Ex‐SPECTing success: Predictors of successful SPECT radiotracer injection during presurgical video‐EEG admissions

Abstract

ObjectivesTo determine predictors of successful ictal Single Photon Emission Computed Tomography (SPECT) injections during Epilepsy Monitoring Unit (EMU) admissions for patients undergoing presurgical evaluation for drug resistant focal epilepsy.MethodsIn this retrospective study, consecutive EMU admissions were analysed at a single centre between 2019‐2021. All seizures that occurred during the admission were reviewed. ‘Injectable seizures’ occurred during hours when the radiotracer was available. EMU‐level data were analysed to identify factors predictive of an EMU admission with a successful SPECT injection (successful admission). Seizure‐level data were analysed to identify factors predictive of an ‘injectable seizure’ receiving a SPECT injection during the ictal phase (successful injection). A multivariate generalised linear model was used to identify predictive variables.Results125 EMU admissions involving 103 patients (median 37 years, IQR27.0‐45.5) were analysed. 38.8% of seizures that were eligible for SPECT (n=134) were successfully injected; this represented 17.4% of all seizures (n=298) that occurred during admission. Unsuccessful admissions were most commonly due to a lack of seizures during EMU‐SPECT (19.3%) or no 'injectable seizures’ (62.3%). Successful EMU‐SPECT was associated with baseline seizure frequency >1 per week (95%CI 2.1‐3.0, p <0.001) and focal PET hypometabolism (95%CI 2.0‐3.7, p <0.001). On multivariate analysis, the only factor associated with successful injection was patients being able to indicate they were having a seizure to staff (95%CI 1.0‐4.4, p=0.038).SignificanceCompleting a successful ictal SPECT study remains challenging. Baseline seizure frequency of >1 per‐week, a PET hypometabolic focus and a patient's ability to indicate seizure onset were identified as predictors of success. These findings may assist EMUs in optimising their SPECT protocols, patient selection, and resource allocation.

Determinants of successful ictal SPECT injection in phase 1 epilepsy presurgical evaluation: Findings from the pediatric epilepsy research consortium surgery database project

“…The average length of stay in our study of 4.19 days is similar to other published studies describing SPECT utility. 6,17,18 In our study, the only patient factor that was associated with lack of ictal SPECT success was having Hispanic/ Latino ethnicity. While we did not look for a center effect, how identifying as Hispanic/Latino was associated with SPECT failure remains unclear.…”

“…A past pediatric study from Italy in 2019 6 looking at SISCOM in pediatric DRE indicated that out of 71 hospitalizations for the purpose of obtaining an ictal SPECT only 51 were successful (73%), while other authors 17 describe a rate of 71.9% (64 out of 89 admissions). An adult, single‐center study out of Australia that looked at feasibility of SPECT 18 describes unsuccessful admission rate of 19.3% and thus numbers of successful admissions of 80%. Authors describe SPECT availability as 21 h (Tuesday to Thursday from 9 AM to 4 PM).…”

“… 7 , 19 A single‐center study published in 2023 that included 103 adults from an Australian EMU showed that only 38.8% of all eligible seizures were successfully injected for ictal SPECT. 18 Reasons for injection failures were due to seizures occurring outside of eligible windows (19.3%) or non‐injectable seizures (62.3%). This same study also found PET concordance, high seizure frequency, and ability of patient to indicate seizure onset as factors associated with SPECT success.…”

“…The average length of stay in our study of 4.19 days is similar to other published studies describing SPECT utility. 6 , 17 , 18 …”

“…The adult study by Cosentino et al also found that patients with seizures occurring more than once per week had a higher likelihood of successful ictal SPECT. 18 Duration of VEEG monitoring showed a negative correlation such that longer phase 1 VEEG did not predict ictal SPECT success. Rather, center-specific hours of available SPECT during the VEEG admission contributed to ictal SPECT success.…”