Magnetoencephalography and Ictal SPECT in Patients with Failed Epilepsy Surgery

Publication date: Available online 6 June 2018
Source:Clinical Neurophysiology
Author(s): Riem El Tahry, Z. Irene Wang, Aung Thandar, Irina Podkorytova, Balu Krishnan, Simon Tousseyn, Wu Guiyun, Richard C. Burgess, Andreas Alexopoulos
ObjectiveSelected 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.MethodsWe 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.ResultsA total of 46 patients were included; 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 significantly correlated with seizure-free outcome (p=0.002). Overlap of ictal SPECT hyperperfusion zones with resection significantly correlated with seizure-free outcome in the subgroup of patients with injection time ≤ 20 sec (p=0.03), but did not show significant correlation 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).ConclusionsMEG alone achieved successful localization in patients with failed epilepsy surgery with a statistical significance.Only ictal SPECT with early injection (≤ 20 sec) had good localization value. Sublobar concordance between both tests correlated significantly with seizure freedom. SPECT can provide essential information in MEG-negative cases and vice versa.SignificanceOur results emphasize the importance of considering a multimodal presurgical evaluation including MEG and SPECT in all patients with a previous failed epilepsy surgery.



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