Microsurgical anatomy of the velum interpositum and its related membranous structures

Objective To investigate the micro-anatomic features of the velum interpositum and its related membranous structures.Methods The velum interpositum including its construction,relationship with adjacent membranous structures,and related cisterns were observed in 15 cadaveric brains using an operating microscope.Results Two layers of pia converged near the choroidal fissure to form the tela choroidea.This membrane,as it extended above the third ventricle,was separated into upper and lower layer to constitute the velum interpositum.The upper layer was confluent with the pia covering the splenium,while the lower layer was actually a part of the suprapineal recess.The space between the two layers formed the cisterna velum interpositum,which contained internal cerebral veins and the medial posterior choroidal artery.On the posterior,the cisterna velum interpositum was communicated with the pericallosal cistern.Conclusion The anatomy of the velum interpositum and its surrounding structures was reinvestigated,which may be helpful to approach lesions in the posterior third ventricle. Key words: Third ventricle ;  Micromanipulation ;  Dissection ;  Velum interpositum