USEFULNESS OF ICTAL AND INTERICTAL TC-99M ETHYL CYSTEINATE DIMER SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY IN PATIENTS WITH REFRACTORY PARTIAL EPILEPSY

Purpose: Ictal perfusion single photon emission computed tomography (S PECT), using HMPAO, has been shown to localize epileptic foci in simil ar to 90% of studies. Unfortunately, HMPAO decomposes rapidly, preclud ing the performance of ictal studies. Ethyl cysteinate dimer (ECD) is a SPECT perfusion agent recently approved by the Food and Drug Adminis tration. After preparation, this compound is stable for similar to 6 h . facilitating the performance of ictal studies.Methods: In a prospect ive, open-label, uncontrolled, non randomized study, we evaluated the potential benefits of the use of Tc-99m-ECD SPECT for lateralization o f the epileptic focus. Ten consecutive adult epilepsy surgery candidat es were studied with ictal and interictal Tc-99m-ECD SPECT. Results: T he mean delay between seizure onset and ictal SPECT injection was 23.2 s. The mean seizure duration was 84.1 s. Ictal studies agreement betw een the epilepsy focus and area of hyperperfusion was evident in 8 of 10 cases, In one case, SPECT was lateralized in a patient with bilater al temporal lobe epilepsy (TLE); however, hyperperfusion was observed on the same side of that particular seizure. In another case, there wa s location disagreement, Interictal SPECT showed focal hypoperfusion i n three cases. Conclusions: Tc-99m-ECD proved to be an optimal tracer for ictal studies. Although this is a small series, the results of ict al and interictal findings using Tc-99m-ECD are similar to those repor ted with Tc-99m-HMPAO. Because Tc-99m-ECD has a longer decomposition t ime, true ictal studies are easier to obtain. This new tracer will pro bably allow the use ofictal SPECT to become widely accepted in most ep ilepsy centers.