Comparison of ictal SPECT and interictal PET in the presurgical evaluation of temporal lobe epilepsy

Abstract

We retrospectively compared ictal technetium 99m hexamethylpropyleneamineoxime single-photon emission computed tomography (SPECT) and interictal 18F-fluorodeoxyglucose positron emission tomography (PET) in 35 patients with well-lateralized temporal lobe epilepsy (TLE). Based on SPECT scans the two observers correctly lateralized seizure foci with certainty in 89% of patients; interobserver agreement was excellent. Both observers incorrectly lateralized the seizure focus on two SPECT scans; one error was explained by rapid electroencephalographic spread to the contralateral side and for the other patient, isotope was injected during a brief aura. Based on PET scans, observers correctly lateralized the foci with certainty in 63% and with lesser confidence in 83%; four incorrect lateralizations were made by one observer and none by the other. PET interobserver disagreement was explained by differences between observers in weighting the relative hypometabolism in medial and lateral temporal regions. The detection rate for PET was lower in the absence of structural imaging abnormalities (60 vs 87%). PET yielded correct lateralizations in the 2 patients for whom SPECT interpretation was difficult. We conclude that both ictal SPECT and interictal PET are sensitive methods for the lateralization of TLE, but SPECT can be interpreted with greater certainty and is more sensitive when magnetic resonance imaging findings are negative. False lateralization is rare with ictal SPECT and can be explained when interpreted in conjunction with electroclinical data. Both investigations have complementary roles when localization is difficult.

Localization of the Epileptogenic Zone by Ictal and Interictal SPECT with 99mTc‐Ethyl Cysteinate Dimer in Patients with Medically Refractory Epilepsy

“…Interictal SPECT, however, both with HMPAO and with ECD, is of limited value in the localization of the epileptogenic zone for surgical decision (3,9-12,15,3 I), as indicated by its relatively low positive predictive value (66.2%, 95% CI 55.6-76.8%). In contrast, ictal studies have been shown to be a highly effective and reliable method for determination of the seizure-onset zone in patients undergoing evaluation for epilepsy surgery, both in TLE (5,6,30) and in epilepsy of extratemporal origin (4,7,8). In our study, ictal SPECT with ECD has confirmed its significantly higher positive predictive value (91.3%) as compared with interictal ECD SPECT (66.2%).…”

The Cost-Effective Use of 18F-FDG PET in the Presurgical Evaluation of Medically Refractory Focal Epilepsy

“…PET produces potentially quantifiable data with a superior spatial resolution to SPECT but less than that of MRI. 18 F-FDG PET images are reliable in lateralizing temporal lobe epilepsy (TLE) in patients without a discrete neocortical mass lesion, with reported sensitivities of 60%-90% and few falsely lateralized cases (5)(6)(7)(8)(9). In addition, 18 F-FDG PET may provide localizing information that is independent of that provided by MRI (9,10) and is prognostic of the patient's seizure outcome (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19).…”

Nuclear Medicine Methods in Epilepsy

“…ECD'nin yüksek kan akımında daha doğrusal ekstraksiyon ve daha uzun süre stabilizasyon zamanı (akuzisyon gerçekleştirmek için daha uzun süre sağlar) gibi üstün özellikleri olsa da HMPAO'nun sensitivitesi daha yüksektir (34). F-18 FDG PET özellikle ekstratemporal lob epilepsisinde iktal SPECT'e yakın sensitiviteye sahiptir (35,36). Ayrıca C-11 FMZ ile yapılan çalışmalar epileptik odak belirlemeye katkısı olabileceğini gösterse de MR'yi normal olan olgularda FMZ PET'in FDG'ye göre yanlış pozitifliklerinin daha fazla olduğu da bildirilmektedir (37,38).…”