title: A quantitative analysis of cortical spreading depression events in the feline brain characterized with diffusion-weighted MRI.
abstract: Cortical spreading depression (CSD) in the gyrencephalic cat brain was detected with diffusion-weighted echoplanar (DWEP) magnetic resonance imaging (4-8/min for 1-2 hours) using a horizontal imaging plane through the suprasylvian (SG) and marginal gyri. A t-statistic mapping technique allowed a quantitative characterization of the passage of events through single-image pixels (0.15 mm(2)), thus providing a resolution unavailable to previous studies in which time-dependent changes instead were derived from averaging data over relatively large ROIs. Using the enhanced analysis, CSD events initiated by KCl could be quantified for the first time as primary or secondary according to their spatial and temporal features. Primary events covered 26.2 +/- 9.9 mm(2)of cortical surface (mean +/- SD, n = 7 experiments) and propagated rapidly (3.5 +/- 0.65 mm * min(-1)) with a hemispherical geometry. In contrast, the subsequent secondary events were multiple, spatially restricted (covering 7.6 +/- 4.6 mm(2), P < 0.005), slower in propagation (2.6 +/- 0.41 mm * min(-1), P < 0.012), and often confined to the originating gyrus (26 out of 59 events). However, both event types were associated with significantly reduced apparent diffusion coefficients (ADCs; from 800 to approximately 660 x 10(-6) mm(2)* s(-1), P < 0.05) that were similar for both primary (21 +/- 5.1%) and secondary waves (18 +/- 7. 7%) and that had similar durations (full width at half-maximal height: 86 +/- 17 vs. 79 +/- 20 seconds, respectively). These findings associate CSD for the first time with two categories of ADC disturbance that are similar in amplitude and duration but that differ in spatial extent, velocity, and extensiveness of spread.
authors.affiliation: Herchel Smith Laboratory for Medicinal Chemistry, University of Cambridge School of Clinical Medicine, Cambridge, CB2 2PZ, United Kingdom.
authors.forename: K H
authors.initials: KH
authors.lastname: Bockhorst
authors.forename: J M
authors.initials: JM
authors.lastname: Smith
authors.forename: M I
authors.initials: MI
authors.lastname: Smith
authors.forename: D P
authors.initials: DP
authors.lastname: Bradley
authors.forename: G C
authors.initials: GC
authors.lastname: Houston
authors.forename: T A
authors.initials: TA
authors.lastname: Carpenter
authors.forename: L D
authors.initials: LD
authors.lastname: Hall
authors.forename: N G
authors.initials: NG
authors.lastname: Papadakis
authors.forename: A A
authors.initials: AA
authors.lastname: Parsons
authors.forename: C L
authors.initials: CL
authors.lastname: Huang
authors.forename: M F
authors.initials: MF
authors.lastname: James
mesh_terms: D000818:Animals; D001931:Brain Mapping / Q000379:methods; D002415:Cats; D002540:Cerebral Cortex / Q000502:physiology*; D013181:Cortical Spreading Depression; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D023421:Models, Animal; D011336:Probability; D012680:Sensitivity and Specificity