The Classical Pathways of Occipital Lobe Epileptic Propagation Revised in the Light of White Matter Dissection

Figure 4

(a) Medial view of a right hemisphere after the initial dissection of cortex of the cingulate gyrus. The whole cingulum (Ci) is exposed with its extension from the subcallosal area to the parahippocampal gyrus (PHG) as the radiation of cingulum (CiR) until the region of the uncus. Posterior with respect to the splenium (Sp) of the corpus callosum (CC), a posterior component of the Ci reaches the cuneal and precuneal cortices, forming the most medial part of the forceps major (FM). (b) After the removal of the Ci and further dissection of the CC, the radiating callosal fibres (CaR) can be demonstrated. Once the hippocampus and the PHG have been removed, the lateral ventricle is opened with choroid plexus (ChP) shown at the medial portion of the trigone. The medial wall of the trigone is composed of callosal fibres of the FM, which end close to the optic radiation (OR) fibres on both sides of the calcarine fissure (CF). (c) The medial wall of the ventricle is opened cutting the FM fibres in order to expose the tapetal callosal fibres, which run within the lateral wall of the ventricle composing the deepest layer of the sagittal stratum of Sachs (SSS). The tapetal fibres end following the OR fibres on the medial surface of the cuneal and lingual regions, partially overlapped with the dorsal component of OR. Fo: fornix; Ac: anterior commissure; Pc: posterior commissure; Mb: mammillary body; BS: brain stem; Tha: thalamus; TP: temporal pole; Un: uncus; DeGy: dentate gyrus; POS: parieto-occipital sulcus; CF: calcarine fissure; PreCu: precuneus; Cu: cuneus; Li: lingula; OP: occipital pole.

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