Overview
The choroid plexus is a complex capillary network lined by specialised ependymal cells which resides in the pia mater. The ependymal cells are essential in the production of CSF, secreting up to 500 mL per day in adult brains. The choroid plexus forms the blood-CSF barrier along with the arachanoid mater to create a pair of membranes that separate the blood from the CSF.
CSF Flow
- Cerebrospinal fluid flows to the third ventricle from the lateral ventricles via the right and left interventricular foramen of Monro.
- CSF then flows from the third to the fourth ventricle via the cerebral aqueduct of Sylvius.
- Lastly, CSF flows from the fourth ventricle to the subarachnoid space via the foramen of Magendie medially and via the foramen of Luschka laterally.
- Once CSF is in the subarachnoid space, it may be reabsorbed via arachnoid granulations and ultimately drain into the dural venous sinuses.
Locations
Choroid plexi are located in each of the four ventricles.
- Lateral ventricle – Found in the body, atrium and inferior horn. No choroid plexus in the anterior horn
- Third Ventricle – Small amount in the roof that is continuous with that in the body via the interventricular foramina
- Fourth ventricle – Found in the roof
Arterial Supply
- Anterior choroidal artery – most distal branch of the internal carotid artery, supplies the choroid plexus in the lateral ventricles
- Posterior choroidal artery – branch of the posterior cerebral artery supplies the choroid plexus primarily in the third ventricle but also has a minor role in supplying the choroid plexus in the lateral ventricles
- Anterior inferior cerebellar artery – branch from the basilar artery, supplies the choroid plexus in the fourth ventricle
- Posterior inferior cerebellar artery – branche of the vertebral artery, supplies the choroid plexus in the fourth ventricle
Development
- Ventricular development coincides with the development of the brain.
- The choroid plexus has both ectodermal and mesodermal components and begins development across the dorsal axis of the neural tube.
- Once the neural tube closes, the choroid plexus of the fourth ventricle is the first to appear around the ninth week of gestation, followed by the simultaneous development of the choroid plexus in the lateral and third ventricles.
Variants
- Choroid plexus cysts are the most common intraventricular cyst and are present in the antenatal period, which usually by week 28 of gestation but may persist until adulthood without any clinical significance