Defining the relationship of the optic radiation to the roof and floor of the ventricular atrium: a focused microanatomical study.

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The authors investigated the specific topographic relationship of the optic radiation fibers to the roof and floor of the ventricular atrium because the current literature is ambiguous. Thirty-five normal, adult, formalin-fixed cerebral hemispheres and 30 focused MRI slices at the level of the atrium were included in the study. The correlative anatomy of the optic radiation with regard to the atrial roof and floor was investigated in 15 specimens, each through focused fiber microdissections. The remaining 5 hemispheres were explored with particular emphasis on the trajectory of the collateral sulcus in relation to the floor of the atrium. In addition, the trajectory of the collateral sulcus was evaluated in 30 MRI scans. The atrial roof was observed to be devoid of optic radiations in all studied hemispheres, whereas the atrial floor was seen to harbor optic fibers on its lateral part. Moreover, the trajectory of the intraparietal sulcus, when followed, was always seen to correspond to the roof of the atrium, thus avoiding the optic pathway, whereas that of the collateral sulcus was found to lead to either the lateral atrial floor or outside the ventricle in 88% of the cases, therefore hitting the visual pathway. Operative corridors accessing the ventricular atrium should be carefully tailored through detailed preoperative planning and effective use of intraoperative navigation to increase patient safety and enhance the surgeon's maneuverability. The authors strongly emphasize the significance of accurate anatomical knowledge.