The velum interpositum revisited and redefined.

Area of Science:

• Neuroanatomy
• Neurosurgery
• Vascular Anatomy

Background:

• The velum interpositum (VI) is often described with limited detail in neuroanatomical literature.
• Understanding the VI is crucial due to its potential clinical and surgical relevance.

Purpose of the Study:

• To provide a detailed anatomical description of the velum interpositum (VI).
• To clarify the relationship between the VI and the choroid plexus of the lateral and third ventricles.

Main Methods:

• Detailed dissection of the VI in 20 adult cadaveric brains (10 male, 10 female) using an interhemispheric transcollosal approach.
• Observation of VI attachment sites and continuations.
• Measurement of VI length and width.

Main Results:

• The VI extends laterally, becoming continuous with the choroid plexus of the lateral ventricles.
• The choroid plexus of the lateral and third ventricles are a single tissue layer arising from the VI.
• The VI is adherent to, but not fused with, the fornix, pineal gland, and habenula commissure.

Conclusions:

• The supratentorial choroid plexus is a vascular extension of the VI.
• There is no distinct choroid plexus of the third ventricle separate from the VI.
• Identified clear surgical planes between the VI and adjacent structures, beneficial for neurosurgeons and clinicians.