[velum, Latin = veil]
= small triangular (on axial view) membrane containing a closed space between the 2 layers of tela choroidea in the roof of the 3rd ventricle
Borders:
- above: columns of fornices + hippocampal commissure
- below: tela choroidea of 3rd ventricle, internal cerebral veins
- lateral: thalamus
- posterior: splenium of corpus callosum
Cavum Veli Interpositi
= anatomic variant characterized by dilated CSF space of the cistern of the velum interpositum / extension of quadrigeminal plate cistern above 3rd ventricle
Cause: abnormal separation of crura of fornices
- triangular-shaped CSF space / cyst in pineal region
- above tela choroidea of 3rd ventricle
- below columns of fornices
- separated from cavum vergae by crura of fornices