title: Prospective use of subtraction ictal SPECT coregistered to MRI (SISCOM) in presurgical evaluation of epilepsy.
abstract: OBJECTIVE
  In patients with drug-refractory focal epilepsy, nonlesional magnetic resonance imaging (MRI) or discordant data of presurgical standard investigations leads to failure generating a sufficient hypothesis for electrode implantation or epilepsy surgery. The seizure-onset zone can be further investigated by subtraction ictal single-photon emission computed tomography (SPECT) coregistered to MRI (SISCOM). This is an observational study of a large consecutive cohort of patients undergoing prospective SISCOM to generate hypothesis for electrode implantation or site of epilepsy surgery.
  
  
  METHODS
  One hundred seventy-five consecutive patients undergoing presurgical evaluation with either nonlesional MRI or discordant data of standard investigations preventing the generation of hypothesis for seizure onset were evaluated with SISCOM. Results were compared to gold standard for seizure onset detection, either electrocorticography (ECoG) and/or postoperative outcome.
  
  
  RESULTS
  One hundred thirty patients had successful SPECT injection. Hypothesis for electrode implantation/site of surgery was generated in 74 patients. Forty patients had gold standard comparison. Twenty-eight patients underwent resective surgery. SISCOM was concordant to site of surgery in 82%. An additional 12 patients underwent invasive EEG monitoring but were not suitable for surgery. SISCOM was concordant multifocal in 75%. Two years postsurgical follow-up of 26 patients showed favorable outcome in 22 (Engel class I and class II).
  
  
  CONCLUSIONS
  SISCOM is a highly valuable diagnostic tool to localize the seizure-onset zone in nonlesional and extratemporal epilepsies. Outcome in this patient group was unexpectedly good, even in patients with nonlesional MRI. The high correlation with ECoG and site of successful surgery is a strong indicator that outcome prediction in this patient group should be adapted accordingly, which may encourage more patients to undergo electrode implantation and subsequent successful surgery. Statistical analysis showed that SISCOM with shorter duration of seizures, focal seizures, and lesional MRI was more likely to generate implantation hypothesis.
authors.affiliation: Atkinson Morley Neuroscience Centre, St. George's Hospital, London, United Kingdom. tim.vonoertzen@stgeorges.nhs.uk
authors.forename: Tim J
authors.initials: TJ
authors.lastname: von Oertzen
authors.forename: Florian
authors.initials: F
authors.lastname: Mormann
authors.forename: Horst
authors.initials: H
authors.lastname: Urbach
authors.forename: Karl
authors.initials: K
authors.lastname: Reichmann
authors.forename: Roy
authors.initials: R
authors.lastname: Koenig
authors.forename: Hans
authors.initials: H
authors.lastname: Clusmann
authors.forename: Hans Juergen
authors.initials: HJ
authors.lastname: Biersack
authors.forename: Christian E
authors.initials: CE
authors.lastname: Elger
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging* / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D004569:Electroencephalography; D004827:Epilepsy / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008297:Male; D011300:Preoperative Care; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D013382:Subtraction Technique; D015899:Tomography, Emission-Computed, Single-Photon; D055815:Young Adult