Radial, spiral and reverberating waves of spreading depolarization occur in the gyrencephalic brain.
OBJECTIVE
The detection of the hemodynamic and propagation patterns of spreading depolarizations (SDs) in the gyrencephalic brain using intrinsic optical signal imaging (IOS).


METHODS
The convexity of the brain surface was surgically exposed in fourteen male swine. Within the boundaries of this window, brains were immersed and preconditioned with an elevated K(+) concentration (7 mmol/l) in the standard Ringer lactate solution for 30-40 min. SDs were triggered using 3-5 μl of 1 mol/l KCl solution. Changes in tissue absorbency or reflection were registered with a CCD camera at a wavelength of 564 nm (14 nm FWHM), which was mounted 25 cm above the exposed cortex. Additional monitoring by electrocorticography and laser-Doppler was used in a subset of animals (n=7) to validate the detection of SD.


RESULTS
Of 198 SDs quantified in all of the experiments, 187 SDs appeared as radial waves that developed semi-planar fronts. The morphology was affected by the surface of the gyri, the sulci and the pial vessels. Other SD patterns such as spirals and reverberating waves, which have not been described before in gyrencephalic brains, were also observed. Diffusion gradients created in the cortex surface (i.e., KCl concentrations), sulci, vessels and SD-SD interactions make the gyrencephalic brain prone to the appearance of irregular SD waves.


CONCLUSIONS
The gyrencephalic brain is capable of irregular SD propagation patterns. The irregularities of the gyrencephalic brain cortex may promote the presence of re-entrance waves, such as spirals and reverberating waves.
Department of Neurosurgery, University Hospital Heidelberg, Germany. Electronic address: dredgarsantos@hotmail.com.
Edgar
E
Santos
Department of Neurosurgery, University Hospital Heidelberg, Germany.
Michael
M
Schöll
Department of Neurosurgery, University Hospital Heidelberg, Germany.
Renán
R
Sánchez-Porras
Department of Physics, Humboldt Universität zu Berlin, Berlin, Germany.
Markus A
MA
Dahlem
Department of Neurosurgery, University Hospital Heidelberg, Germany.
Humberto
H
Silos
Department of Neurosurgery, University Hospital Heidelberg, Germany.
Andreas
A
Unterberg
Institute for Medical Biometry and Informatics, University of Heidelberg, Germany.
Hartmut
H
Dickhaus
Department of Neurosurgery, University Hospital Heidelberg, Germany.
Oliver W
OW
Sakowitz
D000818:Animals; D002540:Cerebral Cortex / Q000033:anatomy & histology* / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D013181:Cortical Spreading Depression; D004569:Electroencephalography; D007091:Image Processing, Computer-Assisted; D008297:Male; D061848:Optical Imaging; D016612:Paraffin Embedding; D013552:Swine; D058067:Wavelet Analysis