Endoscopic anatomy of the velum interpositum: A sequential descriptive anatomical study

BACKGROUND The velum interpositum and structures lying within and over it undergo morbid anatomical changes with hydrocephalus that have not been mentioned in the literature. OBJECTIVES The aim of this article is to describe the diverse endoscopic anatomical findings for this surgically important region. MATERIALS AND METHODS One thousand five hundred and twenty cranial endoscopic procedures performed from September 1993 till March 2011 have been retrospectively reviewed. Anatomical `situm and covering layers have been reported in 40 cases. RESULTS The changes of the velum interpositum have four patterns. These are 1-Distraction mounting to disruption of layers, 2-Reverse in the normal curvature, 3-Reverse of the triangular shape with change in size, and 4-Cystic dilatation causing hydrocephalus. CONCLUSION The velum interpositum and roof of the third ventricle are sites of changes associated with hydrocephalus that show specific patterns described in a sequential anatomical study.