= 1.5–3.0 mm thin vertical membrane of triangular shape (when viewed from side)
- connecting corpus callosum to columns of fornix
- forming the medial wall of the lateral ventricles
- separating both anterior horns
Base of triangle: located anteriorly
Apex of triangle: located posteriorly
Five layers (leaves / laminae) of septum:
- CSF in anterior horn of RT lateral ventricle
- ependymal lining (gray matter) of RT lamina
- pial layer (white matter) of RT lamina
- potential space / slitlike cavity / cavum
- pial layer (white matter) of LT lamina
- pial layer (white matter) of RT lamina
- ependymal lining (gray matter) of LT lamina
- ependymal lining (gray matter) of RT lamina
- CSF in anterior horn of LT lateral ventricle
Borders:
below: column + body of fornix
above: corpus callosum
ventral: continuous with precommissural septum + subcallosal gyrus
lateral: wall of lateral ventricles
Function: ?, part of limbic system moderating rage + arousal
= persistence / failure of fusion of potential space (= slitlike cavity = 5th ventricle) between the 2 laminae forming septum pellucidum
Frequency: in 80% of term infants; in 15% of adults
Location: posterior to genu of corpus callosum, inferior to body of corpus callosum, anterosuperior to anterior pillar of fornix
Marker for: cerebral dysfunction
- extends to foramen of Monro
- may dilate + cause obstructive hydrocephalus (rare)
Regression: from back to front as fetus approaches term / in first few weeks after birth
= “6th ventricle”
[Andrea Verga (1811–1895), clinical professor of psychiatry at Ospedale Maggiore in Milan, Italy]
= fluid-filled cavity located posterior to a vertical plane formed by columns of fornix
Frequency: in 30% of term infants; in 15% of adults
Location: posterior to fornix; anterior to splenium of corpus callosum inferior to body of corpus callosum superior to transverse fornix
- posterior midline continuation of cavum septi pellucidi beyond foramen of Monro (= communicates with cavum septi pellucidi)
Regression: cavum vergae (1st) >cavum septi pellucidi (2nd); contracts after about 6th gestational month