The rate of contradictory lateralization of the epileptic seizure onset zone between ictal and interictal brain perfusion SPECT

Ziel/Aim Ictal and interictal brain perfusion SPECT are widely used for the identification of the seizure onset zone (SOZ) in presurgical evaluation of epilepsy patients. Ictal SPECT provides higher sensitivity for this task. Aim of this retrospective study was to estimate the rate of contradictory SOZ lateralization between ictal and interictal SPECT in a large clinical patient sample.

Methodik/Methods Our database was searched for patients in whom ictal and interictal brain perfusion SPECT had been performed for presurgical evaluation of suspected unifocal epilepsy. 193 patients with both SPECT images and structural MRI of the brain were included (38.5 ± 14.7 years, 47.7 % females). Ictal and interictal SPECT had been performed with ^99mTc-HMPAO in 78.2 % and ^99mTc-ECD in 21.8 %. SPECT images were coregistered and then stereotactically normalized to MNI space using SPM12. Lateralization of the SOZ was determined by an experienced reader using standardized side-by-side display of the individual MRI with the ictal or interictal SPECT, in separate reading sessions and randomized order.

Ergebnisse/Results Ictal/interictal SPECT was lateralizing (left or right) in 74.6/30.1 % of the patients. Both ictal and interictal SPECT were lateralizing in 23.8 % of the patients. The lateralization was contradictory between ictal and interictal SPECT (one left, the other right) in 65.2 % of these patients (15.5 % of all patients). Six of the patients with contradictory lateralization had good clinical outcome (Engel Ia-d) 12 months after epilepsy surgery. Ictal/interictal SPECT lateralized the SOZ in the operated hemisphere in 4/2 of these 6 patients, respectively.

Schlussfolgerungen/Conclusions The findings of this study are in line with higher sensitivity of ictal SPECT for identification of the SOZ in presurgical evaluation of epilepsy patients. In addition, they demonstrate a considerable proportion of cases with contradictory lateralization between ictal and interictal SPECT. This demonstrates the relevance of the combination of both SPECT.

Publication History

Article published online:
08 April 2021