The Relative Contributions of MRI, SPECT, and PET Imaging in Epilepsy

Abstract

Functional and structural neuroimaging techniques are increasingly indispensable in the evaluation of epileptic patients for localization of the epileptic area as well as for understanding pathophysiology, propagation, and neurochemical correlates of chronic epilepsy. Although interictal single photon emission computed tomography (SPECT) imaging of cerebral blood flow is only moderately sensitive, ictal SPECT markedly improves yield. Positron emission tomography (PET) imaging of interictal cerebral metabolism is more sensitive than measurement of blood flow in temporal lobe epilepsy. Furthermore, PET has greater spatial resolution and versatility in that multiple tracers can image various aspects of cerebral function. Interpretation of all types of functional imaging studies is difficult and requires knowledge of time of most recent seizure activity and structural correlates. Only magnetic resonance imaging (MRI) can image the structural changes associated with the underlying epileptic process, and quantitative evidence of hippocampal volume loss has been highly correlated with seizure onset in medial temporal structures. Improved resolution and interpretation have made quantitative MRI more sensitive in temporal lobe epilepsy, as judged by pathology. When judged by electroencephalography (EEG), ictal SPECT and interictal PET have the highest sensitivity and specificity for temporal lobe epilepsy; these neuroimaging techniques have lower sensitivity and higher specificity for extratemporal EEG abnormalities. Regardless of the presence of structural abnormalities, functional imaging by PET or SPECT provides complementary information. Ideally these techniques should be used and interpreted together to improve the localization and understanding of epileptic brain.

Presurgical multimodality neuroimaging in electroencephalographic lateralized temporal lobe epilepsy

“…Our results comparing FDG-PET with HV replicate independently those published by Gaillard and colleagues [6]. These results, along with the finding that false lateralizations with FDG-PET are extremely rare in TLE [1,33], indicate that FDG-PET can be used to confirm lateralization when other imaging or clinical findings are equivocal.…”

“…Our results comparing FDG-PET with HV replicate independently those published by Gaillard and colleagues [6]. These results, along with the finding that false lateralizations with FDG-PET are extremely rare in TLE [1,33], indicate that FDG-PET can be used to confirm lateralization when other imaging or clinical findings are equivocal.Using 1 H-MRSI lateralization data together with HV yielded a total MR lateralization sensitivity comparable with that of FDG-PET. As a result, addition of 1 H-MRSI to presurgical MR protocols should add lateralizing data above that of only MRI and eliminate the need for a PET study in additional patients with cryptogenic TLE.…”

The Usefulness of Subtraction Ictal SPECT Coregistered to MRI in Single‐ and Dual‐headed SPECT Cameras in Partial Epilepsy

“…In patients with well-localized TLE, past investigators reported the sensitivity of lateralization of visual inspection of ictal SPECT ranging from 39 to 97% (3,16,25). The sensitivity for localization of the epileptogenic zone of our side-by-side evaluation of ictal and interictal SPECT was 37%, lower than that reported in previous studies (3,16,25).…”

“…The sensitivity for localization of the epileptogenic zone of our side-by-side evaluation of ictal and interictal SPECT was 37%, lower than that reported in previous studies (3,16,25). Differences in study design, including localization criteria, patient groups, SPECT scanner resolution, experience of SPECT interpreters, and type of radiopharmaceutical ligand [ 99m Tc-ethyl cysteinate dimer (ECD) or 99m Tc-HMPAO] make direct comparisons of our study results with those of prior investigators difficult.…”

Achados tomográficos em 1000 pacientes consecutivos com antecedentes de crises epilépticas

“…Na dé-cada de 70, Gastaut 1 já propunha uma avaliação aná-tomo-eletroclínica para a classificação das síndromes epilépticas, tamanha a relevância da TC para o diagnóstico etiológico das mesmas. Atualmente acredita-se que o melhor método para investigação de alterações estruturais em epilepsia seja a ressonância magnética (RM) 2,3 . A TC, contudo, ainda se apresenta como um importante instrumento diagnóstico, particularmente em função da alta sensibilidade na demonstração das calcificações intraparenquimato- sas associadas à neurocisticercose (NC), doença de grande incidência nos paises em desenvolvimento e que se manifesta principalmente na forma de crises epilépticas [4][5][6][7] .…”