title: Metabolic Correlates of the Ictal-Interictal Continuum: FDG-PET During Continuous EEG.
abstract: Ictal-interictal continuum (IIC) continuous EEG (cEEG) patterns including periodic discharges and rhythmic delta activity are associated with poor outcome and in the appropriate clinical context, IIC patterns may represent "electroclinical" status epilepticus (SE). To clarify the significance of IIC patterns and their relationship to "electrographic" SE, we investigated FDG-PET imaging as a complementary metabolic biomarker of SE among patients with IIC patterns.
  
  
  
  A single-center prospective clinical database was ascertained for patients undergoing FDG-PET during cEEG. Following MRI-PET co-registration, the maximum standardized uptake value in cortical and subcortical regions was compared to contralateral homologous and cerebellar regions. Consensus cEEG review and clinical rating of etiology and treatment response were performed retrospectively with blinding. Electrographic SE was classified as discrete seizures without interictal recovery or >3-Hz rhythmic IIC patterns. Electroclinical SE was classified as IIC patterns with electrographic and clinical response to anticonvulsants; clonic activity; or persistent post-ictal encephalopathy.
  
  
  
  Eighteen hospitalized subjects underwent FDG-PET during contemporaneous IIC patterns attributed to structural lesions (44 %), neuroinflammatory/neuroinfectious disease (39 %), or epilepsy (11 %). FDG-PET hypermetabolism was common (61 %) and predicted electrographic or electroclinical SE (sensitivity 79 % [95 % CI 53-93 %] and specificity 100 % [95 % CI 51-100 %]; p = 0.01). Excluding electrographic SE, hypermetabolism also predicted electroclinical SE (sensitivity 80 % [95 % CI 44-94 %] and specificity 100 % [95 % CI 51-100 %]; p = 0.01).
  
  
  
  In hospitalized patients with IIC EEG patterns, FDG-PET hypermetabolism is common and is a candidate metabolic biomarker of electrographic SE or electroclinical SE.
authors.affiliation: Department of Neurology, Massachusetts General Hospital (MGH), 55 Fruit Street, Wang 735, Boston, MA, 02114, USA. astruck@mgh.harvard.edu.
authors.forename: Aaron F
authors.initials: AF
authors.lastname: Struck
authors.affiliation: Department of Neurology, Massachusetts General Hospital (MGH), 55 Fruit Street, Wang 735, Boston, MA, 02114, USA.
authors.forename: M Brandon
authors.initials: MB
authors.lastname: Westover
authors.affiliation: Department of Radiology, University of Wisconsin, Madison, WI, USA.
authors.forename: Lance T
authors.initials: LT
authors.lastname: Hall
authors.affiliation: Department of Neurology, Massachusetts General Hospital (MGH), 55 Fruit Street, Wang 735, Boston, MA, 02114, USA.
authors.forename: Gina M
authors.initials: GM
authors.lastname: Deck
authors.affiliation: Department of Neurology, Massachusetts General Hospital (MGH), 55 Fruit Street, Wang 735, Boston, MA, 02114, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Cole
authors.affiliation: Department of Neurology, Massachusetts General Hospital (MGH), 55 Fruit Street, Wang 735, Boston, MA, 02114, USA.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Rosenthal
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000378:metabolism; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D013226:Status Epilepticus / Q000145:classification / Q000378:metabolism* / Q000503:physiopathology*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: EEG; FDG-PET; Ictal-interictal continuum; Status epilepticus