Introduction: The transverse cerebral fissure of Bichat is a complex anatomic space formed by a median portion (the velum interpositum) and two oblique lateral branches terminating anteriorly at the medial temporal lobes. Its complexity derives from both its embryological development and from its own nature of "virtual anatomic space". Previous imaging studies have addressed the issue of its anatomical description by using pneumoencephalography or transcranial ultrasound and magnetic resonance imaging especially in those cases with expansile lesions into its anatomical borders.
Methods: We describe the transverse cerebral fissure anatomy in two 20th gestational week fetuses studied with three-tesla MR fetal autopsy with an eye to its embryological development.
Results: We were able to define its anatomical borders thanks to the presence of hemosiderin components that spontaneously layered inside its slit-like boundaries as result of postmortem phenomena and that were depica as T2 hypointensity on MR images.
Conclusions: This Pictorial essay aims to give a concise and novel description of the transverse cerebral fissure: a deep understanding of the Bichat's fissure embryology and anatomy can help to identify and correctly locate abnormalities arising from this virtual anatomic space in the everyday clinical practice.
Keywords: Brain anatomy; Fetal MRI; brain developement; embriology; transverse cerebral fissure.