(322) Effect of post-ictal SPECT injection antiseizure drugs (ASDs) on the localization value of SPECT studies and treatment related adverse events: a single center prospective study

Rationale: Ictal single photon emission computed tomography (SPECT), subtraction ictal SPECT co-registered to MRI (SISCOM), and ictal-interictal SPECT analysis by statistical parametric mapping (SPM) are valuable methods for ictal onset zone localization in patients with drug-resistant focal epilepsy. Following ictal SPECT injection, patients are typically resumed on their home antiseizure drug regimen (ASD alone) or additionally intravenous benzodiazepines (ASD+) to minimize risk of breakthrough seizure prior to acquisition of interictal SPECT. Currently, little is known about the effect of these two approaches on the localization value of SPECT studies and treatment related adverse events (TRAEs).

Methods: We conducted a prospective study at Mayo Clinic Florida inpatient epilepsy monitoring unit between January 2017–May 2020. Post ictal SPECT injection, patients were allocated to receive ASD alone or ASD+ as determined by admitting epileptologist practice preference. TRAE information was obtained from surveys at 24 hours and one week post ictal SPECT injection. The two groups were compared for the rate of TRAEs and the concordance of SPECT studies (SPECT, SISCOM, and SPM) with the epilepsy surgical conference consensus or intracranial EEG monitoring (iEEG) findings, when available, as reference. Comparison between the concordances of SPECT studies and interictal positron emission tomography (PET) findings with the reference was performed for the entire cohort.

Results: Twenty-two consecutive patients (19-60 years of age; M/F=1:1) were included: 12 ASD+ and 10 ASD alone. Patient demographics, seizure characteristics, and pre-surgical workup characteristics were similar for the two groups except age of seizure onset (median 12.5 ASD alone vs. 21 ASD+, p-value = 0.03). The localization and lateralization value of SPECT studies was similar in the two groups, except for ictal SPECT, which had higher localization value for ASD alone (30%) vs ASD+ (0%), p-value = 0.04 (Figure 1). Patients in the ASD+ group reported higher rates of dizziness and excessive sedation at 24 hours (p-value = 0.01), but patient perception of seizure control, overmedication, and apprehension at both 24 hours and one week did not differ between both groups. Overall, the localization and lateralization values did not differ among ictal SPECT, SISCOM, SPM, and PET.

Conclusions: Our findings suggest that resumption of ASD alone or ASD+ post-ictal SPECT injection impacts only the localizing value of raw ictal SPECT and not other SPECT studies. Overall, the two methods were equally well tolerated except for the increased rate of drowsiness in the ASD+ group. Given the lower ictal SPECT localization value and the higher drowsiness in the ASD+ group, we recommend resumption of home ASDs alone during inpatient SPECT studies. However, further studies with larger cohorts are needed to confirm our findings and to examine the effect these methods have on post-surgical seizure freedom.

Funding: Please list any funding that was received in support of this abstract.: None
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