Experimental Study On The Spreading Cortical Depression In Cat Model By Functional MRI

Part IExpeimental study of feline brain anatomy for the detection ofspreading cortical depression by magnetic resonance imagingObjective To explore appropriate surface gyri and imaging planes which aresuitable for studying spreading cortical depression (SCD) using the noninvasivetechnique of functional magnetic resonance imaging (fMRI) through investigation thefeline surface gross anatomy and sectional anatomy of cat brain on MRI.Methods 6 femal cats were performed with a 1.5T MR imaging unit (SiemensVision 1.5T). The anatomical images included high-resolution T1W images coveringthe whole brain in vertical transverse, sagittal and coronal planes and conventionalT2W images. The anatomic characteristics were studied on each image. After fixation,specimens of feline brain were acquired and the surface gross anatomy were observedand analyzed.Results Cats had a complex gyrencephalic brain with folded cerebral cortex.The marginal and suprasylvian gyri run rostrocaudally, with simple geometric formand superficial situation. The marginal gyrus was the longest one, but it is bounded bythe superior sagittal sinus. The suprasylvian gyrus situated lateral to the marginalgyrus, absence of big bounded vessels, with continuous grey matter lie on either sideof this gyrus. In contrast, the ectosylvian gyrus was too lateral in position and too short for easy imaging access, and lied under the large temporalis muscle. Thetransverse images of the cat brain could reveal the continuity of the grey matterbetween adjacent gyri. But each transverse section displayed a limited region of greymatter only. Images in the sagittal planes could reveal the marginal and suprasylviangyri more fully but one slice provided an image of only one. Images in the coronalplane which include bilateral marginal and suprasylvian gyri could reveal not only thelength of these gyri, but also the relationship of adjacent gyri, and could provide thecontrahemishere as contrast.Conclusion The complex nature of the cat brain makes it appropriate as anexperimental model for SCD investigation. The suprasylvian gyrus is most suitablefor SCD initiation and imaging. The coronal plane which include bilateral marginaland suprasylvian gyri is the ideal imaging plane for SCD study using functional MRI. Partâ…¡Experimental study on spreading cortical depression in catmodel: preliminary results of functional MRIObjective To study the brain functional activation of cat model aboutspreading cortical depression (SCD) induced by KCl stimulation using bloodoxygenation level dependent functional magnetic resonance imaging (BOLD-fMRI) .Methods 6 adult femal cats were anesthetized with ketamine (25mg/kg, i.m.)and chlorpromazine (10mg/kg, i.m.). Craniotomies were performed in both orbitalsinuses, which were then filled with agar (2%in sterile saline) to reduce imagesusceptibility effects between brain and adjacent tissue. A second craniotomy withdurectomy 5mm lateral to the midline and 5mm posterior to the bregma exposed thesurface of the suprasylvian gyri for KCl/agar and sterile saline/agar applicationrespectively. Images were acquired using a 1.5 T super-conducting magnet (SiemensVision 1.5T). The functional imaging of brain cortex by BOLD technique wasobtained in rest phase, KCl stimulated phase and sterile saline stimulated phaserespectively. The fMRI data was postprocessed using AFNI software. SCD wasvalidated by pathological method.Results The activated regions included the local areas which contacted KCl ofthe suprasylvian gyrus and adjacent areas of the marginal gyrus, and spreaded toposterior part of the marginal gyrus, but there were no activated regions on thecontrahemishere. The signal of fMRI in local active areas immediate and sustainingincreased significantly following the application of KCl showed on time-signalintensity curve. In contrast, the application of sterile saline did not cause the signal offMRI increase. The neurons in the local cortex which stimulated by KCl weresignificant cellular swelling.Conclusion BOLD-fMRI is reliable in detecting the changes of cerebral blood flow (CBF) associated with SCD and is valuable for evaluating SCD. SCD can causesignificant and sustained CBF increase, and alterations in CBF can spread throughsulcus but can not spread to contrahemishere.