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Choroid plexus

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Main article: Cerebral ventricles
Brain: Choroid plexus
Scheme of roof of fourth ventricle. The arrow is in the foramen of Magendie.
1: inferior medullary velum
2: Choroid plexus
3: Cerebellomedullary cistern of subarachnoid cavity
4: Central canal
5: Corpora quadrigemina
6: Cerebral peduncle
7: Superior medullary velum
8: Ependymal lining of ventricle
9: Pontine cistern of subarachnoid cavity
Coronal section of lateral and third ventricles.
Latin plexus choroideus
Gray's subject #187 798
Part of
BrainInfo/UW ancil-456
MeSH A08.

The choroid plexus is the area on the ventricles of the brain where cerebrospinal fluid (CSF) is produced by modified ependymal cells.

Choroid plexus is present in all components of the ventricular system except for the cerebral aqueduct and the occipital and frontal horns of the lateral ventricles.

It is found in the superior part of the inferior horn of the lateral ventricles. It follows up along this boundary, continuous with the inferior of the body of the lateral ventricles. It passes into the interventricular foramen, and is present at the top of the third ventricle.

There is also choroid plexus on the fourth ventricle, on the section closest to the bottom half of the cerebellum.

Structure of the choroid plexus

The choroid plexus consists of many capillaries, separated from the subarachnoid space by pia mater and choroid ependymal cells. Liquid filters through these cells from blood to become cerebrospinal fluid. There is also much active transport of substances into, and out of, the CSF as it is made.


During embryological development, some fetuses may form choroid plexus cysts. These fluid-filled cysts can be detected by a level II ultrasound (18-20 weeks gestation). The finding is relatively common, with a prevalence of ~1%. Choroid plexus cysts (CPC) can be an isolated finding, which confers a 1-12% (variable based on population studied) risk of fetal aneuploidy. The risk of aneuploidy increases to 10.5-12% if other risk factors or ultrasound findings are noted. The size, bilaterality, disappearance/progression of the CPC, and position of the CPC do not have any affect on the risk of aneuploidy. 44-50% of trisomy 18 cases will present with CPC, and 1.4% of trisomy 21 (Down syndrome) cases will present with CPC. ~75% of abnormal karyotypes (obtained by chorionic villus sampling or amniocentesis) associated with CPCs are trisomy 18, while the remainder are trisomy 21. (Drugan et al, 2000, American Journal of Medical Genetics)

CPCs typically disappear later during pregnancy, and are considered soft markers. They are likely harmless, and studies have shown that they have no effect on infant and early childhood development (Digiovanni et al, 1997, Obstetrics and Gynecology).

Additional images

External links

  • MedPix Images of Choroid Plexus

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