Cortical spreading depression in the gyrencephalic feline brain studied by magnetic resonance imaging

1 Time‐lapse diffusion‐weighted magnetic resonance imaging (DWI) was used to detect and characterize complex waves of cortical spreading depression (CSD) evoked with KCl placed upon the suprasylvian gyrus of anaesthetized cats. 2 The time‐lapse representations successfully demonstrated primary CSD waves that propagated with elliptical wavefronts selectively over the ipsilateral cerebral hemispheres with a velocity of 3.8 ± 0.70 mm min−1 (mean ± s.e.m. of 5 experiments). 3 In contrast, the succeeding secondary waves often remained within the originating gyrus, were slower (velocity 2.0 ± 0.18 mm min−1), more fragmented and varied in number. 4 Computed traces of the apparent diffusion coefficients (ADCs) showed negative deflections followed by monotonic decays (amplitudes: primary wave, ‐19.9 ± 2.8 %; subsequent waves, ‐13.6 ± 1.9 %; duration at half‐maximal decay, 150‐200 s) when determined from regions of interest (ROIs) through which both primary and succeeding CSD waves propagated. 5 The passage of both the primary and the succeeding waves often correlated with transient DC potential deflections recorded from the suprasylvian gyrus. 6 The detailed waveforms of the ADC and the T2*‐weighted (blood oxygenation level‐dependent: BOLD) traces showed a clear reciprocal correlation. These imaging features that reflect disturbances in cellular water balance agree closely with BOLD measurements that followed the propagation velocities of the first and subsequent CSD events. They also provide a close physiological correlate for clinical observations of cortical blood flow disturbances associated with human migraine.