Microsurgical anatomy of fornix and its application in surgery of transcallosal-interforniceal approach

Objective To investigate the microsurgical anatomical structures of fornix and provide the anatomical basis for the surgery of transcallosal-interforniceal approach to the third ventricle.Methods (1) The surgery of transcallosal-interforniceal approach was performed on 15 formalin-fixed and dye-injected cadaveric head specimens.The microsurgical anatomy structures of the fornix were observed and measured by microscopes.Subsequently,the measured data was analyzed; (2) The 50 midline sagittal T1-weighted MRI of normal adults with average age of 36 years old and the relationship between the fornix and the corpus callosum were studied.Results (1) The fornix originated from the bottom of the temporal horn and the ventricle surface of the hippocampus and terminated in mammillary body.It presented C shape around the thalamus at the medial side of the medial wall of the lateral ventricle.There were many important nerves and vascular structures surrounding it.(2)The measured data obtained through the surgery of transcallosal-interforniceal approach:the distance between the posterior margin of the incision in corpus callosum and the borderline of fornix connected with corpus callosum was 16.26(11.72-22.04) mm,the height of the septum pellucidum was 13.58 (12.46-14.16) mm,the thickness of the fornix was 3.14(2.86-4.06) mm,the transverse diameter of the foramen of Monro was 3.22(1.86-4.62) mm.(3) The relative position of the fornix and the corpus callosum:type anterior cross,type standard cross and type posterior cross were 14(28％),29(56％) and 9(14％) respectively.Conclusions The anatomical structures of the fornix were complex,morphology and close association with the microstructures of the third ventricle.The understandings of the microanatomy of the fornix and sufficient preoperative evaluation had important significance for surgery of transcallosal-interforniceal approach. Key words: Fornix;  Microsurgical anatomy;  Third ventricle;  Transcallosal-interforniceal approach