title: Repeated ictal SPECT in partial epilepsy patients: SISCOM analysis.
abstract: OBJECTIVE
  Ictal single-photon emission computerized tomography (SPECT) is often nonlocalized in patients with partial epilepsy. We repeated ictal SPECT in patients with partial epilepsy whose first ictal SPECT was nonlocalized. We also performed subtraction ictal SPECT coregistered to magnetic resonance imaging (MRI) (SISCOM) to test the localizability of ictal SPECT.
  
  
  METHODS
  We recruited 69 patients with partial epilepsy (33 male and 36 female, mean plus or minus standard deviation age 29.5 ± 12.2 years), who had a repeated ictal SPECT. Ictal-interictal SPECT subtractions were performed, and the subtracted SPECTs were coregistered with their brain MRI studies. SISCOM results were considered to be localizing when the results were concordant with the final location of the epileptic focus, as determined by the presurgical evaluation. We compared seizure duration, tracer injection time, interictal and ictal scalp electroencephalography (EEG) patterns, presence and time of secondary generalization, and epilepsy classification between the localized and nonlocalized SISCOM groups.
  
  
  RESULTS
  The SISCOM results of the second ictal SPECT were localized in 43 (62.3%) patients and nonlocalized in 26 (37.7%) patients. In the second ictal SPECT, the radiotracer injection time was significantly shorter in the localized group (25.1 ± 8.9 s), as compared to the nonlocalized group (49.2 ± 55.8 s) (p = 0.008). Furthermore, the radiotracer injection time of the second ictal SPECT was significantly shorter than the first ictal SPECT, only in the localized group (36.8 ± 23.8 s in the first and 25.1 ± 8.9 s in the second ictal SPECT in the localized group, p = 0.004). The percent injection time ([(tracer injection time-seizure onset time)/total seizure duration] × 100%) in the second SPECT was significantly shorter in the localized group, as compared to the nonlocalized group (37.9 ± 23.0% in the localized group and 72.3 ± 46.2% in the nonlocalized group, p < 0.001). The localized ictal EEG patterns at the time of injection were more frequent in the localized SISCOM group. The secondary generalization of seizures at the time of injection was more frequent in nonlocalized groups.
  
  
  CONCLUSIONS
  Repeated ictal SPECT with SISCOM analysis is helpful for localizing an epileptic focus in patients with partial epilepsy who have a nonlocalized first ictal SPECT. The most important factor for increasing the localizability of repeated ictal SPECT is early injection time and a localizing ictal EEG pattern at the time of radiotracer injection.
authors.affiliation: Department of Neurology, Chonbuk National University Hospital, Jeonju, Korea.
authors.forename: Jun Young
authors.initials: JY
authors.lastname: Lee
authors.forename: Eun Yeon
authors.initials: EY
authors.lastname: Joo
authors.forename: Hwan Seok
authors.initials: HS
authors.lastname: Park
authors.forename: Pamela
authors.initials: P
authors.lastname: Song
authors.forename: So
authors.initials: S
authors.lastname: Young Byun
authors.forename: Dae Won
authors.initials: DW
authors.lastname: Seo
authors.forename: Seung Bong
authors.initials: SB
authors.lastname: Hong
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology; D001931:Brain Mapping; D004569:Electroencephalography; D004828:Epilepsies, Partial / Q000145:classification / Q000000981:diagnostic imaging* / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D018709:Statistics, Nonparametric; D013382:Subtraction Technique; D015899:Tomography, Emission-Computed, Single-Photon; D055815:Young Adult