and pH, despite poor spatial resolution at present. The UCLA experience with PET, which has been used to assess local changes in cerebral blood flow, blood volume, oxygen extraction, pH, protein synthesis, receptor binding, and oxygen and glucose metabolic rates (Mazziota and Engel 1985), demonstrated the value of this new technique both for further research into basic mechanisms of epilepsy and for the noninvasive evaluation of candidates for surgical treatment. In epilepsy most PET studies have measured glucose metabolism. Although a high correlation between the site of the interictal hypometabolic region and the site of ictal onset, recorded with scalp or depth EEG, was noted (Mazziota and Engel 1985), the use of PET in the ictal state for the purpose of localization is limited (Sperling et al. 1987). Current PET techniques require a nearby cyclotron, which is inordinate for many institutions. Although less expensive stand-alone medical cyclotrons may soon be available, SPECT is considerably less costly than PET and has therefore the potential for more wide-spread use. At the Zurich symposium SPECT was not specially represented. This was thought to be justified by the fact that only blood flow can be measured with the tracers now available. The discussion, however, revealed a strong interest in this technique. In particular, the advantages and disadvantages of the two detector types (rotating gamma camera vs that utilizing four sets of sodium iodide crystal scintillation detectors in a square arrangement that rotate about the subject’s head) and the various tracers including 123I-N-isopropyl-iodoamphetamine (IMP), 123I-hydroxyiodopropyl-dianine (HIPDM), and 133Xenon were discussed.