title: Time-threshold curve determined by single photon emission CT in patients with acute middle cerebral artery occlusion.
abstract: OBJECTIVE
  In patients with ischemic stroke, not only the degree of ischemia but also its duration are key determinants of tissue survival. The purpose of this study was to show the synergistic effects of these two factors on tissue survival in humans.
  
  
  METHODS
  We retrospectively reviewed findings in 19 patients with middle cerebral artery occlusion who had clearly defined ischemic duration from onset to angiographic complete recanalization and who underwent pretreatment single photon emission CT. Pretreatment single photon emission CT and final CT scans were compared, and hypoperfusion cortices were divided into reversible and irreversible ischemia. Regions of interest were placed in both irreversible and reversible ischemic cortices, and the residual cerebral blood flow was analyzed by side-to-side comparison with a calculated asymmetry index. To show the relationship between the reversibility of ischemia and the ischemic duration/severity, discriminant analyses were conducted. The analyses were conducted separately using data obtained within 3 hours of ischemic duration and data obtained more than 3 hours after ischemic duration.
  
  
  RESULTS
  Within 3 hours of ischemic duration, analysis revealed a discriminant line of asymmetry index (%) = 21.53 time (h) - 19.15. After more than 3 hours of ischemic duration, it revealed a discriminant line of asymmetry index = 0.50 time + 48.27. These discriminant lines rose rapidly within the first 3 hours after stroke onset and thereafter reached almost a plateau level.
  
  
  CONCLUSIONS
  These pilot data suggest urgency for treatment, less need for triage based on cerebral blood flow measurement during the first few hours, and more time to triage based on cerebral blood flow measurement for patients with later presentations.
authors.affiliation: Department of Neurosurgery, Miyazaki Medical College, Junwakai Memorial Hospital, Miyazaki, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Iseda
authors.forename: Shinichi
authors.initials: S
authors.lastname: Nakano
authors.forename: Takao
authors.initials: T
authors.lastname: Yano
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Wakisaka
mesh_terms: D000208:Acute Disease; D000368:Aged; D000369:Aged, 80 and over; D000800:Angioplasty, Balloon; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000628:therapy; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D020244:Infarction, Middle Cerebral Artery / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging*; D015912:Thrombolytic Therapy; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed