Morphologic Variations of the Collateral Sulcus on the Mediobasal Region of the Temporal Lobe: An Anatomical Study

Objective The fusiform gyrus and the collateral sulcus are the anatomical structures located in the temporobasal region. In this study, the topographic anatomy of the fusiform gyrus and the collateral sulcus is detailed to make a contribution for a successful course of temporal lobe surgery. Methods We studied the basal surface of the temporal lobes of 38 formalin-fixed adult human brain specimens. In the morphometric analysis, the distance between anterior and posterior transverse collateral sulcus and the distance between the occipitotemporal sulcus and fusiform apex were used as parameters. The topographic anatomy of collateral sulcus was identified in detail, and 4 sulcal patterns were used to classify the sulcal arrangement of basal surface of temporal lobe in each hemisphere: type 1, single-branch and unbroken collateral sulcus with no connection; type 2, continuous with the rhinal sulcus; type 3, continuous with the occipitotemporal sulcus and; type 4, continuous with both rhinal and occipitotemporal sulcus. Results The current study showed that type 1 was the pattern seen most frequently (42.1%, 16/38), whereas type 4 was the least (7.9%, 3/38). Overall, 63.2% (12/19) of subjects had the same sulcal pattern in both temporal lobes. The morphometric analysis showed that the mean distance between anterior and posterior transverse collateral sulcus was 50 ± 16.2 mm and the mean distance between occipitotemporal sulcus and fusiform apex was 26 ± 8.4 mm. Conclusions The topographic anatomy of the collateral sulcus with its surrounding structures is detailed in this study. This study clarifies and supplements the knowledge presently available to help develop a more feasible surgical concept.