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. 2018 Aug;129(8):1651-1657.
doi: 10.1016/j.clinph.2018.05.010. Epub 2018 Jun 6.

Magnetoencephalography and ictal SPECT in patients with failed epilepsy surgery

Riёm El Tahry  1 , Z Irene Wang  2 , Aung Thandar  3 , Irina Podkorytova  4 , Balu Krishnan  3 , Simon Tousseyn  5 , Wu Guiyun  3 , Richard C Burgess  3 , Andreas V Alexopoulos  3
Affiliations

Magnetoencephalography and ictal SPECT in patients with failed epilepsy surgery

Riёm El Tahry et al. Clin Neurophysiol. 2018 Aug.

Abstract

Objective: Selected patients with intractable focal epilepsy who have failed a previous epilepsy surgery can become seizure-free with reoperation. Preoperative evaluation is exceedingly challenging in this cohort. We aim to investigate the diagnostic value of two noninvasive approaches, magnetoencephalography (MEG) and ictal single-photon emission computed tomography (SPECT), in patients with failed epilepsy surgery.

Methods: We retrospectively included a consecutive cohort of patients who failed prior resective epilepsy surgery, underwent re-evaluation including MEG and ictal SPECT, and had another surgery after the re-evaluation. The relationship between resection and localization from each test was determined, and their association with seizure outcomes was analyzed.

Results: A total of 46 patients were included; 21 (46%) were seizure-free at 1-year followup after reoperation. Twenty-seven (58%) had a positive MEG and 31 (67%) had a positive ictal SPECT. The resection of MEG foci was significantly associated with seizure-free outcome (p = 0.002). Overlap of ictal SPECT hyperperfusion zones with resection was significantly associated with seizure-free outcome in the subgroup of patients with injection time ≤20 seconds(p = 0.03), but did not show significant association in the overall cohort (p = 0.46) although all injections were ictal. Patients whose MEG and ictal SPECT were concordant on a sublobar level had a significantly higher chance of seizure freedom (p = 0.05).

Conclusions: MEG alone achieved successful localization in patients with failed epilepsy surgery with a statistical significance. Only ictal SPECT with early injection (≤20 seconds) had good localization value. Sublobar concordance between both tests was significantly associated with seizure freedom. SPECT can provide essential information in MEG-negative cases and vice versa.

Significance: Our results emphasize the importance of considering a multimodal presurgical evaluation including MEG and SPECT in all patients with a previous failed epilepsy surgery.

Keywords: Epilepsy; Failed surgery; MEG; SPECT.

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