isthmus of cingulate gyrus isthmus of cingulate gyrus the cingulate gyrus commences below the rostrum of the corpus callosum, curves around in front of the genu, extends along the upper surface of the body, and finally turns downward behind the splenium, where it is connected by a narrow isthmus with the parahippocampal gyrus. isthmus of cingulate gyrus( brodmann area 29)medial surface of left cerebral hemisphere. (isthmus labeled at left center.)detailsidentifierslatinisthmus gyri cingulineuronames163neurolex idbirnlex_1541ta98a14.1.09.232ta25514fma62502anatomical terms of neuroanatomy additional images medial surface of cerebral cortex - gyri isthmus of the cingulate gyrus, medial surface of right hemisphere