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Fixed Brain Dissection

Surgical Correlation


Fixed Brain Dissection. A, The remaining frontoparietal operculum must be taken out from the hemisphere to show the insula and the temporal operculum. With one hand, the frontoparietal operculum must be elevated while excised with a number 10 blade along the superior circular sulcus, from the remaining frontal and parietal lobes. The circular sulcus from insula must be shown in all its length after that, as all the short and long insular gyri as well. B, At the left side of this specimen, no cuts were made in the insular lobe after the frontoparietal operculum was removed. In the right side, after this step, axial cuts from the superior to the inferior aspect of the insular lobe, the central core of the brain, were made to show the deepest structures in the insular lobe and their relations with the ventricular cavity, frontoparietal and temporal operculum. It’s the option A, described in the text. These cuts must be done with the long knife in a lateral to medial way, sparing the thalamus to show the ventricular floor, with the help of a number 10 blade as it gets closer to the ventricles. C, The foramen of Monro is shown with the dissector and the genu of the internal capsule points it, as a useful tip seen in MRI images. From lateral to medial, the insular cortex, the extreme capsule, the claustrum, the external capsule, the putamen, the globus pallidus, the internal capsule, the caudate nucleus, the thalamus, the choroid fissure, and the fornix should be exposed after these axial cuts in the central core, as shown in the picture. D, To expose the temporal horn of the lateral ventricles, a cut with the long knife must be done in the superior temporal sulcus, from lateral to medial, toward the insular cortex, removing the superior temporal gyrus or the temporal operculum. After that, progressively deeper cuts are made from lateral to medial in the temporal lobe pointing the inferior circular sulcus of the insula until the tapetum of the corpus callosum, as the most lateral roof of the temporal horn, is thinned. If it hasn’t been opened yet, it can be gently done with the number 10 blade following the same technique used when the anterior ventricular horn, body of the ventricle and atrium was opened. The choroid fissure, the Amon’s horn, the collateral eminence, the pes hippocampus, the thalamus, the fimbriae, the inferior choroidal point and the amygdala in the anterior wall of the temporal horn should be identified after this step, as shown. (Images courtesy of E de Oliveira)